What is the difference between glTexParameter and glSamplerParameter

Question

Because I am no expert, please dont consider this question silly. I have read several tutorials where texture parameters were set using glTexParameter. I am talking about GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER , GL_TEXTURE_WRAP_R etc.. Suddenly I come across a tutorial that now used glSamplerParameter to set these parameters.

I see there are some common parameters between glTexParameter and glSamplerParameter like (GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER , GL_TEXTURE_WRAP_R, GL_TEXTURE_MIN_LOD etc), and there are some that are only applicable in glTexParameter (GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_SWIZZLE_R etc). I perfectly understand the uncommon ones because after all, the glTexParameter is acting on the image, and these parameters are specifying attributes image per se.

But I dont quite understand why are there some parameters that are common between these 2 GL calls. Which should be used when? In my opinion sampling parameters like (GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER , GL_TEXTURE_WRAP_R, etc) should only be applicable to sampler (glSamplerParameter) and not to glTexParameter.

Please help me understand the difference between two.

Answer 1

glSamplerParameter is relatively new. The way a texture is sampled is actually a property of the thing doing the sampling, not of the texture itself — not just in semantic terms but on actual, real hardware.

Besides the desire to represent things as they actually function on the hardware, tying two unrelated things together can cost you in performance terms. If you make the way something is sampled a property of the sampler then e.g. you can sample the same texture in two different ways within the same shader. If it's a property of the texture then you're going to have to upload the same texture twice or write a multi-pass shader.

Hence the two things are now being separated.