Changeset 9906

03/11/09 14:27:51 (5 years ago)

From Neil Hughes, "I've spent the past four days playing with PNG files on 3DS objects, and I think I may have come across a small issue with the 3DS loader.

At the company where I work we model literally thousands of 3DS models for all types of objects. Most don't have transparent textures applied to them, but a few do. The issue is that a texture may have an alpha channel defined, yet its 3DS material definition is not marked as being an alpha source, or transparent. This can happen for any number of modelling reasons (so I'm told) but the net effect is that when a 3DS object is loaded with such a material applied, the stateset creation for the 3DS geometry omits to add the GL_BLEND attribute as neither of the conditions that it currently tests for are satisfied under this scenario.

However, one thing that is apparently an indication of transparency/alpha information that we do make use of when modelling, but that the 3DS reader omits to test, is that we assign to the transparent texture to the opacity_map of the 3DS material structure.

Now, having discussed with our modellers the theory behind the opacity map, it seems that it is safe to say that if an opacity map is specified, then the reader should really apply the GL_BLEND attribute as it is an indication of some form of blending being required between materials.

With this in mind, I have made a minor change to the function createStateSet below, from the ReaderWriter?3DS.cpp file, that checks for an opacity map having been specified, and in such a scenario the GL_BLEND attribute is applied to the geometry. This fixed our issue, and thought it might be helpful to others."

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