I am currently reviewing the support for transparent materials that I put into the OpenSceneGraph Collada plugin about a year ago. I realise that I need to do some more work on it to make alpha blended texture maps work. I have some questions I need answering if possible. So here goes.
1. Am I correct in assuming that the default for the opaque attribute of the transparent element at version 1.4.1 is A_ONE (an alpha value of 1 is opaque) and at the 1.5.1 the default has changed to A_ZERO (an alpha value of 0 is opaque)?
2. YOU CAN IGNORE THIS QUESTION FOR THE TIME BEING, I NEED TO REPHRASE IT!!!! I was assuming that the colour referred to in the specification of the transparent element was the colour supplied by that element. But some implementations(e.g. Sketchup) do not seem to produce Collada documents that agree with that. Can someone confirm the source of the colour in the following circumstances.
i. The transparent element present and specifiying a colour and no other colours or texture elements present.
ii. The transparent element present and specifiying a colour, but with, for instance a diffuse colour or texture element also present.
iii. The transparent element present and specifiying a texture and no other colours or texture elements present.
iv. The transparent element present and specifiying a texture, but with, for instance a diffuse colour or texture element also present.
v. The transparent element not present, but the transparency element present and say, a diffuse colour element present.
3. Other posts in this forum say that in a situation where both a diffuse texture and a transparent texture are present some sort of multitexturing should be performed. But taking the phong technique as an example no specification of how this should be performed is given. The phong equation given in the specification does not have a term for the refracted colour. Can any one give me any hints how this should be done in OpenGL terms.