moiré effect on DSM shadow maps

[rob]

I am just rendering simple 1k shadow maps with a shadow softness set to 1. You dont quite notice it at first but you get a slight moiré effect on the map. But when you use DSM merge to merge 3 maps it becomes really bad all over .Has anyone seen this before using the DSM merge.

I have tried altering the bias on the 3 lights I have creating the shadowmaps to some effect but whn I use the DSM merge t really does bring into stark relief the moire pattern all over the image. Any ideas ?

Edited August 24, 2009 by rob

[brianburke]

Hi rob. I don't know what might cause this problem (if its not selfshadowing issue fixable with bias), but I think you'll find that if you exclude the ground plane from the shadow creation render you'll fix the artifact and speed up this render as well. This can be done always for objects that receive shadows but don't cast shadows.

Hope this helps.

[rob]

Hi Brian , yes normally in renderman / mantra a dabble with the bias clears it up. Its interesting that the DSM merge tool increases the effect and adds it to areas where it was not apparent.

r

[junaid]

just for another way out, you might want to give it a go by increasing shadow samples and see.

Cheers,

Junaid

Hi Brian , yes normally in renderman / mantra a dabble with the bias clears it up. Its interesting that the DSM merge tool increases the effect and adds it to areas where it was not apparent.

r

[Wolfwood]

I'd also do a test by setting DSM Compression down to 0 (default is 5).