XNA texture coordinates on merged textures
I got a problem with texture coordinates. First I would like to describe what I want to do then I will ask the question.
I want to have a mesh that has more textures using only one big texture. The big texture merges all textures the mesh is using in it. I made a routine that merges textures, that is no problem, but I still have to modify the texture coordinates, so the mesh that now uses only one texture instead of many has everything placed well.
See the picture:
On the upper left corner I got one of the textures (let's call it A) I merged into a big texture, the right one (B). A's top left is 0,0 and bottom right is 1,1. For easy use let's say that B.width = A.width * 2 and so for the height too. So on B the mini texture (M what is the A originally) bottom-right should be 0.5,0.5.
I got no problems understanding these so far and I hope I understood it ok. But the problem here is, that there are texture coordinates that are:
- above 1
- negative
on the original A. What should these be on M?
Let's say, A has -0.1,0 - is that -0.05,0 on M inside B?
What about those numbers that are outside 0..1 region? Is -3.2,0 on A -1.6 or -3.1 on B? So I clip of the part that is %1 and divide by 2 (because I stated above that width is double) or should I divide the whole number by 2? As far I understand so far, numbers outside this region are about mirroring the texture. How do I manage this, so the output does not contain the orange texture from B?
If my question is not clear enough (I am not much skilled in English), please ask and I will edit/answer, just help me clear my confusion :)
Thanks in advance: Péter
A single texture has coordinates in [0-1,0-1] range
The new texture has coordinates in [0-1,0-1] range
In your new texture composed by four single textures, your algoritm has to translate texture coordinates this way.
- Blue single square texture will have new coordinates in [0-0.5, 0-0.5] range
- Orange single square texture will have new coordinates in [0.5-1, 0-0.5] range