CODEWITHSUNDEEP
openglgraphicstexturesshader
user3794176
user3794176

Reputation: 85

Why Texture Unit number is limited in OpenGL?

As I understand we store texture in GPU memory with glTexImage2D function and there is no limited number theoretically. However, when we try to use them there is a limitation which is 32 texture units GL_TEXTURE0 to GL_TEXTURE31. Why is there this limitation?

Upvotes: 2

Views: 1129

Answers (1)

Nicol Bolas
Nicol Bolas

Reputation: 473212

The limitation in question (which as mentioned in the comments, is the wrong limit) is on the number of textures that can be used with a single rendering command at one time. Each shader stage has its own limit on the number of textures it can access.

This limitation exists because hardware is not unlimited in its capabilities. Textures require resources, and some hardware has limits on how many of these resources can be used at once. Just like hardware has limits on the number of uniforms a shader stage can have and so forth.

Now, there is some hardware which is capable of accessing texture data in a more low-level way. This functionality is exposed via the ARB_bindless_texture. It's not a core feature because not all recent, GL 4.x-capable hardware can support it.

Upvotes: 2

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