Open boytchev opened 1 week ago
- Create a WebGL renderer, a scene, a camera and render the scene. The background color is black.
- Create a WebGPU renderer, a scene, a camera and renderasync the scene. The background is white.
Actually, that is not quite true.
renderer = new THREE.WebGLRenderer(); // clear color is black; clear alpha is 1
renderer = new THREE.WebGLRenderer( { alpha: false } ); // clear color is black; clear alpha is 1
renderer = new THREE.WebGLRenderer( { alpha: true } ); // clear color is black; clear alpha is 0
And regardless of the backend,
renderer = new WebGPURenderer(); // clear color is black; clear alpha is 0
renderer = new WebGPURenderer( { alpha: false } ); // clear color is black; clear alpha is 1
renderer = new WebGPURenderer( { alpha: true } ); // clear color is black; clear alpha is 0
Thanks for the clarification. It's my bad I didn't check the alpha, I was only considering the visual effect.
So, in the vec3 interpretation of background color both renderers work the same, but sill in the vec4 interpretation they act differently.
This issue has two aspects. The value of clear alpha and whether the rendering context is created as transparent or opaque.
In WebGLRenderer
, the rendering context is always created with alpha: true
, regardless of the alpha
parameter. That has been done for performance reasons (see https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/WebGL_best_practices#avoid_alphafalse_which_can_be_expensive). The alpha
parameter just controls the clear alpha value. Since it is false
by default, the clear alpha value is 1
.
In WebGPURenderer
the implementation initially always created a transparent canvas but it has been made configurable via #27442. So the WebGPU backend can have a transparent or opaque canvas whereas the WebGL backend always creates its context with alpha: true
. However, since the alpha
parameter defaults to true
, the clear value is now 0
.
If we want to strictly align WebGPURenderer
to WebGLRenderer
, it would be necessary to set alpha
to false
in WebGPURenderer
and always create its context with premultiplied
as alphaMode
.
IMO, the default clear alpha value should be 1
and the clear color black. We have to agree on a policy in that regard, then we can file a PR.
Ideally, I would remove alpha
from WebGLRenderer
and let the clear color be defined by WebGLRenderer.setClearColor()
. In WebGPURenderer
I would also decouple the alpha
parameter from the clear alpha value. We can keep the parameter since there seem to be no performance issues with an opaque canvas like in WebGL but the clear alpha value should be changed to 1
.
Description
The default background color of
WebGLRenderer
is black. The default background color ofWebGPURenderer
is white.It will improve the consistency if both renderers have the same default background colors.
Reproduction steps
Code
(See the live examples for code)
Live example
Screenshots
WebGL black background (the canvas has red border):
WebGPU white background (the canvas has red border):
Version
r165
Device
Desktop
Browser
Chrome, Firefox
OS
Windows