OpenGL black textures - c++

Question

When trying to render a 2D label using a bitmap texture, my texture sampling returns black. I tried debugging using RenderDoc but I can't find the problem. It seems the texture loads fine and is stored in the correct register, but it still renders black.
I even tried using a full red texture to check the texture coordinates, but the texture still showed up as black.
Here is the code I use for loading/rendering the texture. It tried to render a label. (genMipMaps is false).
void Texture::CreateGLTextureWithData(GLubyte* data, bool genMipMaps) {
if (bitmap)
glDeleteTextures(1, &bitmap);
glGenTextures(1, &bitmap);
glBindTexture(GL_TEXTURE_2D, bitmap);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
if (genMipMaps)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
else
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.x, size.y, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
if (genMipMaps)
glGenerateMipmap(GL_TEXTURE_2D);
}
Custom sampler:
glGenSamplers(1, &linearSampler);
glSamplerParameteri(linearSampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glSamplerParameteri(linearSampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glSamplerParameteri(linearSampler, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
glSamplerParameteri(linearSampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glSamplerParameteri(linearSampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glSamplerParameteri(linearSampler, GL_TEXTURE_COMPARE_FUNC, GL_NEVER);
glSamplerParameterf(linearSampler, GL_TEXTURE_MIN_LOD, 0);
glSamplerParameterf(linearSampler, GL_TEXTURE_MAX_LOD, GL_TEXTURE_MAX_LOD);
glBindSampler(0, linearSampler);
Rendering:
glDisable(GL_DEPTH_TEST);
glDisable(GL_STENCIL_TEST);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glActiveTexture(GL_TEXTURE0 + 0);
glBindTexture(GL_TEXTURE_2D, texture->getBitmap());
// Set index and vertex buffers
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
if (glIsBuffer(vertBuffer) && vertBuffer != lastVertBuffer)
glBindBuffer(GL_ARRAY_BUFFER, vertBuffer);
if (glIsBuffer(indexBuffer) && indexBuffer != lastIndexBuffer)
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
shader->updateLayout();
// Draw
const void* firstIndex = reinterpret_cast<const void*>(0);
glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, firstIndex);
glBindVertexArray(0);
Shaders:
VS:
#version 430 core
// Vertex atributes
in vec3 a_position;
in vec2 a_texture;
in vec4 a_color;
// Constant buffers
layout(std140) uniform VertexBlock
{
mat4 u_wvp;
mat4 u_world;
};
// Vertex shader outputs
out vec2 v_texture;
out vec4 v_color;
void main()
{
v_texture = a_texture;
v_color = a_color;
gl_Position = u_wvp * vec4(a_position, 1.0);
}
FS: (I tried setting the color to red without using the texture and it renders in red correctly.)
#version 430 core
in vec4 v_color;
in vec2 v_texture;
layout(binding = 0) uniform sampler2D u_texture;
out vec4 fragColor;
void main()
{
fragColor = v_color * texture(u_texture, v_texture);
}

Answer 1

Found out what the problem was. I was not generating mipmaps for the 2D textures but the sampler was still using them.
Texture loading:
...
if (genMipMaps)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
else
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.x, size.y, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
if (genMipMaps)
glGenerateMipmap(GL_TEXTURE_2D);
...
Sampler:
...
glSamplerParameteri(linearSampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glSamplerParameteri(linearSampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
...
What I did to fix it is just always generate mipmaps for the textures