Hey there! Let's break down your questions about OpenGL texture binding with layout bindings clearly:

1. Is using GL_TEXTURE0 + 3 correct for binding the first texture? #

Short answer: It depends on your shader's layout binding declaration—but if your shader specifies the sampler's binding point as 3, then yes, this is the correct approach.

Here's the context:
When you declare a sampler in your shader like this:

// Fragment shader example
layout(binding = 3) uniform sampler2D myFirstTexture;

The binding = 3 tells OpenGL that this sampler should use texture unit 3. Since OpenGL's texture unit constants start at GL_TEXTURE0 (which is equivalent to integer 0), GL_TEXTURE0 + 3 resolves to the constant for texture unit 3.

On the CPU side, you'd bind your texture like this to match:

// Activate the correct texture unit first
glActiveTexture(GL_TEXTURE0 + 3);
// Bind your texture object to this unit
glBindTexture(GL_TEXTURE_2D, myTextureID);

This works regardless of whether it's your "first" texture or not—what matters is that the shader's binding number matches the texture unit you activate/bind to.

2. Are samplers bound independently from other uniforms? #

Absolutely—samplers and regular uniforms (like vec3, mat4, or UBOs) use separate, independent binding name spaces.

This means you can have a regular uniform with layout(binding = 3) and a sampler also with layout(binding = 3) and they won't conflict at all. OpenGL treats these as distinct resource types:

• Regular uniforms (or UBOs) are bound to uniform buffer binding points or direct uniform locations.
• Samplers are linked to texture units, which have their own set of binding points managed separately.

That said, it's still a good practice to plan out your binding point ranges (e.g., reserve 0-2 for UBOs, 3-7 for samplers) to keep your code organized and avoid confusion.

内容的提问来源于stack exchange，提问作者Gediminas