raytraced artifacts in displacement

[90okm]

Hi !

it seems like yet another topic about displacement artifacts, but i still can not find solution

here is the object. It is shaded with simple shader, which produces single SSS pass color only and noise displacement

in this render raytrace shading is turned on

as you can see it has awful artifacts (pointed with red arrows). wthatever i do i can not get rid of them

Displacement bound is ok

Z-importance does not affect right way

here is render with raytrace shading turned off

seems much worse

than i tried to render as subdivision

artifacts are still there though it changed its position

when i disable displacement everything seems to be ok

what shoud i do to eliminate this artifacts ?

re-dicind does not help

other manupulation on SOP level (fuse, facet) also has no effects....

i'm in impasse.....

PS houdini biuld 12.1.33

Edited December 27, 2012 by 90okm

[shushu]

convert sop: convert nurbs?

or phrps this: http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=3119&highlight=displacement+bounds

or

There is a mountain of information on the subject.

Edited December 27, 2012 by shushu

[Fabiano Berlim]

Well, mantra surface already comes with displacement bounds to grow accordingly with the displace size.

Older versions of Houdini use to have a bug in the shader, where sss was not taking the displacement in consideration.

What version of Houdini are you using?

Can you post the file?

[90okm]

convert sop: convert nurbs?

or phrps this: http://www.sidefx.co...lacement bounds

or

http://forums.odforc...lacement-bound/

There is a mountain of information on the subject.

I used displacement bound (look at my message again)

i know that there is a huge amount of info concerning disp bound... I wouldn't bother this forum with such simple issue

as the matter of fact disp bound does not affect artifacts which i described above

[90okm]

here is the scene

houdini 12.1.33

sss_rtraced.hipnc

Edited December 28, 2012 by 90okm

[Fabiano Berlim]

There are two problems with your iceberg geometry.

The normals coming from geometry is not right or at least not suitable for mantra. To fix it I put a facet node with pre-compute normals on.

The other problem is that your geometry is too uneven. Mantra and all micropolygon renderers are very sensitive, so try to avoid a mix of triangles and polygons, specially if they are too streched. The subdivide node can fix it smoothing the geometry.

Cheers!

sss_rtraced_fixed.hip

[90okm]

wow ! thank You so much !

i suspected that problem was in geometry, but didn't understand exactly in what

thanks !!!!!!!!!!!!!1