Extensible 3D (X3D)
Part 1: Architecture and base components

12 Shape component

--- X3D separator bar ---

cube 12.1 Introduction

12.1.1 Name

The name of this component is "Shape". This name shall be used when referring to this component in the COMPONENT statement (see 7.2.5.4 Component statement).

12.1.2 Overview

This clause describes the Shape component of this part of ISO/IEC 19775. The Shape component defines nodes for associating geometry with their visible properties and the scene environment. Table 12.1 provides links to the major topics in this clause.

Table 12.1 — Topics

cube 12.2 Concepts

12.2.1 Shape characteristics

The Shape node associates a geometry node with nodes that define that geometry's appearance. Shape nodes shall be part of the transformation hierarchy to have any visible result, and the transformation hierarchy shall contain Shape nodes for any geometry to be visible (the only nodes that render visible results are Shape nodes and the background nodes described in 24 Environmental effects). A Shape node contains exactly one geometry node in its geometry field, which is of type X3DGeometryNode. The Shape node descends from the abstract base type X3DShapeNode.

12.2.2 Appearance characteristics

Shape nodes may specify an Appearance node that describes the appearance properties (material, texture and texture transformation) to be applied to the geometry of the Shape. All valid children of the Appearance node descend from the abstract base type X3DAppearanceChildNode.

Nodes of the following types may be specified in the material field of the Appearance node:

This set of nodes may be extended by creating new nodes derived from the X3DMaterialNode abstract base type.

Nodes of the following types may be specified in the backMaterial field of the Appearance node:

This set may be extended by creating new nodes derived from the X3DOneSidedMaterialNode abstract base type.

The Appearance node specifies texture mapping in its texture field. Valid values of the texture field are descendants of X3DTextureNode, including:

This set may be extended by creating new nodes derived from the abstract X3DTextureNode base class as defined in 18.3.2 X3DTextureNode.

Nodes of the type X3DTextureTransformNode may be specified in the textureTransform field of the Appearance node (see 18.3.4 X3DTextureTransformNode), including:

Interaction between the appearance properties and properties specific to geometry nodes are described in 13 Geometry3D component and 14 Geometry2D component.

An Appearance node may specify additional information about the appearance of the corresponding geometry. Special properties may also be defined for geometric areas. These properties are defined in the acousticProperties, fillProperties, lineProperties, and pointProperties fields by the following nodes, respectively:

12.2.3 Two-sided materials

A polygon defines a front face based on the direction of the normal vector. That normal is either explicitly provided by the end user or implicitly calculated by the browser based on the winding rules for the node (for example, see the ccw field on many of the polygonal geometry nodes such as IndexedFaceSet).

The solid field, described in the 11.2.3 Common geometry fields, controls whether the geometry is visible from the back side.

Using the Appearance field backMaterial allows rendering the front and back sides of the polygon with different material properties. It is meaningful only when solid is FALSE, since otherwise the back faces are never rendered. When the solid is TRUE, the value of backMaterial has no effect on rendering.

TwoSidedMaterial (deprecated) provides similar functionality for back faces but is limited to the Phong lighting model.

Figure 12.1 depicts example effects of the Appearance field backMaterial node.

Two-sided material demonstration

Figure 12.1 — Effects of different material properties on front and back sides of the geometry

Several constraints pertain to the backMaterial field value:

In effect, the material and backMaterial nodes may differ only in their numeric fields. For example, front side may have a different diffuseColor than the back side.

To summarize, the following combinations are allowed:

12.2.4 Texture mapping specified in material nodes

The X3DOneSidedMaterialNode and descendants (Material, PhysicalMaterial, UnlitMaterial) introduce a number of fields to modify material parameters using textures. They are consistently defined by a pair of fields like this:

  SFNode   [in,out] xxxTexture        NULL
  SFString [in,out] xxxTextureMapping ""

The field xxxTexture indicates a texture node.

The xxxTextureMapping determines the texture coordinates and texture coordinates transformation for given texture xxxTexture.

The corresponding texture coordinate and texture coordinate transformation nodes have a field mapping that will match the value of the xxxTextureMapping field. See the X3DSingleTextureCoordinateNode and X3DSingleTextureTransformNode definitions.

Multiple textures may use the same texture coordinates and their transformations. For example, it is common that both normalTextureMapping and diffuseTextureMapping are equal, if the graphic artist prepared both normalTexture and diffuseTexture simultaneously, assuming the same mapping.

12.2.4.1 Texture coordinates

Let's define a list of texture coordinates for each geometry node like this:

NOTE  The above definition means that using a MultiTextureCoordinate with exactly one child is equivalent to using this child directly. This is a general rule in X3D 4.0, see also the MultiTextureCoordinate specification for details and an example.

All the X3DSingleTextureCoordinateNode nodes on the list of texture coordinates defined above must have a different mapping value. An exception is the empty mapping value, which may occur many times.

If the xxxTextureMapping field is not empty, it should refer to a corresponding X3DSingleTextureCoordinateNode node on a list of texture coordinates. The corresponding X3DSingleTextureCoordinateNode node must have equal mapping value. If no corresponding X3DSingleTextureCoordinateNode is found on this list, the browser should determine texture coordinates as if xxxTextureMapping would be empty (see below). If multiple X3DSingleTextureCoordinateNode nodes with the same mapping field values are present then the one that is first found on the list of texture coordinates is used.

If the xxxTextureMapping field is empty, then the first item on a list of texture coordinates is used (regardless of the mapping value). Only if no such texture coordinate exists (the list is empty), then then default texture coordinates for the specific geometry node are used.

The algorithm to perform the default texture coordinate calculation is described at each geometry node. For example IndexedFaceSet determines the coordinates based on the local bounding box sizes, Box has the texture applied 6 times on 6 faces etc.

Hint for implementations: This section makes an important guarantee. Generating default texture coordinates only needs to be done when the texCoord field of the geometry is empty, or contains an empty MultiTextureCoordinate node. In all other cases, you know that default texture coordinates are not necessary, because all textures will use one of the coordinates in the texCoord list.

This is an important property, because browsers may want to avoid generating default texture coordinates as it is a time-consuming process (e.g. requires to iterate over vertexes at least twice in case of IndexedFaceSet) and often not necessary (models exported by 3D authoring software typically have all texture coordinates provided in the file).

So we wanted to enable this optimization, and make it easy to detect looking only at texCoord contents. In effect, it doesn't matter what Appearance or material will be used with this geometry node — you can easily avoid most cases when default texture coordinates would be unused just by inspecting the geometry texCoord value.

12.2.4.2 Texture coordinates transformation

Let's define a list of texture transformations for each geometry node like this:

Note that we treat a MultiTextureTransform with a single child always the same as using this child directly. This is a general rule in X3D 4.0, see also the MultiTextureTransform specification for details and an example.

If the xxxTextureMapping field is not empty, it should refer to a corresponding X3DSingleTextureTransformNode node within the list of texture transformations. The corresponding X3DSingleTextureTransformNode node must have equal mapping value. If no such corresponding X3DSingleTextureTransformNode is found, the browser should determine texture transformation as if xxxTextureMapping would be empty (see below). If multiple X3DSingleTextureTransformNode nodes with the same mapping field values are present then the one that is first found on the list of texture transformations is used.

If the xxxTextureMapping is an empty string, then the first item on a list of texture transformations is used (regardless of the mapping value). If the list is empty, no texture transformation is used.

NOTE  Throughout this section, we treat empty string as a special case for xxxTextureMapping and mapping fields. Such mapping names are allowed (they are even the default) but they do not constitute a "match". It would be error-prone if two empty mapping values would match, as it's easy to use them accidentally, since they are the default field values. Instead, empty xxxTextureMapping just indicates "use the first coordinates / transformations" — this is simplest and most natural.

12.2.5 Coexistence of textures specified in material nodes with the "Appearance.texture" field

In X3D 4.0, models can specify textures using the xxxTexture fields inside the various X3DOneSidedMaterialNode descendants. This allows to control every material parameter by a different texture.

Alternatively, models can also use the mechanism known from X3D 3.x, and provide a texture inside the Appearance.texture field. This is also the only way to use the MultiTexture node (which cannot be placed in xxxTexture fields, as it would make implementation complicated).

The exact behavior of MultiTexture node and Appearance.texture is this:

  1. If the Appearance.material is Material, and the Material.diffuseTexture is NULL, then Appearance.texture affects the diffuseParameter for the lighting equation.

    In a way, Appearance.texture performs then the role of Material.diffuseTexture. It can even use MultiTexture to calculate the diffuse parameter by a composition (e.g. addition or multiplication) of other textures.

    The Material.diffuseTextureMapping value doesn't matter in this case.

  2. If the Appearance.material is PhysicalMaterial, and the PhysicalMaterial.baseTexture is NULL, then Appearance.texture affects the baseParameter for the lighting equation.

    The PhysicalMaterial.baseTextureMapping value doesn't matter in this case.

  3. If the Appearance.material is UnlitMaterial, and the UnlitMaterial.emissiveTexture is NULL, then Appearance.texture affects the emissiveParameter for the lighting equation.

    The UnlitMaterial.emissiveTextureMapping value doesn't matter in this case.

  4. Otherwise, if the Appearance.material is NULL, then we behave as if the UnlitMaterial with all fields at default was used. So the Appearance.texture affects the emissiveParameter for the lighting equation, and is used with the unlit lighting model.

Note that when the Appearance.texture is used to calculate one of the parameters described above, the texture coordinates/transformations are determined following the MultiTexture specification. This means that MultiTextureCoordinate and MultiTextureTransform nodes can be used, with the order corresponding to the order of textures inside MultiTexture.texture list. If the Appearance.texture is not MultiTexture then the first set of texture coordinates/transformations are used. See the MultiTextureCoordinate and MultiTextureTransform specification for details.

The 17 Lighting component describes the exact equations to calculate the lighting parameters, consistent with the above description.

cube 12.3 Abstract types

12.3.1 X3DAppearanceChildNode

X3DAppearanceChildNode : X3DNode { 
  SFNode [in,out] metadata NULL [X3DMetadataObject]
}

This is the base node type for the child nodes of the X3DAppearanceNode type.

12.3.2 X3DAppearanceNode

X3DAppearanceNode : X3DNode {
  SFNode [in,out] metadata NULL [X3DMetadataObject]
}

This is the base node type for all Appearance nodes.

12.3.3 X3DMaterialNode

X3DMaterialNode : X3DAppearanceChildNode {
  SFNode [in,out] metadata NULL [X3DMetadataObject]
}

This is the base node type for all material nodes.

There are two direct descendants of this node type:

  1. Abstract X3DOneSidedMaterialNode.

    In turn, the X3DOneSidedMaterialNode is a descendant for all non-abstract and non-deprecated material nodes that you shall use in X3D models:

  2. TwoSidedMaterial (deprecated)

12.3.4 X3DOneSidedMaterialNode

X3DOneSidedMaterialNode : X3DMaterialNode {
  SFColor  [in,out] emissiveColor           0 0 0  [0, 1]
  SFNode   [in,out] emissiveTexture         NULL   [X3DSingleTextureNode]
  SFString [in,out] emissiveTextureMapping  ""

  SFNode   [in,out] metadata                NULL   [X3DMetadataObject]

  SFFloat  [in,out] normalScale             1      [0, ∞)
  SFNode   [in,out] normalTexture           NULL   [X3DSingleTextureNode]
  SFString [in,out] normalTextureMapping    ""
}

This is the base node type for material nodes that describe how the shape looks like from one side.

This node defines common properties for a lighting calculation, but independent of the lighting model (Phong, physically-based, unlit).

This node can be used within Appearance.material or Appearance.backMaterial.

The normalTexture field affects normal vectors information (surface curvature) in the following way:

The emissiveColor, together with emissiveTexture, allow to model "glowing" objects. This can be useful for displaying unlit (pre-lit) models (where the light energy of the room is computed explicitly), or for displaying scientific data. To display an "unlit" object (whose visible color should not be modified by any light in the scene), author can use UnlitMaterial node.

The emissiveTexture RGB channel is multiplied with the emissiveColor to yield the emissiveParameter in the lighting equations.

The meaning of the alpha channel of the emissiveTexture depends on the X3DOneSidedMaterialNode descendant. It is ignored by Material and PhysicalMaterial. It is used, as the transparency factor, by the UnlitMaterial. Across the specification, the treatment of Material.diffuseTexture, PhysicalMaterial.baseTexture and UnlitMaterial.emissiveTexture is consistent: these "main" textures provide the transparency information for given material. For details, refer to the documentation of each X3DOneSidedMaterialNode descendant.

See the section 12.2.4 Texture mapping specified in material nodes for a description how the texture coordinates and texture coordinate transformations are determined based on the xxxTextureMapping fields of this node.

12.3.5 X3DShapeNode

X3DShapeNode : X3DChildNode, X3DBoundedObject {
  SFNode  [in,out] appearance  NULL     [X3DAppearanceNode]
  SFBool  [in,out] bboxDisplay FALSE
  SFBool  [in,out] castShadow  TRUE
  SFNode  [in,out] geometry    NULL     [X3DGeometryNode]
  SFNode  [in,out] metadata    NULL     [X3DMetadataObject]
  SFBool  [in,out] visible     TRUE
  SFVec3f []       bboxCenter  0 0 0    (-∞,∞)
  SFVec3f []       bboxSize    -1 -1 -1 [0,∞) or −1 −1 −1
}

This is the base node type for all Shape nodes.

The visible field determines whether Shape geometry is rendered.

The castShadow field defines whether this Shape casts shadows as produced by lighting nodes. If the visible field is FALSE, then the Shape does not cast any shadows, regardless of the castShadow value.

cube 12.4 Node reference

12.4.1 AcousticProperties

AcousticProperties : X3DAppearanceChildNode  {
  SFFloat  [in,out] absorption  0    [0,1]
  SFString [in,out] description ""
  SFFloat  [in,out] diffuse     0    [0,1]
  SFBool   [in,out] enabled     TRUE
  SFNode   [in,out] metadata    NULL [X3DMetadataObject]
  SFFloat  [in,out] refraction  0    [0,1]
  SFFloat  [in,out] specular    0    [0,1]
}

The AcousticProperties node specifies the interaction of sound waves with the characteristics of objects in the scene. Properties influencing sound propagation include surface-related physical phenomena such as the specular reflection, diffuse reflection, absorption, and refraction coefficients of materials. These coefficient values are expected to fully account for physical and structural characteristics of the associated geometry such as width, height, thickness, shape, softness and/or hardness, and density variations.

The absorption field specifies the sound absorption coefficient of a surface which is the ratio of the sound intensity absorbed or otherwise not reflected by a specific surface that of the initial sound intensity. This characteristic depends on the nature and thickness of the material. Sound energy is partially absorbed when it encounters fibrous or porous materials, panels that have some flexibility, volumes of air that resonate, and openings in room boundaries (e.g. doorways). Moreover, the absorption of sound by a particular shape depends on the angle of incidence and frequency of the sound wave.

The description field specifies a textual description node characteristics. This information is beneficial for authoring, and may be used by optional browser-specific user interfaces that present users with more detailed information about active time-dependent behavior.

The enabled field enables and disables acoustic effects.

The diffuse field describes the diffuse coefficient of sound reflection. This is one of the physical phenomena of sound that occurs when a sound wave strikes a plane surface, and part of the sound energy is reflected back into space in multiple directions.

The refraction field describes the sound refraction coefficient of a medium, which determines the change in propagation direction of a sound wave when it obliquely crosses the boundary between two mediums where its speed is different. These relationships are described by Snell's Law.

The specular field describes the specular coefficient of sound reflection, which is one of the physical phenomena of sound that occurs when a sound wave strikes a plane surface. Part of the sound energy is directly reflected back into space, where the angle of reflection is equal to the angle of incidence.

12.4.2 Appearance

Appearance : X3DAppearanceNode {
  SFNode   [in,out] acousticProperties NULL   [AcousticProperties]
  SFFloat  [in,out] alphaCutoff        0.5    [0,1]
  SFString [in,out] alphaMode          "AUTO" ["AUTO", "OPAQUE", "MASK", "BLEND"]
  SFNode   [in,out] backMaterial       NULL   [X3DOneSidedMaterialNode]
  SFNode   [in,out] fillProperties     NULL   [FillProperties]
  SFNode   [in,out] lineProperties     NULL   [LineProperties]
  SFNode   [in,out] material           NULL   [X3DMaterialNode]
  SFNode   [in,out] metadata           NULL   [X3DMetadataObject]
  SFNode   [in,out] pointProperties    NULL   [PointProperties]
  MFNode   [in,out] shaders            []     [X3DShaderNode]
  SFNode   [in,out] texture            NULL   [X3DTextureNode]
  SFNode   [in,out] textureTransform   NULL   [X3DTextureTransformNode]
}

The Appearance node specifies the visual properties of geometry. The value for each of the fields in this node may be NULL. However, if the field is non-NULL, it shall contain one node of the appropriate type.

The acousticProperties field, if specified, shall contain an AcousticProperties node describing coefficients related to the physical propagation of sound for various materials.

The alphaCutoff field provides a threshold value for pixel rendering as either transparent or opaque, used either when alphaMode has value MASK or else when alphaMode has value AUTO and the browser determines that MASK mode is most appropriate for use.

The alphaMode field determines how the final transparency value is computed for each pixel. The final alpha value is determined by various properties of the material and textures (following the lighting model equations given in the 17 Lighting component) or by custom shaders, when these are used (see 31 Programmable shaders component). The following values of alphaMode are allowed:

The backMaterial field, if specified, shall contain a Material, PhysicalMaterial or UnlitMaterial node. It is only allowed to define a backMaterial if the material is also defined (not NULL). The node type provided to backMaterial (if any) must match the node type provided to material. This field allows to render back faces with a different material parameters than the front faces. The meaning and all constraints of this field are explained in the section Two-sided materials.

The fillProperties field, if specified, shall contain a FillProperties node. If fillProperties is NULL or unspecified, the fillProperties field has no effect.

The lineProperties field, if specified, shall contain a LineProperties node. If lineProperties is NULL or unspecified, the lineProperties field has no effect.

The material field, if specified, shall contain a Material, PhysicalMaterial, TwoSidedMaterial (deprecated) or UnlitMaterial node. If the material field is NULL or unspecified, lighting is off (all lights are ignored during rendering of the object that references this Appearance) and the unlit object colour is (1, 1, 1). Details of the X3D lighting model are in 17 Lighting component.

The pointProperties field, if specified, shall contain a PointProperties node. If pointProperties is NULL or unspecified, the pointProperties field has no effect.

The shaders field contains a listing, in order of preference, of nodes that describe programmable shaders that replace the fixed rendering requirements of this part of ISO/IEC 19775 with user-provided functionality. If the field is not empty, one shader node is selected and the fixed rendering requirements defined by this specification are ignored. The field shall contain one of the various types of shader nodes as specified in 31 Programmable shaders component.

The texture field, if specified, shall contain one of the various types of texture nodes (see 18 Texturing component). If the texture node is NULL or the texture field is unspecified, the object that references this Appearance is not textured.

The textureTransform field, if specified, shall contain a TextureTransform node as defined in 18.4.8 TextureTransform. If the textureTransform is NULL or unspecified, the textureTransform field has no effect.

12.4.3 FillProperties

FillProperties : X3DAppearanceChildNode { 
  SFBool  [in,out] filled     TRUE
  SFColor [in,out] hatchColor 1 1 1 [0,1]
  SFBool  [in,out] hatched    TRUE
  SFInt32 [in,out] hatchStyle 1     [0,∞)
  SFNode  [in,out] metadata   NULL  [X3DMetadataObject]
}

The FillProperties node specifies additional properties to be applied to all polygonal areas on top of whatever appearance is specified by the other fields of the respective Appearance node. Thus, hatches are applied on top of the already rendered appearance of the node. Thus, if filled is TRUE, the polygonal area is filled according to the other fields of the Appearance node. If hatched is TRUE, the polygonal area is hatched as specified by the hatchStyle field. Hatches shall be applied after fills are applied.

The hatchStyle field selects a hatch pattern as defined in the International Register of Graphical Items (see [REG]). The hatches are rendered using the colour specified by the hatchColor field. Browsers shall support hatchstyles 1-6 with hatchstyle 1 being the default. X3D browsers may support any other of the registered hatchstyles. If a hatchstyle that is not supported is requested, hatchstyle 1 shall be used. Table 12.2 specifies the first nineteen hatch styles as defined in the Hatchstyle Section of the International Register of Items. Examples of each hatch style are available at the International Register of Items.

Table 12.2 — International register of items hatchstyles

1 Horizontal equally spaced parallel lines
2 Vertical equally spaced parallel lines
3 Positive slope equally spaced parallel lines
4 Negative slope equally spaced parallel lines
5 Horizontal/vertical crosshatch
6 Positive slope/negative slope crosshatch
7 (cast iron or malleable iron and general use for all materials)
8 (steel)
9 (bronze, brass, copper, and compositions)
10 (white metal, zinc, lead, babbit, and alloys)
11 (magnesium, aluminum, and aluminum alloys)
12 (rubber, plastic, and electrical insulation)
13 (cork,felt, fabric, leather, and fibre)
14 (thermal insulation)
15 (titanium and refractory material)
16 (marble, slate, porcelain, glass, etc.)
17 (earth)
18 (sand)
19 (repeating dot)

The associated geometry shall be filled and/or hatched only when the respective values of the filled and/or hatched fields have value TRUE.

12.4.4 LineProperties

LineProperties : X3DAppearanceChildNode { 
  SFBool  [in,out] applied              TRUE
  SFInt32 [in,out] linetype             1    [1,∞)
  SFFloat [in,out] linewidthScaleFactor 0    (-∞,∞)
  SFNode  [in,out] metadata             NULL [X3DMetadataObject]
}

The LineProperties node specifies additional properties to be applied to all line geometry. The linetype and linewidthScaleFactor fields shall only be applied when the applied field has value TRUE. When the value of the applied field is FALSE, a solid line of nominal width shall be produced. The colour of the line is specified by the associated Material node or X3DColorNode color values.

The linetype field selects a line pattern as defined in the International Register of Graphical Items (see [REG]). X3D browsers shall support linetype values 1 through 5, with 1 being the default value. X3D browsers may support any other of the registered linetype values. If a linetype that is not supported is requested, value 1 shall be used. Table 12.2 specifies the first sixteen linetype values as defined in the Linetype Section of the International Register of Items.

Table 12.3 — International register of items linetypes

1 Solid
2 Dashed
3 Dotted
4 Dashed-dotted
5 Dash-dot-dot
6 (single arrow)
7 (single dot)
8 (double arrow)
10 (chain line)
11 (center line)
12 (hidden line)
13 (phantom line)
14 (break line 1)
15 (break line 2)
16 User-specified dash pattern

The arrowhead is drawn as short lines forming barbs at any convenient angle between 15 and 90 degrees. The arrowhead is closed and filled in. For linetype "single arrow", the arrowhead is rendered so that the arrow tip occurs at the last point of the each individual list of points passed to a polyline and is in the direction of the last vector. For linetype "double arrow", the first arrowhead is rendered so that the arrow tip occurs at the first point of the list of points passed to a polyline and is in the reverse direction of the first vector. The second arrowhead is rendered as for "single arrow" at the opposite end of the polyline.

The linewidthScaleFactor field is a multiplicative value that scales a browser-dependent nominal line width by the given value. This resulting value shall then be mapped to the nearest available line width. A value less than or equal to zero refers to the minimum available line width.

12.4.5 Material

Material : X3DOneSidedMaterialNode {
  SFFloat  [in,out] ambientIntensity          0.2          [0,1]
  SFNode   [in,out] ambientTexture            NULL         [X3DSingleTextureNode]
  SFString [in,out] ambientTextureMapping     ""

  SFColor  [in,out] diffuseColor              0.8 0.8 0.8  [0,1]
  SFNode   [in,out] diffuseTexture            NULL         [X3DSingleTextureNode]
  SFString [in,out] diffuseTextureMapping     ""

  SFColor  [in,out] emissiveColor             0 0 0        [0,1]
  SFNode   [in,out] emissiveTexture           NULL         [X3DSingleTextureNode]
  SFString [in,out] emissiveTextureMapping    ""

  SFNode   [in,out] metadata                  NULL         [X3DMetadataObject]

  SFFloat  [in,out] normalScale               1            [0, ∞)
  SFNode   [in,out] normalTexture             NULL         [X3DSingleTextureNode]
  SFString [in,out] normalTextureMapping      ""

  SFFloat  [in,out] occlusionStrength         1            [0,1]
  SFNode   [in,out] occlusionTexture          NULL         [X3DSingleTextureNode]
  SFString [in,out] occlusionTextureMapping   ""
  
  SFFloat  [in,out] shininess                 0.2          [0,1]
  SFNode   [in,out] shininessTexture          NULL         [X3DSingleTextureNode]
  SFString [in,out] shininessTextureMapping   ""

  SFColor  [in,out] specularColor             0 0 0        [0,1]
  SFNode   [in,out] specularTexture           NULL         [X3DSingleTextureNode]
  SFString [in,out] specularTextureMapping    ""

  SFFloat  [in,out] transparency              0            [0,1]
}

The Material node specifies surface material properties for associated geometry nodes. It indicates that a surface is using Phong lighting model. 17 Lighting component contains a detailed description of the X3D lighting model equations.

The material parameters are specified as scalars or RGB colors in the X3D file. All of the SFFloat and SFColor fields in the Material node range from 0.0 to 1.0.

Moreover every material parameter can be adjusted using a texture. This allows to vary this parameter across the surface. The information sampled from the texture is always multiplied by the simple scalar/color fields.

Examples of texture usage:

The fields in the Material node determine how light reflects off an object to create color:

  1. The ambientIntensity and ambientTexture fields specify how much ambient light from light sources this surface shall reflect. Ambient light is omnidirectional and depends only on the number of light sources, not their positions with respect to the surface.

    Ambient parameter is calculated as ambientIntensity × diffuseColor × textureSample(ambientTexture).rgb.

  2. The diffuseColor and diffuseTexture fields reflect all X3D light sources depending on the angle of the surface with respect to the light source. The more directly the surface faces the light, the more diffuse light reflects.
  3. The emissiveColor and emissiveTexture fields model "glowing" or "unlit" objects. See X3DOneSidedMaterialNode for the description of these fields.
  4. The specularColor, specularTexture, shininess and shininessTexture fields determine the specular highlights ( e.g., the shiny spots on an apple).

    When the angle from the light to the surface is close to the angle from the surface to the viewer, the specularColor ×  textureSample(specularTexture).rgb is added to the diffuse and ambient color calculations.

    Lower shininess values produce soft glows, while higher values result in sharper, smaller highlights. Shininess is calculated as shininess ×  textureSample(shininessTexture).a.

  5. The transparency field (together with alpha channel of the diffuseTexture) specifies how "clear" an object is, with 1.0 being completely transparent, and 0.0 completely opaque.

    The transparency determines the opacity as opacity = 1.0 - transparency. This is then multiplied by the alpha channel of diffuseTexture to determine the final alpha of the rendered pixel.

The RGB channels of diffuseTexture, specularTexture and emissiveTexture are multiplied by the corresponding diffuseColor, specularColor, emissiveColor before being used in the current lighting calculation. The alpha channel of a diffuseTexture is multiplied by the material opacity (which equals just 1.0 - transparency). The alpha channels contents of specularTexture and emissiveTexture are ignored.

The shininessTexture alpha channel contains values multiplied with the shininess factor of the Material node. The RGB channels contents of the shininessTexture are ignored.

It is expected, and advised, that authors reuse the same texture node for specularTexture and shininessTexture. The specular data is deliberately contained in different channels (RGB) than the shininess data (Alpha).

The optional occlusionTexture can be used to indicate areas of indirect lighting, typically called ambient occlusion. Only the Red channel of the texture is used for the computation, the other channels are ignored. Higher values indicate areas that should receive full indirect lighting and lower values indicate no indirect lighting. The occlusionStrength determines how much does the occlusion texture affect the final result.

See the section 12.2.4 Texture mapping specified in material nodes for a description how the texture coordinates and texture coordinate transformations are determined based on the xxxTextureMapping fields of this node.

12.4.6 PhysicalMaterial

PhysicalMaterial : X3DOneSidedMaterialNode {
  SFColor  [in,out] baseColor                       1 1 1  [0,1]
  SFNode   [in,out] baseTexture                     NULL   [X3DSingleTextureNode]
  SFString [in,out] baseTextureMapping              ""

  SFColor  [in,out] emissiveColor                   0 0 0  [0,1]
  SFNode   [in,out] emissiveTexture                 NULL   [X3DSingleTextureNode]
  SFString [in,out] emissiveTextureMapping          "" 
  
  SFNode   [in,out] metadata                        NULL   [X3DMetadataObject]

  SFFloat  [in,out] metallic                        1      [0,1]
  SFNode   [in,out] metallicRoughnessTexture        NULL   [X3DSingleTextureNode]
  SFString [in,out] metallicRoughnessTextureMapping ""

  SFFloat  [in,out] normalScale                     1      [0, ∞)
  SFNode   [in,out] normalTexture                   NULL   [X3DSingleTextureNode]
  SFString [in,out] normalTextureMapping            ""

  SFFloat  [in,out] occlusionStrength               1      [0,1]
  SFNode   [in,out] occlusionTexture                NULL   [X3DSingleTextureNode]
  SFString [in,out] occlusionTextureMapping         ""

  SFFloat  [in,out] roughness                       1      [0,1]

  SFFloat  [in,out] transparency                    0      [0,1]
}

The PhysicalMaterial node specifies surface material properties for associated geometry nodes. It indicates that a physical lighting model should be used for the computation. 17 Lighting component contains a detailed description of the X3D lighting model equations.

Physical interpretation of the material parameters follows. These parameter descriptions closely follow the glTF specification (see [glTF]).

NOTE  The physical material properties of X3D are also deliberately consistent with the glTF 2.0 material definition. Effectively, converting (in either direction) between X3D PhysicalMaterial and glTF 2.0 material definitions is equivalent.

The physical lighting equation, as an input, relies on the following parameters:

When calculating metallicParameter and roughnessParameter terms, the Red and Alpha channels of the metallicRoughnessTexture are ignored. It is possible to use the same texture for metallicRoughnessTexture and occlusionTexture, as they deliberately look at different channels, so all the information can be contained in one RGB texture.

The final alpha, used for blending or alpha-testing, is calculated as baseTexture alpha channel multiplied with the opacity (1.0 - transparency). This is consistent with the behavior of diffuseColor, diffuseTexture and transparency on the Phong Material. If the baseTexture was not specified, it is also possible to use the Application.texture. See the 17.2.2.6 Physical lighting model for the exact specification, and the 12.2.5 Coexistence of textures specified in material nodes with the "Appearance.texture" field for a description how Appearance.texture is used.

Moreover the PhysicalMaterial defines the emissiveColor and optional emissiveTexture. The resulting emissiveParameter term is simply added to the pixel color, this behavior is consistent for all X3D materials.

The optional occlusionTexture can be used to indicate areas of indirect lighting, typically called ambient occlusion. Only the Red channel of the texture is used for the computation, the other channels are ignored. Higher values indicate areas that should receive full indirect lighting and lower values indicate no indirect lighting. The occlusionStrength determines how much does the occlusion texture affect the final result.

The baseParameter color has two different interpretations depending on the value of metallicParameter. When the material is a metal, the baseParameter color is the specific measured reflectance value at normal incidence (F0). For a non-metal the baseParameter color represents the reflected diffuse color of the material. In this model it is not possible to specify a F0 value for non-metals, and a linear value of 4% (0.04) is used.

The following equations show how to calculate bidirectional reflectance distribution function (BRDF) inputs ( cdiff, F0, ) from the metallic-roughness material properties.

const dielectricSpecular = rgb(0.04, 0.04, 0.04)
const black = rgb(0, 0, 0)
cdiff = lerp(baseParameter * (1 - dielectricSpecular.r), black, metallicParameter)
F0 = lerp(dieletricSpecular, baseParameter, metallicParameter)
"α

         = roughnessParameter ^ 2

See the section 12.2.4 Texture mapping specified in material nodes for a description how the texture coordinates and texture coordinate transformations are determined based on the xxxTextureMapping fields of this node.

12.4.7 PointProperties

PointProperties : X3DAppearanceChildNode {
  SFFloat  [in,out] pointSizeScaleFactor  1 [1,∞)
  SFFloat  [in,out] pointSizeMinValue     1 [0,∞)
  SFFloat  [in,out] pointSizeMaxValue     1 [0,∞)
  SFVec3f  [in,out] attenuation           1 0 0 [0,∞)

  SFNode   [in,out] metadata              NULL [X3DMetadataObject]
}

The PointProperties node specifies additional properties to be applied to all point geometry. The colour of the line is specified by the associated Material node or X3DColorNode color values.

pointSizeScaleFactor is a value determining the nominal point size before modification by the sizing modifications, as determined by the pointSizeMinValue, pointSizeMaxValue, and attenuation values discussed below. The nominal rendered point size is a browser-dependent minimum renderable point size.

pointSizeMinValue is minimum allowed scaling factor on nominal browser point scaling. pointSizeMaxValue is maximum allowed scaling factor on nominal browser point scaling. The provided value for pointSizeMinValue must be less than or equal to value for pointSizeMaxValue.

The attenuation field defines a depth perception effect in a point cloud rendering by making points close to the viewer appear larger. The modification of point size depending on distance from the view occurs in two steps, starting with the nominal point size as determined by the pointSizeScaleFactor field. The attenuation field defines three parameters a, b, and c from the components of a single SFVec3f value:

a = attenuation[0]
b = attenuation[1]
c = attenuation[2]

Together these parameters define an attenuation factor 1/(a + b×r + c×r2) where r is the distance from the observer position (current viewpoint) to each point. The nominal point size is multiplied by the attenuation factor and then clipped to a minimum value of pointSizeMinValue × the minimum renderable point size, then clipped to a maximum size of pointSizeMaxValue × minimum renderable point size.

When a X3DTextureNode is defined in the same Appearance instance as PointProperties node, the points of a PointSet shall be displayed as point sprites using the given texture(s).

TODO reference/bibliography International register of items for markertype.

12.4.8 Shape

Shape : X3DShapeNode {
  SFNode  [in,out] appearance  NULL     [X3DAppearanceNode]
  SFBool  [in,out] bboxDisplay FALSE
  SFBool  [in,out] castShadow  TRUE
  SFNode  [in,out] geometry    NULL     [X3DGeometryNode]
  SFNode  [in,out] metadata    NULL     [X3DMetadataObject]
  SFBool  [in,out] visible     TRUE
  SFVec3f []       bboxCenter  0 0 0    (-∞,∞)
  SFVec3f []       bboxSize    -1 -1 -1 [0,∞) or −1 −1 −1
}

The Shape node has two fields, appearance and geometry, that are used to create rendered objects in the world. The appearance field contains an Appearance node that specifies the visual attributes ( e.g., material and texture) to be applied to the geometry. The geometry field contains a geometry node. The specified geometry node is rendered with the specified appearance nodes applied. See 12.2 Concepts for more information.

17 Lighting component contains details of the X3D lighting model and the interaction between Appearance nodes and geometry nodes.

If the geometry field is NULL, the object is not drawn.

The bboxCenter and bboxSize fields specify a bounding box that encloses the Shape node's geometry. This is a hint that may be used for optimization purposes. The results are undefined if the specified bounding box is smaller than the actual bounding box of the geometry at any time. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and, if needed, is calculated by the browser. A description of the bboxCenter and bboxSize fields is contained in 10.2.2 Bounding boxes.

12.4.9 TwoSidedMaterial (deprecated)

TwoSidedMaterial : X3DMaterialNode {
  SFFloat [in,out] ambientIntensity     0.2         [0,1]
  SFFloat [in,out] backAmbientIntensity 0.2         [0,1]
  SFColor [in,out] backDiffuseColor     0.8 0.8 0.8 [0,1]
  SFColor [in,out] backEmissiveColor    0 0 0       [0,1]
  SFFloat [in,out] backShininess        0.2         [0,1]
  SFColor [in,out] backSpecularColor    0 0 0       [0,1]
  SFFloat [in,out] backTransparency     0           [0,1]
  SFColor [in,out] diffuseColor         0.8 0.8 0.8 [0,1]
  SFColor [in,out] emissiveColor        0 0 0       [0,1]
  SFNode  [in,out] metadata             NULL        [X3DMetadataObject]
  SFFloat [in,out] shininess            0.2         [0,1]
  SFBool  [in,out] separateBackColor    FALSE
  SFColor [in,out] specularColor        0 0 0       [0,1]
  SFFloat [in,out] transparency         0           [0,1]
}

NOTE  this node is deprecated since X3D version 4.0. Future versions of the standard may remove this node. The upgrade path is as follows:

This node defines material properties that can effect both the front and back side of a polygon individually. These materials are used for both the front and back side of the geometry whenever the X3D lighting model is active.

If the separateBackColor field is set to TRUE, the rendering shall render the front and back faces of the geometry with different values. If the value is FALSE, the front colours are used for both the front and back side of the polygon, as per the existing X3D lighting rules.

When calculating the terms in the lighting equations, the front geometry shall use the fields ambientIntensity, diffuseColor, emissiveColor, shininess, specularColor, and transparency. The faces that are determined to be the back side are rendered using backAmbientIntensity, backDiffuseColor, backEmissiveColor, backShininess, and backTransparency as the appropriate components in the lighting equations.

12.4.10 UnlitMaterial

UnlitMaterial : X3DOneSidedMaterialNode {
  SFColor  [in,out] emissiveColor                   1 1 1  [0,1]
  SFNode   [in,out] emissiveTexture                 NULL   [X3DSingleTextureNode]
  SFString [in,out] emissiveTextureMapping          ""
  SFNode   [in,out] metadata                        NULL   [X3DMetadataObject]
  SFFloat  [in,out] normalScale                     1      [0, ∞)
  SFNode   [in,out] normalTexture                   NULL   [X3DSingleTextureNode]
  SFString [in,out] normalTextureMapping            ""
  SFFloat  [in,out] transparency                    0      [0,1]
}

Material that is unaffected by light sources. Suitable to create various non-realistic effects, when the colors are defined explicitly and are not affected by the placement of the shape relative to the lights or camera.

The output color and opacity, called emissiveParameter by the lighting equations, are determined like this:

  1. Use the emissiveColor field value as the emissiveParameter.rgb. Use the 1.0 - transparency as the emissiveParameter.a.
  2. If shape is using Color node then the information from Color node overrides the emissiveParameter.rgb. If shape is using ColorRGBA node then the information from ColorRGBA overrides both the emissiveParameter.rgb and the emissiveParameter.a.

    NOTE  This is consistent with how Color or ColorRGBA override diffuseColor and transparency in case of Material.

  3. If the emissiveTexture is not NULL, then it multiplies (component-wise) the emissiveParameter.rgb (multiplied by the texture RGB channels) and emissiveParameter.a (multiplied by the texture alpha channel).

    If the emissiveTexture is NULL, but Appearance.texture field is not NULL, then the same logic is applied to the Appearance.texture texture: it multiplies emissiveParameter.rgb and emissiveParameter.a. See 12.2.5 Coexistence of textures specified in material nodes with the "Appearance.texture" field for a description how is the Appearance.texture field used.

Note about default values: This node inherits the emissiveColor field from the X3DOneSidedMaterialNode ancestor, but the default value of this field changes: only for UnlitMaterial, the default emissiveColor is 1 1 1 (white), instead of 0 0 0 (black, default of X3DOneSidedMaterialNode.emissiveColor).

Implementation hint: Normal vectors information is not useful for the calculation of unlit material. Implementations can ignore the normal vectors provided in the geometry node (per-face or per-vertex) and in the normalTexture field. Implementations are encouraged to optimize this case, and not send unneeded normals data to GPU, and not calculate implicit normal vectors (normally derived from creaseAngle and ccw fields). However, there is an exception to this optimization: if the shape is using TextureCoordinateGenerator with some modes (CAMERASPACENORMAL, CAMERASPACEREFLECTIONVECTOR) then the shader code may need access to normals anyway.

See the section 12.2.4 Texture mapping specified in material nodes for a description how the texture coordinates and texture coordinate transformations are determined based on the xxxTextureMapping fields of this node.

cube 12.5 Support levels

The Shape component provides three levels of support as specified in Table 12.4.

Table 12.4 — Shape component support levels

Level Prerequisites Nodes/Features Support
1 Core 1
Rendering 1
Texturing 1
X3DAppearanceChildNode(abstract) n/a
X3DAppearanceNode (abstract) n/a
  X3DMaterialNode (abstract) n/a
  X3DOneSidedMaterialNode (abstract) n/a
X3DShapeNode (abstract) n/a
Appearance Optional support for textureTransform, lineProperties, fillProperties, shaders, backMaterial.
Material Support for diffuseTexture required. Optional support for ambientIntensity, shininess, specularColor, ambientTexture, emissiveTexture, normalTexture, occlusionTexture, shininessTexture, specularTexture).
UnlitMaterial All fields fully supported.
Shape All fields fully supported.
2 Core 1
Lighting 4
Rendering 1
Texturing 1
All Level 1 nodes except Appearance All fields fully supported.
    Appearance Optional support for the same properties as on level 1.
    LineProperties All fields fully supported.
PhysicalMaterial All fields fully supported.
3 Core 1
Lighting 4
Rendering 1
Texturing 1
 
All Level 2 nodes except Appearance All fields fully supported.
    Appearance Optional support for backMaterial.
    FillProperties All fields fully supported.
    PointProperties All fields fully supported.
    TwoSidedMaterial (deprecated) Support optional.
4 Core 1
Lighting 4
Grouping 1
Rendering 1
All Level 3 nodes All fields fully supported.
    AcousticProperties All fields fully supported.
--- X3D separator bar ---