So I have an AtlasTexture that contains all the tiles I need to draw a tile map.
Right now I pass the AtlasTexture through a uniform, and the idea is to change the texture coordinate to select just the portion I need from the atlas.
The issue is that I can only specify on the fragment shader to cut the texture from the zero origin, is it possible to specify an offsetX to tell to the shader where I want to start drawing?
float vertices[] = {
// aPosition // aTextureCoordinate
0.0f, 0.0f, 0.0f, 0.0f,
100.0f, 0.0f, 1.0f, 0.0f,
0.0f, 100.0f, 0.0f, 1.0f,
100.0f, 100.0f, 1.0f, 1.0f,
};
uint32_t indices[] = {0, 1, 2, 2, 3, 1};
Vertex shader
#version 330 core
layout(location = 0) in vec2 aPosition;
layout(location = 1) in vec2 aTextureCoordinate;
out vec2 textureCoordinate;
void main() {
gl_Position = vec4( aPosition.x, aPosition.y, 1.0f, 1.0f);
textureCoordinate = vec2(
aTextureCoordinate.x / 3.0f, // This selects the first tile in the uAtlasTexture
aTextureCoordinate.y
);
}
Fragment shader
#version 330 core
in vec2 textureCoordinate;
uniform sampler2D uAtlasTexture; // Has 3 tiles
out vec4 color;
void main() {
color = texture(uAtlasTexture, textureCoordinate);
}
Use an Uniform variable for the offset. `vec2(1.0/3.0 + aTextureCoordinate.x / 3.0f, aTextureCoordinate.y); "selects2 the 2nd tile. Use a uniform instead of 1.0/3.0:
#version 330 core
layout(location = 0) in vec2 aPosition;
layout(location = 1) in vec2 aTextureCoordinate;
out vec2 textureCoordinate;
uniform float textureOffsetX;
void main() {
gl_Position = vec4( aPosition.x, aPosition.y, 1.0f, 1.0f);
textureCoordinate = vec2(
textureOffsetX + aTextureCoordinate.x / 3.0f,
aTextureCoordinate.y
);
}
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