Create and use floating point texture in OpenGL

Question

I am trying to create floating point texture in OpenGL. I have 4 vertexes (2 polygons) forming square: ``` ------- |\ | | \ | | \| ------- ``` Now I want to create texture with float values, each value of texture to represent basic color intensity of each pixel. I want to calculate pixel color in fragment shader like this: ``` color = texture2D(texture, coordinates).r * vec4(0.4, 1.0, 0.8, 1.0); ``` vec4(0.4, 1.0, 0.8, 1.0) is just basic color I use When I prepare data like this: ``` int width, height; width = 16; height = 16; float data[16][16]; for(int i = 0; i < width; i++){ for(int j = 0; j < height; j++){ data[i][j] = 0.5f; } } GLuint n_tex_surface; glGenTextures(1, &n_tex_surface); glBindTexture(GL_TEXTURE_2D, n_tex_surface); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, data); glGenerateMipmap(GL_TEXTURE_2D); ```…

Accepted Answer

You are only allocating enough storage for 1/4 of your texture.

You need to use `float data[16][16][4]` and then assign each component of the texture a value of `0.5f`:

```
int width, height;
width = 16;
height = 16;
float data[16][16][4];
for(int i = 0; i < width; i++){
    for(int j = 0; j < height; j++){
        data[i][j][0] = 0.5f;
        data[i][j][1] = 0.5f;
        data[i][j][2] = 0.5f;
        data[i][j][3] = 0.5f;
    }
}
```

You are actually lucky that doing what you originally tried did not crash your software. You are/were forcing GL to overrun your allocated storage when it reads the texture image data.

Create and use floating point texture in OpenGL

Solution

Problem