Renderer: Stencil Buffer disabled in RenderContext by default

[RenaudRohlinger]

Related: #27900

Description

Following #27900, this PR disable the Stencil Buffer by default in RenderContext.

This contribution is funded by Utsubo

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
669.7 kB (166.1 kB)	669.7 kB (166.1 kB)	+0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

Filesize dev	Filesize PR	Diff
449.9 kB (108.8 kB)	449.9 kB (108.8 kB)	+0 B

[gkjohnson]

I don't know if I agree that the default of the clear flag should be changed. If I have the stencil buffer enabled why should calling "clear" not clear the stencil buffer, as well?

The flag for enabling the stencil buffer by default is separate from when it get cleared by default when it exists.

[Mugen87]

How about not changing the default parameter in the clear() methods but check instead if stencil/stencilBuffer(for render targets) has been set to true or not? If so, the stencil clear is performed.

[Mugen87]

webgl_postprocessing_advanced and webgl_postprocessing_masking fail now. Both use the stencil buffer.

This PR should not introduce a breaking change.

[RenaudRohlinger]

Ok, what about this one?

the WebGPURenderer part is pretty straight forward since we have this.stencil exposed to the renderer but for the WebGLRenderer it looks like this:

if ( _currentRenderTarget === null ) {

	stencil = this.autoClearStencil;

} else if ( _currentRenderTarget.stencilBuffer === false ) {

	stencil = false;

}

[Mugen87]

Ok, what about this one?

I think this looks good!

[gkjohnson]

Just to be clear - are we really worried about performance implications of setting the "clear stencil" bit when there's no stencil buffer created? This seems very much like a micro optimization that adds unnecessary code for something the driver would have to do anyway.

[RenaudRohlinger]

I agree that adjusting the "clear stencil" bit without an existing stencil buffer likely won't impact performance, as it only modifies settings for the gl.clear() command without any substantial processing.
But to me, it just makes more sense to not bother with it if we don’t have a stencil buffer in the first place. Why clear something that’s not there? Considering how different GPUs might react, keeping things simple and logical feels like the better move.

[gkjohnson]

Why clear something that’s not there? Considering how different GPUs might react, keeping things simple and logical feels like the better move.

I'll defer to other opinions here but my opinion is that defensively adding code to do things we don't know are needed isn't a great policy. It adds more code which means more to understand (and in this case the purpose or intent isn't obvious) and more points for potential bugs to arise, however simple the logic may seem. I think there are good reasons to not just add things that seem simple without an apparent need.

Regarding driver issues - I think you do have to trust the drivers to do something reasonable until it's shown they don't in some case. Otherwise what's to stop you from adding defensive code everywhere?

[RenaudRohlinger]

Alright you convinced me @gkjohnson. I will just continue the previous work and disable by default the stencil buffer in the WebGPU part too on this PR.