Loading non-square textures, from a 256x256 spritesheet in lwjgl(JAVA)

Question

so I'm doing lwjgl, so far I have the loading of 16x16 textures from a 256x256 spritesheet all working, using this code to get the location of the textures:

 public  Vector2f[] calculateUVMapping(int texture, int atlasWidth, int atlasHeight) {
    int textureIndex = texture;

    int u = textureIndex % atlasWidth;
    int v = textureIndex / atlasHeight;

    float xOffset = 1f / atlasWidth;
    float yOffset = 1f / atlasHeight;

    float uOffset = (u * xOffset);
    float vOffset = (v * yOffset);

    Vector2f[] UVList = new Vector2f[4];

    UVList[0] = new Vector2f(uOffset, vOffset); // 0,0
    UVList[1] = new Vector2f(uOffset, vOffset + yOffset); // 0,1
    UVList[2] = new Vector2f(uOffset + xOffset, vOffset + yOffset); // 1,1
    UVList[3] = new Vector2f(uOffset + xOffset, vOffset); // 1,0


    return UVList;
}

This takes the texture ID from left to right, top to bottom in the atlas, starting from 0 and the amount of textures the atlas holds, so to get the first texture in a 256x256 sheet (holds 16 textures in each row and column) I'd do calculateUVMapping(0,16,16), along with he corresponding endings for the vector and variable.

Now, say I want to have a 200x20 texture in another 256x256 sheet, or any nonsquare texture, actually, and I want to apply that to a quad- could this code work for getting the co-ords for it, or what code should I use for those?

Answer 1

Simply calculate UVs (0,0 point is left bottom, 1,1 point is right top) assuming you v got sprite texture dimensions sp in pixels just divide it by texture size:

SpriteDimensions sp; //that you must know

Vector2f[] UVList = new Vector2f[4];

UVList[0] = new Vector2f(sp.x / tex_width, sp.y / tex_height); // 0,0
UVList[1] = new Vector2f(sp.x / tex_width, (sp.y + sp.height) / tex_height); // 0,1
UVList[2] = new Vector2f((sp.x + sp.width) / tex_width, (sp.y + sp.height) / tex_height); // 1,1
UVList[3] = new Vector2f((sp.x + sp.width) / tex_width, sp.y / tex_height); // 1,0