WebGL2: Added Support for Multisampled Renderbuffers.

[Mugen87]

This PR adds support for multisampled renderbuffers. If you are using WebGL2, you can now perform "render-to-texture" and have an antialiasing render result. A post-process AA like FXAA is not necessary anymore.

Thanks to @mattdesl for his initial PR #8120

[mrdoob]

What happens if someone uses WebGLMultisampleRenderTarget while using WebGL 1? Should we fallback to normal WebGLRenderTarget in that case?

[Mugen87]

For now, I would not implement a fallback WebGLRenderTarget and refer to the documentation. It's clearly stated that it's a WebGL 2 feature. If people start to complain, we can still try to figure something out.

FYI: If you still try to use WebGLMultisampleRenderTarget without a WebGL 2 rendering context, you get a runtime error since certain API calls like blitFramebuffer are not available under WebGL 1.

[Mugen87]

Okay, d9c90c0 ensures that no runtime errors occur anymore. Instead, a warning is logged when WebGLMultisampleRenderTarget is used with WebGL1.

[mrdoob]

Thanks!

[Mugen87]

Yay 🎉 🙌 !

[carstenschwede]

Awesome! Would it be difficult to do the same for WebGLRenderTargetCube?

[Mugen87]

I'm not sure how much effort it takes but I think it should be possible. What is your use case for this?

Normally, multisampled FBOs are mainly used in context of post-processing.

[carstenschwede]

I use WebGLRenderTargetCube to simulate video projectors in THREE.js. The geometry that is being projected onto looks up its color according to the rendertarget texture. Your addition of multisampling renderbuffers allows better quality at lower resolutions and is much faster than manual MSAA. However, while a simple WebGLRenderTarget is sufficient for pinhole like projectors, I use a RenderTargetCube to project larger field of views using multiple projectors. The scenery is basically surrounded by a large envMap that is being dynamically rendered to using a RenderTargetCube. (Think of it like a planetarium).

Having a WebGLMultisampleRenderTargetCube would improve the rendering quality tremendously.

[mrdoob]

@carstenschwede Would you like to create a new issue for it?

[mrdoob]

@Mugen87 Would you like to explore removing WebGLMultisampleRenderTarget and adding multisample (default 0) and .setMultisample() to WebGLRenderTarget instead?

That way WebGLRenderTargetCube and WebGLMultipleRenderTargets will gain multisample support for free (API wise).

[Mugen87]

Okay, I'll have a look at this 👍 .

[Mugen87]

First draft: Mugen87@3d504a9

https://raw.githack.com/Mugen87/three.js/3d504a9328fa8d92c456310a45806c4f648eb22b/examples/webgl2_multisampled_renderbuffers.html

[carstenschwede]

Awesome! Just to be sure: This enables multisampling for WebGLCubeRenderTarget?

[Mugen87]

No, not yet. This PR adds no new features.

Cube map support is missing as well as resolving the multisampling to the default framebuffer (see #21573 and #22066).

[carstenschwede]

Thanks, I see, so API preparation for later support.