'Trouble with imageStore() (OpenGL 4.3)

I'm trying to output some data from compute shader to a texture, but imageStore() seems to do nothing. Here's the shader:

#version 430

layout(RGBA32F) uniform image2D image;

layout (local_size_x = 1, local_size_y = 1) in;
void main() {
    imageStore(image, ivec2(gl_GlobalInvocationID.xy), vec4(0.0f, 1.0f, 1.0f, 1.0f));
}

and the application code is here:

GLuint tex;

glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, WIDTH, HEIGHT, 0, GL_RGBA, GL_FLOAT, 0);

glBindImageTexture(0, tex, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA32F);
glUseProgram(program->GetName());
glUniform1i(program->GetUniformLocation("image"), 0);

glDispatchCompute(WIDTH, HEIGHT, 1);

then a full screen quad is rendered with that texture but currently it only shows some random old data from video memory. Any idea what could be wrong?

EDIT:

This is how I display the texture:

// This comes right after the previous block of code
glUseProgram(drawProgram->GetName());

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex);
glUniform1i(drawProgram->GetUniformLocation("sampler"), 0);

glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, 6);

glfwSwapBuffers();

and the drawProgram consists of:

#version 430
#extension GL_ARB_explicit_attrib_location : require

layout(location = 0) in vec2 position;
out vec2 uvCoord;

void main() {
    gl_Position = vec4(position.x, position.y, 0.0f, 1.0f);
    uvCoord = position;
}

and:

#version 430

in vec2 uvCoord;
out vec4 color;

uniform sampler2D sampler;

void main() {
    vec2 uv = (uvCoord + vec2(1.0f)) / 2.0f;
    uv.y = 1.0f - uv.y;

    color = texture(sampler, uv);
    //color = vec4(uv.x, uv.y, 0.0f, 1.0f);
}

The last commented line in fragment shader produces this output: Render output

The vertex array object (vao) has one buffer with 6 2D vertices:

-1.0, -1.0

1.0, -1.0

1.0, 1.0

1.0, 1.0

-1.0, 1.0

-1.0, -1.0

opengltexturesshadercompute-shader


Solution 1:[1]

GL_RGBA is not a sized internal format and so you're not able to know which it is really. Most often, it is transformed to GL_RGBA8 by OpenGL.

In your case, the GL_FLOAT parameter you set only describes the pixel data you could upload in the texture.

Read the table 2 here to know what you can set as an internal texture format.

Solution 2:[2]

Okay I found the solution. The problem lies here:

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, WIDTH, HEIGHT, 0, GL_RGBA, GL_FLOAT, 0);

this line doesn't specify the size of the internal format (GL_RGBA). When I supplied GL_RGBA32F it started working. Why that is a problem, I don't know (hopefully somebody will be able to explain).

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Scheff's Cat
Solution 2 Endox

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