Point light source length produces artifacts at certain angles

  • This bug also exists in 4.18
  • This bug occurs with forward and deferred shading

When setting the source length of a point light to a value above 0, objects that are lit by it show artifacts, if the surface is at certain angles. These artifacts look identical to specular aliasing and are thus hidden by temporal anti aliasing. However, this is not a fix, since it would require TAA to be enabled at all times, which isn’t an option for low-end machines.

Steps to easily reproduce:

  1. Disable Anti-aliasing
  2. Create a new empty level
  3. Add a point light to it
  4. Set the source length to something like 100
  5. Add a sphere with a dark material to it
  6. Place the camera between the sphere and the light, so that the light is behind you (the artifacts are the most pronounced in this case)

At certain angles you will see white artifacts appear at the edges of the sphere. If the source length is set back to 0, the artifacts disappear. I’ve added an animated gif taken in my game to show the artifacts in motion, because that’s when it starts to look really awful.

(View at full size to see the artifacts)



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