Argthtjtr

I have written a very simple OpenGL program using glfw and glew. It compiles fine and runs, but the simple texture I am passing to the fragment shader is not being displayed.

The only geometry is a single quad.

I am only trying to display a single solid color, the first element of the texture. I know that the fragment shader works at all because I can display a solid color without the texture:

#version 320 es

mediump out vec4 color;

precision mediump float;

precision mediump sampler2D;



in vec2 texCoord;

uniform sampler2D tex;



void main() {

    color = vec4(0.5, 0.75, 0.5, 1.0);

}

However, when I use the texture sampler I get nothing, like the sampler is sampling only 0s (changing only main()):

void main() {

    color = vec4(texture(tex, vec2(0, 0)).rgb, 1);

}

I am populating and generating the texture in what I believe is the correct manner (TEX_SIZE is defined as #define TEX_SIZE (32*32)):

//Texture Data

GLfloat texData[TEX_SIZE * 3] = {1.0};



//Create texture

GLuint tex;

glGenTextures(1, &tex);

glActiveTexture(GL_TEXTURE0);

glBindTexture(GL_TEXTURE_2D, tex);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 32, 32, 0, GL_RGB, GL_FLOAT, texData);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_REPEAT);

And here is the entire draw loop:

//Render loop

while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS

    && !glfwWindowShouldClose(window)) {

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);



    glUseProgram(programID);



    //Texture

    glActiveTexture(GL_TEXTURE0);

    glBindTexture(GL_TEXTURE_2D, tex);

    glUniform1i(glGetUniformLocation(programID, "tex"), 0);



    //Draw the quad

    glEnableClientState(GL_VERTEX_ARRAY);

    glVertexPointer(3, GL_FLOAT, 0, gVertices);

    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, gIndices);

    glDisableClientState(GL_VERTEX_ARRAY);



    if (glGetError()) {

        puts((char *)glewGetErrorString(glGetError()));

    }



    glfwSwapBuffers(window);

    glfwPollEvents();

}

Why is this happening? I'm totally stuck.

EDIT: Changed the array initialization, as per suggestion:

//Texture Data

GLfloat texData[TEX_SIZE * 3];

for (int i = 0; i < TEX_SIZE * 3; i++) {

    texData[i] = 1.0;

}

There was no change. Output is still all black.

The initial value of GL_TEXTURE_MIN_FILTER is GL_NEAREST_MIPMAP_LINEAR. But you don't generate mipmaps. This causes that the texture is not complete.

OpenGL ES 3.2 Specification; 8.17 Texture Completeness; page 205

A texture is said to be complete if all the texture images and texture parameters
required to utilize the texture for texture application are consistently defined.

... a texture is complete unless any of the following
conditions hold true:

• The minification filter requires a mipmap (is neither NEAREST nor LINEAR),
  and the texture is not mipmap complete.

Change the texture minification filter (glTexParameteri) to solve your issue:

e.g.

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);