Extrusions along x/z axes look flat

[sevaa]

X3D Extrusion elements where the spine is straight along the X or Z direction appear flat in X3DOM. In general, if the straight spine is not aligned with the Y axis, X3DOM distorts the cross-section.

See here: http://www.jishop.com/temp/x3d/ , click on Extrusions, notice how the topmost two ones look flat.

The spec says: "If the entire spine is collinear, the SCP is computed by finding the rotation of a vector along the positive Y-axis (v1) to the vector formed by the spine points (v2). The Y=0 plane is then rotated by this value."

Here's how I think it should be interpreted: find the rotation between the Y axis and the spine direction, and then apply that rotation to the vector (0, 0, 1) to get the Z axis for the cross-section plane (CSP). As a result, if the spine is along the X axis, the rotation is pi/2 clockwise around the Z axis, so the Z of CSP should be (0,0,1). If the spine is along the Z axis, the rotation is pi/2 counterclockwise around the X axis, and the Z of the CSP is (0, -1, 0).

[splace]

confirmed as fault.

i think you can write a lot more clearly a part of the spec. as; "extrusion cross-sections, for straight splines, with no orientations, are at right-angle to the spline." a simple and useful situation.

the definition also tells you how to rotate the csp, which is with x will be up, +y.

however the spec. seems to neglect the situation of the spine going -y, where the rotation of the scp seems to be undefined.

this has been recorded here:- http://www.web3d.org/wiki/index.php/Extrusion_Edge_Cases