occlusion:: different sampling pattern on every render

[sanostol]

Hi,

I'm not sure if it is good or bad, or doesn't matter, but i use a occlusion shader and every time I rerender the sampling pattern looks different. so every render lools slighly different. the more samples the less obvious it is, but my general question is, if this is normal or if there is a way to do it all the time the same

martin

[old school]

You may want to use the Edit Render Properties and add the jitter and jitter seed parms along with Dither.

Try setting the jitter and dither to 0 to see if that helps...

[sanostol]

Hi,

could not find jitter seed, but the rest did not solve it

You may want to use the Edit Render Properties and add the jitter and jitter seed parms along with Dither.

Try setting the jitter and dither to 0 to see if that helps...

[Jason]

You could use an Irradiance Cache (see Mantra ROP) and both improve render times (on re-renders) and get a better smoother result that also won't cache when you render again.

In production its not uncommon to render with anywhere between 256 and 1024 samples, just so you know - it's an expected artifact.

If you use PBR instead, there is a toggle on the Mantra ROP called "Sample Lock" which will use the same sampling pattern for every frame.

[rob]

I don't know if this tip will help you as I have never done it in Houdini . Depending on your requirement , bake out 1 frame of your occlusion with your object in a default position as a texture map then multiply it with your diffuse map. This will give you the occlusion look without the flicker.

So that does bring the question can you bake out lighting and occlusion as a texture map ?

Rob

[edward]

So that does bring the question can you bake out lighting and occlusion as a texture map?

ShaderUnwrapping

[stu]

I've never been a fan of baking the occlusion into a texture map. What you want to do is cache the irradiance in a neutral pose with a rest position.

[Jordan]

I've never been a fan of baking the occlusion into a texture map. What you want to do is cache the irradiance in a neutral pose with a rest position.

hi, stud. Can you further elaborate on the workflow of cach the irradiance in a neutral pose with rest position?

And also how to use point cloud to speed up occlusion?

thank you.

jordan.

[rob]

Stu , it would be awesome if you could go through your workflow ....

R

[v_m]

looks like simply using radiance cache can yield some seriously amazing results

just open the example available in the houdini help, create a mantra rop node, render one slow occlusion... and then go under the irradiance tab and enable irradiance. wow! with 256 sampling it rendered that teapot really fast and flicker-free (I tweaked the max-min pixels under irradiance to get clean results). it rendered fast with motion blur as well. and still fast with 100 polygonal teapots (some 160000 polygons) subdivided at rendertime

[stevenong]

It will be nice to look at some rendered images.

Cheers!

steven

[rob]

radiance caching works like a dream .....excuse the the jpeg / QT it was that or 19mgs. It renders pin perfect no flickering. To render out a sequence for the cache I used " $HIP/cachefiles/gifile.$F4.pmap " .

Unfortunately I cannot upload the scene file just yet but if people want I will knock up a 9.1 file. This also brings up another question concerning the use of the the second type of occlusion calculation we have in Mantra " void occlusion(float coverage&, vector missed_direction&, vector P, vector N) ". Is it possible to write the occlusion data out and read it back in , much like the radiance caching or somehow use a point cloud

Rob

teapotshot3.mov

Edited May 26, 2008 by rob