Hi guys, I'm fairly new to Carrara so I hope there is a simple solution to this that I'm just not finding. I am using the new C4pro, although I had the same problem with C3. When I render using Global Illumination, I seem to get lots of grubby dirty looking artifacts. This really is quite annoying. I have played around with most render settings and havn't managed to cure it. Is this an inherant bug of am I just missing something? Any help would be most appreciated.. This pic shows what I mean.

Here is a pic of an actual work project for a client. The solid red white blue triangles are particularly poor. The sign on the top also has a couple of grubs on it. I have use the default HDRI trumpet scen as a base.

Have you tried to increase interpolation value or to turn it off? Also, you can increase the photon count to have a better result. -TOXE

agreed... also increase the lighting quality to 'excellent' or 'best' and you might have to reduce the accuracy down as low as 1 pixel in order to get the results you want.

Using the "Improved Edges" option will significantly help this. Engaging that option sometimes has better results than just the iterpolation or photon solutions.

yes Mark, but it don't work only with Indirect Light? Or there is a way to use it with simple GI?

Success! Thanks for the tips guys! I have ran a half dozen tests with various settings and the one that seems best is with Interpolation off and lighting quality set to Best, with lighting accuracy at 2 pixels. This gives a lovely result on my test piece. I seems that it renders much more quickly with Interpolation off, way faster. Anybody know what interpolation does and when it might be necessary to use it? Thanks for the help, Brian. By the way, I am a Rhino man for ever but I'm going to be using C4pro a lot as it now imports Rhino nurbs directly. Happy days ahead.

Interpolation is in there simply so you have to visit this forum. We sponsor it ever year! ;-)

Seriously, it is supposed to speed up rendering by using a caching mechanism to avoid recomputing the light for every pixel. This becomes more important if you are using indirect lighting.

Mark

Message edited on: 12/10/2004 11:00

Actually I got my times mixed up, it was seven mins with it on and eight with it off. See you all soon.

Interpolation seems to be more like a draft render mode. Setting to 100% seems better than leaving it at 20%. But turning if off entirely gives even better results (though it takes longer to render). Like all the Carrara render controls, it's ambiguous. The manual describes pretty much every render control as "Setting this control will control its setting".

The fact that it took you so many tries and you still weren't getting better results says a lot about the manual. Everyone here though has gone through the initiation process already. Welcome to the party.

Message edited on: 12/10/2004 18:15

Apologies for the delay in getting back. Work....

Toxe, your are correct about the Improved Edges only being available with Indirect Lighting. Using pure G.I. doesn't allow for it. However, as the image above shows, using Indirect Lighting with Improved Edges creates a nice image that is artifact free - at least in this example.

Interpolation: Ahhh, always the mystery. Interpolation accuracy (educated guessing) simply tells Carrara how "correct" you want its light calculation to be. At the default 20%, Carrara is only accurate on 20% of its calculations - the rest uses a close-is-good-enough approximation. Turning Interpolation up to 100% or turning it completely off means Carrara does all the math and calculations for the the light rays. Of course doing all that math takes longer.

On scenes with no transparent objects, the interpolation difference is not that great. On scenes with glass objects, these settings are the difference in completing the image in your lifetime or not!

Message edited on: 12/11/2004 16:13