The first strange behavior is that if I set the root-level stateset's rendering hint to TRANSPARENT_BIN, the translucent geometry becomes suddenly opaque as its nominal location moves such that its viewing volume z-coordinate lies behind that of the map. At various locations the translucent geometry also occludes the GL points and lines without becoming opaque with respect to the map. If the rendering hint is set to OPAQUE_BIN, this does not happen and the scene renders with correct blending. Is this expected?
The second strange behavior is that the textured quad markers are completely occluded by the transparent geometry, which is instead rendered with a blend of the geometry's color and that of the map lying behind the marker. The marker texture image is in .bmp format and has no alpha channel, but the quad it is attached to has color ( 1, 1, 1, 1 ), and the OpenGL documentation indicates that when GL_REPLACE is in effect the geometry alpha is used where the texture does not supply an alpha value. I can't tell if this behavior is caused by odd texture behavior, or by some strange interaction of the AutoTransform with blending, or by something else entirely. I would greatly appreciate any suggestions.
- Ian Zeilstra
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