I'm learning OpenGL 3.3 trying to do the following (as it is done in D3D)...

• Create Texture of Width, Height, Pixel Format
• Map texture memory
• Loop write pixels
• Unmap texture memory
• Set Texture
• Render

Right now though it renders as if the entire texture is black.

I can't find a reliable source for information on how to do this though. Almost every tutorial I've found just uses glTexSubImage2D and passes a pointer to memory.

Here is basically what my code does... (In this case it is generating an 1-byte Alpha Only texture but it is rendering it as the red channel for debugging)

GLuint pixelBufferID;
glGenBuffers(1, &pixelBufferID);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID);
glBufferData(GL_PIXEL_UNPACK_BUFFER, 512 * 512 * 1, nullptr, GL_STREAM_DRAW);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

GLuint textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, 512, 512, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr);
glBindTexture(GL_TEXTURE_2D, 0);

glBindTexture(GL_TEXTURE_2D, textureID);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID);
void *Memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY);
// Memory copied here, I know  this is valid because it is the same loop as in my working D3D version
glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

And then here is the render loop.

// This chunk left in for completeness
glUseProgram(glProgramId);
glBindVertexArray(glVertexArrayId);
glBindBuffer(GL_ARRAY_BUFFER, glVertexBufferId);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, 0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 20, 12);
GLuint transformLocationID = glGetUniformLocation(3, 'transform');
glUniformMatrix4fv(transformLocationID , 1, true, somematrix)

// Not sure if this is all I need to do
glBindTexture(GL_TEXTURE_2D, pTex->glTextureId);
GLuint textureLocationID = glGetUniformLocation(glProgramId, "texture");
glUniform1i(textureLocationID, 0);

glDrawArrays(GL_TRIANGLES, Offset*3, Triangles*3);

Vertex Shader

#version 330 core

in vec3 Position;
in vec2 TexCoords;
out vec2 TexOut;
uniform mat4 transform;

void main()
{
    TexOut = TexCoords;
    gl_Position = vec4(Position, 1.0) * transform;
}

Pixel Shader

#version 330 core

uniform sampler2D texture;
in vec2 TexCoords;
out vec4 fragColor;

void main()
{
   // Output color
   fragColor.r = texture2D(texture, TexCoords).r;
   fragColor.g = 0.0f;
   fragColor.b = 0.0f;
   fragColor.a = 1.0;
}