Custom Blending in WebGPU

[MrsDarth]

Description

Using custom blending in materials in webgpu will throw an error if the alpha blending is not specified.

The cause is because the default values are set to GPUBlendFactor which is then passed to _getBlendFactor which is wrong
https://github.com/mrdoob/three.js/blob/dev/examples/jsm/renderers/webgpu/utils/WebGPUPipelineUtils.js#L192

Reproduction steps

1. Create a material with custom blending
2. Do not specify blend alpha

Code

const material = new MeshBasicNodeMaterial();
material.blending = CustomBlending;
material.blendEquation = AddEquation;
material.blendSrc = OneFactor;
material.blendDst = OneMinusSrcColorFactor;

Live example

none

Screenshots

No response

Version

r162

Device

No response

Browser

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OS

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[Mugen87]

Fixed via #28490.