Mental Ray shadow artifacts -help!

[andrew trask]

hey everyone. Like the title says, I'm getting some shadow artifacts with Mental Ray.

This is my first test scene using MR. I am using IES lights, btw (is that not badass technology or what -i just became aware of the whole IES thing).

The first renders i was testing, I set the lights to mental ray shadow map. -didn't cast any shadows (do IES lights not support MRshadowmaps?) So, I set the shadows to raytraced. It looked good, but I don't like the harsh shadows. I tried regular shadow map and the shadows look great -except for the artifacts.

I bumped up the shadowmap size from 512 to 1024, which helped the artifact problem, but there were still some floating around. I even bumped it up to 2048 but there was not much difference from 1024.

Can anyone help me out?

I attached the render and the settings of the lights for this render

thanks in advance

[William Alexander]

Almost looks like modeling issues, the artifacts seem to follow edges of faces. Post a wireframe shot?

Smoothing groups may take care of it

WDA

[andrew trask]

ok, i took the scene down to its most basic form and checked the smoothing groups on the walls (just a simple box)

here are the results...


[edit -

1st image is shadowmap @ 512
2nd - shadowmap @ 1024
3rd - wireframe
4th - raytraced shadows

/edit]

[Philip De keersmaecker]

use the raytrace shadows together with mr area light
change the mr area for softer shadows
make sure to use M7 because M6 mr does not support IES

[andrew trask]

...I set the shadows to raytraced. It looked good, but I don't like the harsh shadows.

I need to use IES, not MR lights.

is there a way to get smooth raytraced shadows using IES lights? and why can't I get any shadows using MRshadowmap?


yes, I'm using max7

[Philip De keersmaecker]

snorry : misunderstood
why dont you use the "target area light" and set the web to your ies file ?
then you can set the area bigger to get softer raytraced shadows...

[andrew trask]

snorry : misunderstood
why dont you use the "target area light" and set the web to your ies file ?
then you can set the area bigger to get softer raytraced shadows...

ahHA! yes, that works! I didnt realize that you can give any photometric light IES distribution. I was i-dropping the lights straight from Erco. There are still some small harsh shadows in the corner of the room right under the chair rail that look wierd, but mabey thats how it would look in reality. :shrug:

the rendering time took a pretty big hit, but I'm sure once I've messed with the shadow sampling it will get better. To get the most accurate results, should I set the shadow area to the size of the actual can light (i.e. 4")?

thanks joske!