limitiations of GI

[jackb602]

I'm posting to the General Discussions forum because I suspect the issue I'm describing affects people on a range of platforms. I model in FormZ and use Cinema 4D for texturing, lighting, and rendering.

 

One problem I consistently come up against is the ability to accurately show direct light (from the sun & sky) as well as bounced light in the same view. The two images attached here are an example of what I'm talking about.

 

http://www.cgarchitect.com/forum/filepush.asp?file=LandingDark.jpg

 

http://www.cgarchitect.com/forum/filepush.asp?file=landing.jpg

 

The staircase leads to a roof deck, and its enclosure at the level of the roof is mostly glass, so that light will filter down into the house. In the first image, I have lit the scene just with the sun, and have increased the radiosity strength as much as possible without blowing out the highlights. Nevertheless, the second floor (at the base of the staircase) is in dark shadow. In the second image, I have taken the rendering in to Photoshop and brightened those dark shadows using the Levels tool. This has worked reasonably well here (so far it's the best solution I've found) but the image already shows some banding on the wall to the right. This banding can be much worse when the shadows are boosted too far.

 

Overall I'm really impressed with the rendering capabilities of Cinema, but do other packages face the same problem? (Hmm, I suppose I could post a DXF file of this scene and let others have a go at it in other programs.)

 

Ironically, FormZ (a great modeler whose rendering engine drives my batty) has a postprocess feature called Exposure Correction. It works just like the Curves tool in Photoshop, only it deals with the full, unclamped range of light values in the rendering.

 

I realize that a scene like this in the real world would contain a HUGE range of light intensties, and I've started to think about manually creating an HDRI rendering (by assembling different "exposures" of the same scene) to allow for more accurate control in HDRshop or a similar app. I got the impression that Brazil can output HDRI images; is this correct? Do any other renderers have this capability? I suppose that would be a good solution. This still seems like a lot of work to simply show realistic lighting. I'm curious to hear how you all deal with similar situations, and I'd appreciate any feedback or suggestions.

 

Thanks,

Jack

[nisus]

(Hmm, I suppose I could post a DXF file of this scene and let others have a go at it in other programs.)

This sounds perfect for another unchallenge

 

nisus