Generate / Recieve GI

[Matt Sugden]

I have some animation frames I'm rendering, essentially I have a massive yellow steel frame around a concrete construction, but as the animation progresses the steel frame becomes see through, so you can see the details of the internal construction.

 

I have done this by altering the refraction amount in the material, and set the IOR to 1.0, however this has had a big knock on effect to rendering times. what were 3-5min frames are now taking 22-30mins. Which is annoying.

 

The reason for this is the GI calc taking ages, on the intricate steel frame specifically, so I have tried switching the Generate Recieve GI, off and suddenly great render times are back, but my steel frame is not rendering with any colour.

 

I maybe missing something obvious here, but I assumed switching the Generate Recieve GI off would just switch off the soft shadows rather than removing all colour from the steel frame, Any help with this. I've attached a couple of pics, one without GI and the other with.

Edited November 19, 2009 by Bewdy

[John Dollus]

turning off receive GI is pretty much removing the light from affecting that object. would be better to render in two passes and composite.

Generate GI is usually the big time hit though so if you must render the whole thing in one go, try only unchecking that and compare your render times

Edited November 19, 2009 by John Dollus

[Crazy Homeless Guy]

Two passes would be a good solution. If you are using Max/MentalRay, which is sounds like you are, you may also want to try ticking the "Thin-walled" option under the Advanced Rendering Options roll out.