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Note: I'm using the WebGPU build 167 of three.js for this question and JSFiddle.

See screenshot and JSFiddle. I have a simple sphere between two "floors", with a DirectionalLight pointing straight down from above. Notice how the sphere casts a shadow on the top "floor". How can I remove the shadow from the top floor? I don't want to disable the top floor's ability to receive shadows from other objects though, so I don't want to set receiveShadow = false on the top floor mesh.

JSFiddle: https://jsfiddle.net/0fwkyvu6

three.js GitHub bug report: https://github.com/mrdoob/three.js/issues/29200

I also posted the question on the three.js community discourse: https://discourse.threejs.org/t/duplicate-shadow-shadow-appears-below-and-above-object-webgpu-build-167/69481

Update 1: setting logarithmicDepthBuffer: false appears to fix the issue somewhat, however the logarithmic depth buffer is a requirement for my scene, so I'd like to get the shadow working with it.

Update 2: the top shadow is not visible in the standard WebGLRenderer build of three.js, so there must be some issue specifically with the WebGPU build.

enter image description here

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  • See jsfiddle.net/vb179y4r I spent some time cleaning up your code and it appears to work. Perhaps you can see if you can figure out what is different... Commented Aug 20, 2024 at 20:07
  • @WestLangley Thanks for taking a look at this. I checked out your edits, and I saw you removed logarithmicDepthBuffer--I need to have logarithmicDepthBuffer enabled for other things in the scene, if you add logarithmicDepthBuffer: true to your JSFiddle then the top shadow appears again. Commented Aug 20, 2024 at 20:29
  • OK, so you have your answer... A reasonable guess is WebGPURenderer does not yet support logarithmicDepthBuffer for Orthographic (shadow) cameras. Commented Aug 20, 2024 at 21:01
  • Here I changed your fiddle to use a SpotLight: jsfiddle.net/847uqt2j Commented Aug 20, 2024 at 21:07
  • @WestLangley once again thanks for looking into this. It still creates the duplicate shadow however if you move the spotlight's position up a little: jsfiddle.net/heb3tg50/1 Commented Aug 20, 2024 at 21:50
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