I am new to Houdini and I am experimenting with the lighting. It seems quite complex, with many things quite apparent in other packages being present but buried quite deep.

At the moment I am experimenting with shadow maps. I have managed to get a shadow map written out for a test scene but I am unsure of some things.

1. What image format should I use for my shadow maps? Will any do or is there a special format? I have been using tif.

2. Please see my attached shadow map. Can anyone tell me how I can improve the quality with regards to the stepping in the shadow map? I have tried upping the shadow map res and increasing depth map samples but they are still present.

Thanks.

1. Use ‘rat’ format, it's the format of choice for Houdini maps(just call it my_map_name.rat).

2. Image didn't come through here - possibly too large for posting? Remember that shadow maps indicate *distance from light* - they aren't necessarily supposed to be pretty. To get smooth results in the final render, increase the sampling to get a soft edge. Part of your problem is that you're likely writing out 8 bit tiffs - not enough information in those for what you're doing. ‘rat’ will address that.

Cheers,

J.C.

Thanks man, I remember reading about .rat…

My shadow map is still stepping, I thought this was why my shadow in my image had noise in it but I'm not sure. Is it right that ‘Z depth samples’ is only used by Renderman?

If rendering in mantra, what are the most important setting for high quality shadows if z depth samples is only for Rednerman?

Thanks for the tips.

If you are getting stepping with your shadow map then you can:

- Increase the Pixel Samples to 2 x 2
- tighten the Near and Far Clipping planes such that the values are just large enough to encompass your scene plus a few units.
- increase the resolution of the shadow map
- add some shadow blur to soften the stepping and increase shadow quality to 2
- looking through the light tighten up the light's field of view through the use of focal length or aperture.

The default size for a shadow maps is too small, at least in a scenes where light keeps distance to an objects for 5-10 units. I always start from setting it to 1Kx1K and samples on 3x3 - the only way I found deep shadows work correctly without artifacts… after that they work just great, so maybe default size should be changed or something..?


cheers,
sy.

I don't use shadow maps all that often, so it's been a while since I fired it up, but in looking at it in a default setup, yes, I think you're right. Certainly just doing the basic setup, the shadow looks ratty. I fiddled with it, and it reads just plain wrong. Upping the res helps, but it doesn't respond to shadow softness, etc. It's possible shaders aren't hooked up correctly in the last few builds, someone from SESI should take a boo. The behaviour is in today's build too. Certainly it doesn't behave like you would expect.

Cheers,

J.C.

Did I have an illusion or there used to be here a post with H8 & H9 deep shadow maps comparison showing some problems in H9?

sy.

It was yanked, there was a flaw in the logic. Nope, no illusions.

Cheers,

J.C.

I was just wondering SESI's opinion on this but, hmm… afraid to dig further, if so :roll: At least I'm mentally sound

thanks!

Cheers,
sy.