Virtual Reality Toolbox

VRML Coordinate System

VRML uses the right-handed Cartesian coordinate system. If your thumb, index finger, and middle finger of the right hand are held so that they form three right angles, then your thumb symbolizes the x-axis, your index finger the y-axis (pointing up), and your middle finger the z-axis.

The VRML coordinate system is different from the MATLAB, Aerospace Blockset, and SimMechanics coordinate systems. VRML uses the world coordinate system in which the y-axis points upward and the z-axis places objects nearer or farther from the front of the screen. It is important to realize this fact in situations involving the interaction of these different coordinate systems.

Rotation angles -- In VRML, rotation angles are defined using the right-hand rule. Imagine your right hand holding an axis while your thumb points in the direction of the axis towards its positive end. Your four remaining fingers point in a counter-clockwise direction. This counter-clockwise direction is the positive rotation angle of an object moving around that axis.

Child objects -- In the hierarchical structure of a VRML file, the position and orientation of child objects are specified relative to the parent object. The parent object has its local coordinate space defined by its own position and orientation. Moving the parent object also moves the child objects relative to the parent object.

Measurement units -- All lengths and distances are measured in meters, and all angles are measured in radians.

VRML History

VRML File Format