While in WebGL 1 all texture parameters are per texture, in WebGL 2, we can optionally use sampler objects. By using samplers, we can move all texture parameters to a sampler, allowing a single texture to be sampled in different ways.
In WebGL 1, texture image data and sampling information (which tells GPU how to read the image data) are both stored in texture objects. It can be painful when we want to read from the same texture twice but with a different method (say, linear filtering vs nearest filtering) because we need to have two texture objects. With sampler objects, we can separate these two concepts. We can have one texture object and two different sampler objects. This will result in a change in how our engine organize textures.
Here’s an example:
const samplerA = gl.createSampler();
gl.samplerParameteri(samplerA, gl.TEXTURE_MIN_FILTER, gl.NEAREST_MIPMAP_NEAREST);
gl.samplerParameteri(samplerA, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.samplerParameteri(samplerA, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.samplerParameteri(samplerA, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
const samplerB = gl.createSampler();
gl.samplerParameteri(samplerB, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_LINEAR);
gl.samplerParameteri(samplerB, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.samplerParameteri(samplerB, gl.TEXTURE_WRAP_S, gl.MIRRORED_REPEAT);
gl.samplerParameteri(samplerB, gl.TEXTURE_WRAP_T, gl.MIRRORED_REPEAT);
// ...
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.bindSampler(0, samplerA);
gl.activeTexture(gl.TEXTURE1);
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.bindSampler(1, samplerB);