Bug 49996

Configuration:
- Intel SandyBridge PC Mainboard DH61AG and integrated Intel HD Graphics 3000
- Dual OS: Windows 7 32bit and Ubuntu 12.04 32bit

When using OpenGL sampler objects for configuring textures, on Ubuntu Linux you have to create a mipmap chain by calling “glGenerateMipmap()”. Otherwise the texture sampling will not work (e.g. returns black).
Take the following example:
// Init
int texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(…);

int sampler;
glGenSamplers(1, &sampler);
glSamplerParameteri(sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glSamplerParameteri(sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

// Render loop
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glBindSampler(0, sampler);
…

This works perfectly on Windows but not on Ubuntu Linux. For Ubuntu Linux I have to add the following:
//Init
…
glTexImage2D(…);
glGenerateMipmap(GL_TEXTURE_2D);

Without the mipmap the texture sampling does not work, although mipmaps are not used. When using the traditional texture filter configuration, this problem does not occur and the code behaves the same on Windows and Linux:
// Render loop
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);