Strange patterns from SPOT lamp

Support Materials and Textures
1

Hey, My first post!

I’m observing unusual patterns when using a SPOT lamp. The first pic is with a ‘spotSize’ setting of 90 deg. the second is 30 deg. The incidence angle also affects the extent of these patterns. I imagine there are workarounds such as ‘shadow only’ and using a different type of lamp for the light source but I’d sure like to know if there might be a setting for my graphics card or something else to avoid this behaviour.

skyduster

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2

what happens if you turn bias up?

3

Good call!

Tweaking the bias is not something I would intuitively try… but I knew that one of you great blenderartists would set me in the right direction.

It appears that the procedure should be to:

  1. Try to avoid a very shallow angle of incidence if possible
  2. Reduce the ‘SpotSize’ angle as much as possible
  3. Adjust the ‘bias’ upward till the result is acceptable

These two pics show the result of these steps. In the first the ‘SpotSize’ has been reduced to 8 deg. and in the second the bias was set to 2.2.

Thanks again,

skyduster

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4

Huh. I think another problem would be resolution. You see, it was blocky at a 90 degree angle, cause the shadow map is stretched across a wide range, it appeared more high res at a smaller angle, because the same sized shadow map was stretched across much less space. Shadow buffer maps are really just propagating bunches of of bitmaps arranged in series, so–just like stretching a texture across a large area would pixelate it–making the spotlight wide-angle will distort it similarly.

5

skyduster, would you like to be a wiki contributor?

6

Roger;
I appreciate your ‘invitation’. Someday I may find myself in a more comfortable ‘situation’…
If so I would indeed consider trying to make some contribution to the community.

Thanks,
skyduster