View Full Version : MNodel that slows global illumination to a crawl.

07-19-2015, 04:37 AM
I was looking at a new figure to put in the London at night scene, instead of Daleks. And thought an exported Baphomet demon would work well,

But to my surprise, the render times went sky high, (I estimate a week for a halfway decent render). A few quick checks with options showed that radiosity was the factor making the difference, but I have no idea why this new model is so bad compared to the older ones. I tried final gather and monte carlo.

I include a screen shot with VPR on and some settings shown.

Does anyone have any ideas what factors in the model would make global illumination / radiosity so painfully difficult to process?

(I tried rebooting in case LW had got stuck)

LW 11.6


07-19-2015, 08:01 AM
What is Render Globals > Ray Recursion Limit?

If mesh is bad, ray bounces back and forth inside of geometry, couldn't escape it, like f.e. semi transparent skin, and always reaches ray recursion limit..
Check if mesh has double sides, whether it's open or closed mesh..
Merge points, unify polys, is LW showing that some where removed?

07-19-2015, 12:40 PM
Thanks for the suggestions, I found a few things to clean up, but nothing that major, though reducing the ray recursion limit helped.

One other thing I just noticed - while processing GI the busy levels are REALLY low, like it's only using one core.

07-19-2015, 01:00 PM
Maybe there is used node or shader, which is locking multi-tasking.. ?
Clean up surfaces to Default surface to see how much it changes results..

07-20-2015, 02:13 AM
Are you using the Material Mixer node? I had issues with this on a render I left running over the weekend, but I haven't managed to track down the exact circumstances yet.

07-20-2015, 12:35 PM
Thanks all - no clever shaders, it's all really simple.

I'm beginning to wonder if my PC is overheating and dialing itself back...

07-21-2015, 05:55 AM
Install SpeedFan and check in that case (if you use Windows) but I don't think that's the problem.

It's the rendering time that goes sky high ? not the GI preprocessing ?