Hi
Is flatshading broken in webgpu or Im I doing something wrong ?
Tried to make a sample here
Images from sample
Flat shading is implemented a bit different in both renderers. The root cause of the issue is an invalid geometry that you generate with SphereGeometry. Unlike WebGLRenderer, WebGPURenderer exhibits this issue.
thetaStart is set to 2 and thetaLength is set to the default Math.PI which means you create an inverted geometry which is not supported. The valid range of theta must be [0,Math.PI]. In your case it ends up [2, 2 + Math.PI].
If you just want to create the lower half of a sphere, do it like in: three.js dev template - module - JSFiddle - Code Playground
const sphere = new THREE.SphereGeometry(1.5, 15, 15, 0, Math.PI * 2, Math.PI * 0.5, Math.PI * 0.5 );
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@Mugen87
Thank you for fixing my weird sphere 
Updated my sample to show better the issue.
added toggle button for switching between lights
maybe Im doing someting wrong again 
left = webgl and light up like expected
right = webgpu, does not light up like it should
right = webgpu, light is lighting up the inside when it should not
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Now that is indeed a bug. The new materials system flips the normals although that is not required when using flat shading. I’ll file a PR with a fix:
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@Mugen87 Thank you 
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