Unnecessary memory allocations when using multisampled render targets

[codedpalette]

Description

I'm using EffectComposer to render to WebGLRenderTarget with samples > 0. My understanding is that it should create 2 render targets, and for each of them it should create 1 framebuffer, and two renderbuffers (1 color and 1 depth). However, when I inspect allocated memory with https://github.com/greggman/webgl-memory, I see that each render target creates 2 framebuffers, 3 renderbuffers and 1 texture. Looking at the code of WebGLTextures.setupRenderTarget I see there are two separate framebuffers, __webglFramebuffer and __webglMultisampleFramebuffer, with 2 multisample render buffers bound to the latter, and texture and regular depth buffer bound to the former. Yet when I look at the code in WebGLRenderer I see that __webglFramebuffer is never bound to anything when using multisample render target. My question is: is it a bug? Am I missing something?

Solution

Multisample render target should only allocate 1 framebuffer and 2 multisample render buffers

Alternatives

Additional context

No response

[Mugen87]

Yet when I look at the code in WebGLRenderer I see that __webglFramebuffer is never bound to anything when using multisample render target.

It is bound, e.g. in updateMultisampleRenderTarget():

three.js/src/renderers/webgl/WebGLTextures.js

Lines 1992 to 1993 in 92eae7d

	state.bindFramebuffer( _gl.READ_FRAMEBUFFER, renderTargetProperties.__webglMultisampledFramebuffer );
	state.bindFramebuffer( _gl.DRAW_FRAMEBUFFER, renderTargetProperties.__webglFramebuffer );

Without it, a resolve won't work unless WEBGL_multisampled_render_to_texture is supported.

If you think the resolve uses redundant resources, feel free to file a PR that demonstrated you suggested changes.