Description

A couple examples:

• https://discourse.threejs.org/t/shadow-banding-with-webgpurenderer-vsmshadowmap/89017/3
• https://discourse.threejs.org/t/hide-line-from-shadow/53656

Reproduction steps

1. Here's the webgpu VSM example with some debug helpers enabled, and also the spotlight frustum is tighter to more closely encompass the example: https://jsfiddle.net/s79ack12
   No issue so yet:
   
2. When we tighten up the spotlight's shadow.focus, we can see a line at the edge of the spotlight's shadow map area: https://jsfiddle.net/zm53Ladu (line 87)
   This is not typical shadow acne, as it happens exclusively along the edge of the shadow map area:
   
3. A workaround is to patch THREE.ShadowNode.prototype.setupShadowFilter to set shadow pixels to 1 inside of a border around the shadow map area. In this example, fading the shadow out (or more technically, fading the light back in): https://jsfiddle.net/4675h9j8
   No more map edge artifact:
   
   (it doesn't need to be a fade, it could be a hard drop off around the edges, but I also wanted a configurable fade in my case).

Code

The problem becomes apparent (at least in this scnenario) with this particular line:

spotLight.shadow.focus = 0.3

Live example

above

Screenshots

above

Version

r182, macOS 26 Safari 26

Device

Desktop

Browser

Safari

OS

MacOS