Camera position creates splotches!!!

[DaForce]

Ok, I have been trying to create this
http://www.retromodern.com/images/lexon_7003.jpg

And its has all gone pretty well, how could it not given its a pretty damn simple model.

But i have been doing some test renders and i have been getting weird splotches. Initially i though it was just not high enough settings so i increased but that just made things worse.

One way i found to fix the problem is to lower the secondary bounces subs and depth, and if i increase it they return.
Now i noticed that after putting it onto the high settings (where it normally renders blotchy) and i move the camera a little from its current position it renders fine......what is going on.

I have even re-modelled the box and re-did the inside chamfering to make sure there was no problems, infact it was doing it before i even started chamfering the inside.

The thing i noticed was that the red material made the blotches look worse. But when either the 2nd bounce settings where lowered or the camera was moved the problem went away no matter what the material was.

The materials are
Outer beige, is a simple vray material with medium reflective, a touch of glossies, fresnel ticked and IOR of 2.0
Inner red is just a vray material with the diffuse change to a red color

Now some renders.

Clean render settings
http://www.apex.net.au/~daforce/vray/settings-clean.jpg

Blotchy render settings
http://www.apex.net.au/~daforce/vray...gs-blotchy.jpg

Now some different material tests to see if it was a materials problem

All materials
http://www.apex.net.au/~daforce/vray...ials-clean.jpg
http://www.apex.net.au/~daforce/vray...ls-blotchy.jpg

Outer beige material
http://www.apex.net.au/~daforce/vray/cream-clean.jpg
http://www.apex.net.au/~daforce/vray/cream-blotchy.jpg

Inner red material
http://www.apex.net.au/~daforce/vray/red-clean.jpg
http://www.apex.net.au/~daforce/vray/red-blotchy.jpg

Grey Vray Material
http://www.apex.net.au/~daforce/vray...ymtl-clean.jpg
http://www.apex.net.au/~daforce/vray...tl-blotchy.jpg

And finally the camera move test.

Original position, which causes blotches with higher 2nd bounce settings.
http://www.apex.net.au/~daforce/vray...aposition1.jpg

And the slightly moved position, where the exact settings where used as in the above original position but just the camera was moved a little.
http://www.apex.net.au/~daforce/vray...aposition2.jpg

Render/lighting environment was from this thread.
http://www.chaoticdimension.com/foru...er=asc&start=0

Any ideas peoples? As the solutions i have found are not a good enough solution. As it doesnt explain why its doing it in the first place.

also i more thing you will notice that on the material tests, that with the plain beige render and the grey render the difference between the clean and blotchy is minimal, but you can see a blackening in the back right hand corner on the blotchy settings so something is making it look bad....but what. And how could a simple red material cause so much problems, and why is it fix by slightly moving the camera or lowing the 2nd bounce settings.....and why we are at it...what is the meaning of life??

[vlado]

If your red material has its red component set to 255, try lowering that and see if it helps.

Best regards,
Vlado

[DaForce]

R = 204
G = 72
B = 50

Any other ideas?

Even if it was the R at 255 then changing the camera wouldnt make any difference would it?

[DaForce]

Ahh also im using 1.09.03R

Any else got any ideas?

[olivierfR]

hey... maybe "check sample visibilty" ???
cheers
olivierfR

[cocolas]

do you have any camera adjustment modefier to your camera??

that's also been known to cause issues.....

also I don't know if this will help, but here's a quite old tread Metin put together a while back that might help.....


http://www.chaoticdimension.com/foru...t=3851&start=0

also, once I had the same problems, in a scene w/ some glass in it....I doubled the "max transp levels" to 100 and the sploches (that were all over the image, nt just the glass) went away......might be worth a try.


paul.

[dbuchhofer]

I've run into this a few times, i think the most usual culprit was an animated camera, where the camera was animated with the 'Set Key' instead of the 'Auto Key' because set key created a HUGE list of alternate keys that weren't needed.

Why this would cause blotching i haven't a clue never really tracked it down far enough to be useful.

[DaForce]

olivierfR:
Thanks, but it didnt make any difference

cocolas:
Nope, i dont.
I am about to try a few things from that thread and see how it goes.
Thanks.

dbuchhofer:
Well, the camera isnt animated at all. So i guess that wipes that out.
Cheers.

[DaForce]

Ok, i changed the QMC sampler parameters (lower noise threshold, lower early termnation amount, higher min. samples) as instructed by vlado in the splotches thread.

But it made the render times 4 times longer, which isnt really acceptable. It went from under 10mins with IR calc to over 40mins with IR calc. I will fine tune the QMC sampler parameters and hopefully get it back down to close to what it was.

Here is the render.
http://www.apex.net.au/~daforce/vray/box-qmc-clean.jpg

Vlado, if you see this can you explain why it fixed it.

[cocolas]

yeah, that looks much better, but for 40 minutes....it is kinda high.....good luck and keep us posted.


paul.

[DaForce]

Thanks Paul

Will do

[DaForce]

ok,

Change the settings very slightly. lowered the noise threshold to 0.008 and the early termination amount to 0.8 and raised the min samples to 15 (i think) and it rendered in 12mins. (these changes were made from teh default values of 0.01 , 1.0 , & 10 respectively)
Much better now. Could probably get the time even lower but cant be stuffed. Need to finished of the model and stuff.

Thanks for all your help.

Weird problem but we got it sorted....kinda....

ooo yeah here is the 12min render
http://www.apex.net.au/~daforce/vray...c-clean12m.jpg