Changing internal format causes texture to have incorrect parameters-CodePudding

I set up framebuffer texture on which to draw a scene on as follows:

glGenFramebuffers(1, &renderFBO);

glGenTextures(1, &renderTexture);
glBindTexture(GL_TEXTURE_2D, renderTexture);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, W_WIDTH, W_HEIGHT, 0, GL_RGBA, GL_FLOAT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

int width, height;

glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width);
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &height);

cout << "width: " << width << " height: " << height << endl;

glBindFramebuffer(GL_FRAMEBUFFER, renderFBO);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, renderTexture, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);

By validating width and height, they do indeed have the correct dimensions, 1024, 768.

Now I am trying to set up a second texture, to be used as a counter, meaning I am trying to count the occurences of every color value, by incrementing the appropriate texel in the texture. Since I am trying to count the colors, I use a 2D texture of size 256 x 3. In each cell I want a single unsigned integer, showing the number of times a specific color value has appeared up until that point. For instance, if the color (255,5,3) was encountered, I would to increment the numbers inside tex[255][0], tex[5][0], tex[3][0]

num_bins = 256;
GLuint* hist_data = new GLuint[num_bins * color_components]();

glGenTextures(1, &tex_output);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex_output);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R32UI, 256, 3, 0, GL_RED, GL_UNSIGNED_INT, hist_data);
glBindImageTexture(0, tex_output, 0, GL_FALSE, 0, GL_READ_WRITE, GL_R32UI);

int width, height;
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width);
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &height);
cout << "width: " << width << " height: " << height << endl;

I used the sized and base internal format correspondence shown in the opengl specification. However when this code executes the output values are width=0, height=0. The input data doesn't seem to be the issue, because I tried providing NULL as the last argument and it still didn't work. What am I missing here?

EDIT:

Incrementation of the values in the texture is supposed to happen inside the following compute shader:

#version 450
layout(local_size_x = 1, local_size_y = 1) in;
layout(rgba32f, binding = 0) uniform image2D img_input;
layout(r32ui, binding = 1) uniform uimage2D img_output;

void main() {

  // grabbing pixel value from input image  
  vec4 pixel_color = imageLoad(img_input, ivec2(gl_GlobalInvocationID.xy));

  vec3 rgb = round(pixel_color.rgb * 255);

  ivec2 r = ivec2(rgb.r, 0);
  ivec2 g = ivec2(rgb.g, 1);
  ivec2 b = ivec2(rgb.b, 2);

  uint inc = 1;

  imageAtomicAdd(img_output, r, inc);
  imageAtomicAdd(img_output, g, inc);
  imageAtomicAdd(img_output, b, inc);
}

CodePudding user response：

You get a GL_INVALID_OPERATION error, because the texture format argument doesn't correspond with the internal format of the texture. For an unsigned integral format you have to use GL_RED_INTEGER instead of GL_RED (see glTexImage2D):

~~glTexImage2D(GL_TEXTURE_2D, 0, GL_R32UI, 256, 3, 0, GL_RED, GL_UNSIGNED_INT, hist_data);~~

glTexImage2D(GL_TEXTURE_2D, 0, GL_R32UI, 256, 3, 0, GL_RED_INTEGER, GL_UNSIGNED_INT, hist_data);

I recommend using Debug Output, it saves a lot of time and lets you find such errors quickly.