C++ OpenGL Wrong Collada Texture Coordinates - c++

Question

I am parsing a Collada file for animations. I have it drawn and animated fine but the issue now is how to setup the texture coordinates. I feed it to OpenGL exactly how the collada dae file gives it to me but its mapped completely wrong. The coordinates are range from [0-1].
Do I have to rearrange it?
If I do then please explain to me on how to go about it. I tried using GL_LINEAR and GL_NEAREST but it doesn't solve the problem. Any ideas why?
The models that I am using is the AstroBoy that http://www.wazim.com/Collada_Tutorial_1.htm gives and the Amnesia Servant Grunt.

Answer 1

Based on how you said it turns out to be mapped completely wrong, I'm guessing you haven't taken into account the the texture index values. I had a similar problem as well (although with a difference model). Just like you can have an array of index values so that OpenGL knows which order to draw the verticies, so to does Collada assign UV index values (and normal index values), and, annoyingly, they are never in the same order. Take the following Collada sample for instance:
<source id="Box001-POSITION">
<float_array id="Box001-POSITION-array" count="1008">
-167.172180 -193.451920 11.675772
167.172180 -193.451920 11.675772 .....
....
....
<source id="Box001-Normal0">
<float_array id="Box001-Normal0-array" count="5976">
-0.000000 -0.025202 -0.999682
-0.000000 -0.025202 -0.999682 .....
....
....
<source id="Box001-UV0">
<float_array id="Box001-UV0-array" count="696">
0.000000 0.000000
1.000000 0.000000
0.000000 1.000000 .....
....
....
<triangles count="664" material="_13 - Default">
<input semantic="VERTEX" offset="0" source="#Box001-POSITION"/>
<input semantic="NORMAL" offset="1" source="#Box001-Normal0"/>
<input semantic="TEXCOORD" offset="2" set="0" source="#Box001-UV0"/>
<p> 169 0 171 170 1 172 171 2 173 171 3
173 168 4 170 169 5 171 173 6 175 174
7 176 175 8 177 175 9 177 172 10 174 173 11 175 108 ....
The first three sections indicate the values of the verticies/normals/texture-coords but the final section indicates the index of each value. Notice how the first vertex index is 169, but the first normal index is 0. In fact, the normal indicies are completely normal, they progress as "0..1..2..3" but the indicies for the verticies and textures are all over the place! You have to order your vertex and texture values in the way the Collada file spcifies.
The other way is to write a little program that parses the collada file and rearranges all your vertex, normal and UV values into the right order based on the index values. Then you can just feed your points straight into OpenGL no questions asked. It's up to you of course, which way you want to handle it.
(PS: If you can make a good parser for Collada files, then the 'interleaved-indexing' is actually quite handy, if not though, I find it an over-complication on Collada's part, but you can't really do anything about it.)

Answer 2

No, I advice you to read some basic knowledge of collada .
<triangles count="664" material="_13 - Default">
<input semantic="VERTEX" offset="0" source="#Box001-POSITION"/>
<input semantic="NORMAL" offset="1" source="#Box001-Normal0"/>
<input semantic="TEXCOORD" offset="2" set="0" source="#Box001-UV0"/>
<p> 169 0 171 170 1 172 171 2 173 171 3......
the 169 is the first point index of a triangles,the 0 is the first normal index ,and the 171 is the first texcoord index ,and so on .