Can anyone help me understand these texture coordinates?

[Addictman]

Hi.

Imagine a very basic Texture atlas, looking roughly like this: (A and B are the 2 different pieces).

AAB
AA

Now, judging from this, piece A can be found at

1	[ left: 0.0f, bottom: 0.0f, right: 0.66667f, top: 1.0f ]

I have always imagined, and was sure that piece B could be found at

1	[ left: 0.66667f, bottom: 0.5f, right: 1.0f, top: 1.0f ]

However, that's not coming out right at all. Piece B IS coming out right at

1	[ left: 0.66667f, bottom: 0.0f, right: 1.0f, top: 0.5f ]

however.

I render as triangles, and my data for rendering B looks like this:

Vertexbuffer

1   2   3   4   5   6

float[] {                        x - 64, y + 64, // top left             x - 64, y - 64, // bottom left             x + 64, y - 64, // bottom right                       x + 64, y + 64 // top right                  }

Texturebuffer (doesnt work, but what I thought was correct)

1   2   3   4   5   6

float[] {                        0.66667f, 1.0f,              0.66667f, 0.5f,              1.0f,0.5f,              1.0f,1.0f                    }

Texturebuffer (works, but what I thought was wrong)

1   2   3   4   5   6

float[] {                        0.66667f, 0.5f,              0.66667f, 0.0f,              1.0f,0.0f,              1.0f,0.5f                    }

I hope my question is understandable, and that someone can explain to me what's going on here.

[Addictman]

Ok, I should have tried this first of course, rendering the entire Atlas... The entire texture is flipped vertically, so that explains the weird texture coordinates.

[theagentd]

Ok, I should have tried this first of course, rendering the entire Atlas... The entire texture is flipped vertically, so that explains the weird texture coordinates.

I was just going to say that. xD