TextureAtlas

Overview

A fixed-grid texture atlas that stitches multiple same-sized tile images into a single GPU texture, minimizing texture-binding overhead at render time.

Layout:
Tiles are arranged in a square grid of gridSize x gridSize cells, numbered left-to-right, top-to-bottom, starting at index 0.

┌───┬───┬───┬───┐
│ 0 │ 1 │ 2 │ 3 │  row 0
├───┼───┼───┼───┤
│ 4 │ 5 │ 6 │ 7 │  row 1  (gridSize = 4)
└───┴───┴───┴───┘

UV Coordinates:
Call #getUVMin(int) and #getUVMax(int) to get the bottom-left and top-right UV corners for a tile.

These can be assigned directly to the four vertices of a quad.

TextureAtlas()

public TextureAtlas(String[] resourcePaths, int tileSize, int gridSize) {}

Builds a texture atlas by loading each image at the given classpath paths, copying their pixel data into a single CPU-side buffer, then uploading the whole atlas to the GPU as a single texture.

All source images must be exactly tileSize x tileSize pixels.

If fewer paths are provided than gridSize x gridSize, the remaining cells are left transparent.

copyTileIntoAtlas(...)

private void copyTileIntoAtlas(ByteBuffer atlasData, String resourcePath, int tileIndex) {}

Loads a single tile image and copies its pixel data into the correct region of the atlas buffer.

Getters and Setters

getUVMin(int tileIndex)

public Vector2f getUVMin(int tileIndex) {}

Returns the bottom-left UV coordinate of the tile at the given index.

Assign to the bottom-left vertex of the quad that should show this tile.

getUVMax(int tileIndex)

public Vector2f getUVMax(int tileIndex) {}

Returns the top-right UV coordinate of the tile at the given index.

Assign to the top-right vertex of the quad that should show this tile.

getUVs(int tileIndex)

public Vector2f[] getUVs(int tileIndex) {}

Returns all four UV coordinates for the tile at the given index, in order:

• Bottom-left
• Bottom-right
• Top-right
• Top-left

Convenient for directly populating the four vertices of a quad.

bind(int unit)

public void bind(int unit) {}

Binds the atlas texture to the specified unit.

unbind()

public void unbind() {}

Unbinds any texture from GL_TEXTURE_2D on the active unit.

destroy()

public void destroy() {}

Deletes the GPU texture. Call when the atlas is no longer needed.

getTextureID()

public int getTextureID() { return textureID; }

Returns the OpenGL handle for the atlas texture.

getTileSize()

public int getTileSize() { return tileSize; }

Returns the pixel size of each tile.

getGridSize()

public int getGridSize() { return gridSize; }

Returns the number of tiles per row/colum.

getAtlasSize()

public int getAtlasSize() { return atlasSize; }

Returns the total pixel width/height of the atlas image.