Examine mode behavior for exploring geospatial worlds
One of the issues raised at 2-day X3D Earth technical requirements workshop (http://www.web3d.org/x3d-earth/workshop2006/) was the need for some uniformity amongst browsers for effective user navigation in X3D Earth worlds. For MBARI's ROV Dive data visualization application (http://www.mbari.org/staff/mccann/vrml/ROVDataVis/papers/w3ds2004Paper-Rev4_submitted.pdf) we have found CosmoPlayer's Examine mode with Shift key set to Turbo Mode and Continuous Seek to be very effective and easy to use on a computer with a standard keyboard and mouse. The user needs to explore any part of the 3D world - key to enabling this capability are features in the browser that allow interactive changes to the point of rotation and movement about it with minimal keyboard and mouse operations. This is done with mouse action modification keys to:
- change the center of rotation location
- orbit about the selected point of rotation
- zoom toward and away from the point of rotation
Here are recommendations to browser developers for implementing the Examine mode to give these capabilities:
- Dragging the mouse left and right while holding the left mouse button down causes viewpoint rotation about a vertical axis that passes through the point of rotation. This vertical axis is always perpendicular to viewpoint vector. Left mouse motion rotates the viewpoint clockwise (as viewed from the top) about the vertical axis. Rotation is tied to the mouse motion - there is no damping or delay.
- Dragging the mouse up and down while holding the left mouse button down causes rotation about a horizontal axis that passes through the point of rotation. Up mouse motion rotates the viewpoint clockwise (as viewed from the right) about the horizontal axis. Rotation is tied to the mouse motion - there is no damping or delay.
- Holding the Ctrl key (or other key that may be user selectable) down modifies the left button down mouse drag movement such that up and down (Y-axis) movement causes the viewpoint to zoom toward and from the point of rotation. Left and right mouse motion while Ctrl is held down has no effect. Shift and Ctrl (or other keys that may be user selectable) held at the same time also enables zoom but disables TouchSensors.
- Holding the Alt key (or other key that may be user selectable) modifies the mouse movement such that mouse motion while the left mouse button is held down is translated into a pan of the viewpoint in a plane passing through the viewpoint perpendicular to the vector pointing to the point of rotation. Shift and Alt (or other keys that may be user selectable) held at the same time also enables pan but disables TouchSensors.
- The point of rotation can be set by holding the Shift key (or other key that may be user selectable) while pointing at an object and clicking the left mouse button. To provide feedback that the point has been selected the viewpoint shall zoom about 20 percent of the distance toward that point.
- If mouse pointer is positioned over a TouchSensor then the pointer icon shall change its appearance to indicate that a left mouse click will activate the TouchSensor.
- Holding the Shift key (or other key that may be user selectable) overrides any TouchSensor that the pointer may be over and forces the mouse to function as the viewpoint navigation tool: drag operations cause rotation, click operations cause center of rotation point selection.
Mike McCann, Monterey Bay, Aquarium Research Institute