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Simon Wicker
11-05-2006, 08:37 PM
I don't think I have seen this mentioned before so I thought I would pass on a little tip for rendering an animation using stochastic mode GI in a more efficient way.

Basically you can speed things up by letting Cinema combine as much work as possible into the scene motion blur post effect.

Set your AA to none, turn your GI settings to stochastic and set your samples down really low, 8 or below, with a diffuse depth of 1 and then make sure you set identical noise distribution off.

Activate scene motion blur and set it to 16 or 25 samples.

Now when you render your scene the scene motion blur gives you really nice blur, the camera offset gives you decent AA and because you get a different distribution of noise in each pass for the GI when the frames are blended you get a smooth result from the GI so that your 8 samples are mixed multiple times and you get the equivalent of a much higher sample rate.

Best of all this is really quick as you are not using any oversampling to get decent AA and you are not having to up the stochsatic samples too much to get a smooth result from the GI.

Using this technique I have been getting around 15 minutes a frame for a flyover over of sixteenth century London that I'm working on currently (rendered at widescreen pal res of 1024x576). I should point out that this scene is all diffuse and does not contain any relective or refractive surfaces so I don't know how this technique would work in a modern architectural setting although it should still be better than using a brute force method of high stochastic samples for decent GI quality.

cheers, simon w.

JoelOtron
11-05-2006, 09:04 PM
Thanks for the tip Simon--snipped. I was reading the new (to U.S.) 3D World--which goes through a tute using scene MB to fake a light dome (see my thread lower down). Although the results werent so great--I have been thinking ever since that maybe there are other ways to use it to blur/mix results per frame.

bunter
11-05-2006, 09:36 PM
thanks -neat idea :)

LucentDreams
11-05-2006, 10:26 PM
Just wanted to add use this same technique when using Ambient occlusion. This is how we rendered all the fleas in HP flea which had tonnes of seperate shells and such that needes that GI/AO look, we used a maximum of 40 samples minimim of 5 and used 50% accuracy. SMB was at 16 most of the time, and for some scenes with faster motions we used 25 just because a little banding became noticable at 16.

wesware
11-06-2006, 12:38 AM
I'm all for better and faster...thanks Simon.

AdamT
11-06-2006, 04:59 AM
Great tip, Simon! :adds to tip collection:

Zendorf
11-06-2006, 06:48 AM
Very clever production technique, thanks for sharing:thumbsup: Also sounds like a good way of smoothing out the graininess of AO...

feel3d
11-06-2006, 09:22 AM
Hi Simon, thanks for your great input! I'm testing the scene attached as a picture. When i want to make a animation form my scene it takes more than 2 houres to render one frame?
I have a MacPro 3Ghz coud core, so there must be something that i'm doing wrong here...?

lllab
11-06-2006, 10:38 AM
this long rendertime is due Ar has problems with GI + Relfective materials. simon pointed out this alraedy.

i guess this trick only works with non reflecting materials. glas metals etc like in archviz is not fast rendering in AR with gI on.

cheers
stefan

feel3d
11-06-2006, 11:00 AM
Thanks for your reply illab! I had a deep wish that it could be done...

lllab
11-06-2006, 11:14 AM
well there are solutions (3rd party renderengines) out there that render such a scene in minutes not hours...
cheers
stefan

feel3d
11-06-2006, 11:17 AM
well there are solutions (3rd party renderengines) out there that render such a scene in minutes not hours...
cheers
stefan


I hope you mean the Vrayforc4d plugin...!

moka.studio
11-06-2006, 11:29 AM
Hi Simon, thanks for your great input! I'm testing the scene attached as a picture. When i want to make a animation form my scene it takes more than 2 houres to render one frame?
I have a MacPro 3Ghz coud core, so there must be something that i'm doing wrong here...?

for a scene like this, you could use a non-gi lighting setup with materials, then render out an AO or stochastic pass with no materials, and glass surfaces turned off (maybe), then overlay the 2 in post and modify to suit. Should give some decent results.

rsquires
11-06-2006, 11:29 AM
I hope so too. Any news please Stefan. Can we expect anything for Christmas from Santa?

regards

rich

feel3d
11-06-2006, 11:35 AM
for a scene like this, you could use a non-gi lighting setup with materials, then render out an AO or stochastic pass with no materials, and glass surfaces turned off (maybe), then overlay the 2 in post and modify to suit. Should give some decent results.

Nice tip Moka! For a still my rendertimes are ok.

Simon Wicker
11-06-2006, 05:19 PM
Nice tip Moka! For a still my rendertimes are ok.

another thing you should do is to make sure that all your reflective, transparent or refractive materials are set to not generate or receive GI. these types of material do not influence the visual quality of the GI very much but they do create a huge number of extra rays as the GI has to trace all the extra rays for the reflections and transparencies.

by excluding these you are once again approaching a fully diffuse environment which will render most efficiently in AR.

cheers, simon w.

nutriman
11-07-2006, 10:01 PM
thanks for the valuable tip! :)

JamesMK
11-15-2006, 04:08 PM
Just popping in to say thanks for the tip, Simon. Just finished rendering a seven second shot at 640 x 360 using this trick. Had stochastic accuracy set to 60%, 6 samples, motionblur samples set to 16, and a fair amount of reflective surfaces (reflection depth at 1) - rendered in between 10 - 20 minutes per frame with a totally acceptable output quality.

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