I have some issues with my lighting (sibl), need some help.

[maze]

Hi there!

Well this is my first post in the mental images forum. I have some experience using mental ray but surely not as many very experienced users I've seen while lurking the forums. So hope to learn something from you!

Ok I am currently lighting a scene I modeled some time ago and I am facing some anti-aliasing/lighting artifacts problems in my test renders.

So yes I will like to achieve a smooth render..

Here is my test render image:

render-test-artifacts.jpg

and here a render test with a quick touchup in PS to give an idea of the mood I want to achieve. (hard sun hitting) with darker foreground.

mood-test.jpg

Also here is an image where you can see my scene and how the lights are positioned.

lighting-setup.jpg

and lastly an image showing my render settings (with a "hidden" question!)
difference.jpg


So then I guess my questions would be:

1) how can I get rid of those lighting artifacts to get a clean render. (this is intended to be a still frame, which I am thinking to transform into a moving matte painting.

2) In the render picture it shows, trace deph inside "indirect illumination" tab and also the "render" tab what is the difference between both? Is one more important than the other?

3) When I use the Sibl plugin I noticed that the images rendered look washed out until I disable the camera lens "Sibl lens node" that creates with the lighting rig. I have my gamma settings set to input/output (2.2) And I am not working with a comp package for this one. Only photoshop. Can someone please explain me this. I am not sure if I should leave the "sibl lens" and adjust gamma in PS or simply remove it.

4) I realized that then I add a portal light in front of the scene (in front of the Mr Sun) it does render as a "black square" does someone have any idea why is this?


5) I am having some confusing regarding IBL and mental ray. Is "Sibl" method from hdrlabs same
as IBL mode in mental ray? I saw an IBL tutorial from throsten hartmann and I am not sure
what is the correct approach to IBL I should be using in MR. Hope you can clarify me this blur.


I thank you in advanced for your help.

Hopefully I can get this issues clarified and keep working.

Regads.


-Manu

[cdog]

Hi,
I'll start with question 2. Trace depth in the renderer tab is a depth to which a ray is traced. (let's say depth of visibility). If you had several glass panes in a row these settings determine how many times a ray would go through them. After reaching the desired number of reflections/refractions it ignores all transparent objects in its way and continues till it reaches the first solid object and takes its color. So this setting affects eye, glossy, reflection/refraction rays. The settings in the Indirect illumination tab is similar but it affects only FG rays (those which are emmited from FG points). So basically it's again the depth for the indirect illumination to look. Similar setting is in GI with photons.
Ad 1 - you could try more samples in the shader which causes the fireflies. Optionally - these are probably reflections of some bright objects (maybe the sky portal)-so making it invisible could help. Or try unified sampling
Ad 3 - i'm not sure what the "sibl lens node" does, but i think if it works without it then go for it (just check in the environment slot that the HDR is loaded with correct gamma)
Ad 4 - just turn off Visible to renderer in Advanced parameters of the sky portal
Ad 5 - last time i checked sIBL it worked like this - it maps the HDR in the envinronment, using a rayswitcher it just uses multiple images - one for reflections, one for lighting, as a background. Then it adds a skylight which is set to use environment and optionally it puts mrSun in the place specified in the the editor which is rigged to the sphere (the sphere itself is just for the user to better visualize the position of the HDR in the scene). So the scene is lit with FG (which samples the environment thanks to skylight) and for better and crispier shadows the mrSun is used.
The IBL mode in MR is different. It basically needs just the HDR in the environment to light the scene (something like iRay). Its shadows are crisp enough so you don't need anything else.