Speed up Radiosity?

[handige_harrie]

Did you only try the default settings? How can you compare rendering speed if you don't know optimum settings?

As far as I know C4D has one of the fastest radiosity renderers (based on an old finalRender engine).

Anyway there have been a number of radiosity related topics lately.

http://www.cgtalk.com/showthread.php?s=&threadid=56226
http://www.cgtalk.com/showthread.php?s=&threadid=56235
http://www.cgtalk.com/showthread.php?s=&threadid=55439
http://www.cgtalk.com/showthread.php?s=&threadid=53611
http://www.cgtalk.com/showthread.php?s=&threadid=54080
http://www.cgtalk.com/showthread.php?s=&threadid=51806

And of course, MV radiosity tutorial:
http://www.mvpny.com/RadTutMV/RadiosityTut1MV.html

That'll keep you busy :p

[Buhrmi]

I've tried the default settings and i turned the accuracy to 0%. and still the rendering process of the "dottet" (prepass?) image takes longer than a equivalent render in MentalRay in higher resolution and better image quality. But okay, I'll have a look at the other topics. Thank you =)

[ThirdEye]

C4D is faster than Mray at calculating the GI solution, i've made some tests with a friend who owns XSI using optimized settings on both the apps.

[Per-Anders]

you need to know what the settings mean.

accuracy with c4d only refers to the balance (bias) between the Max and Min settings. man and min afect the number of sample "dots" that you see, max is the ammount close to creases and min is the ammount further out on flat surfaces.

samples refers to the number of random samples taken for each one of those dots, the higher the number the more accurate the brightness of that dot will be.

and you may also have multiple bounces (difuse depth) switched on.

now beyond these settings we also have to deal with the materials you use.

for instance if you were to have reflections or transparent materials with a higer ior these two tyes of material are killers for speed, with or without radiosity, but particually with, and that's the same with all apps. if you were to then add something like a bit of dispersion into that you're looking at ridiculously long render times with radiosity.

now, if you have a scene without reflection or refractions (or with the reflective and refractive materials/object gi emit/recieve turned off) you should expect to get some pretty good render times, faster than MR for sure (our render engine is based on Final Render technology).

so, maybe depending on how complex your scene is, try these settings:

accuracy 70%
diffuse depth 1
samples 600
min 3
max 20

you should get some much more satisfactory results. if not, then try lowering samples, min and max.

[ThirdEye]

Don't forget that in Mental Ray the final gathering is able to calculate only one bounce.

[Buhrmi]

Thanks for the replies. You've been right, I didn't experiment enough with the settings for radiosity. Now it renders quite fast. I think it was somehow a shock for me to see rendering taking fu**** long time with the wrong settings. Okay thanks again :)

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