Gary Mc Ginty

We would like to composite an animation of a operating Theatre with moving people. At the moment its flickering even on high settings.

We got advice to use ambient occlusion to fake GI.

We know how to set up the ambients occulsion which we tried and it is working well.

what we dont know is what to use for the other passes?
we have tried to just turn off the GI but the results are not great. The rendered scenes were very dark.

Any idea of how to setup the other passes and what would be the best settings for the compositing?



thanks

nicnic

Your ambient occulusion pass is wrong. How are you doing it? It looks like a environment override something?

You need to use Render Elements Vray_ExtraTex with vray dirt as the map, adjusting the dirt parameters to suit your scene.

Then use multiply in post and adjust opacity to suit.

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Also, you shouldnt be getting flickering in that scene. Seeing as though you are compositing anyway why dont you do the people seperately using vray matte object?

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STRAT

yes, wrong AO pass method. in Cinema you give the complete scene a luminous white material and run AO over that.

also, your initial pass should be a standard beauty pass. i dont know what you've done there. AO is just an added overlay thats lightly comped over in post.

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Gary Mc Ginty

thank you for the fast reply.

We went through some AO tutorials saying we should use an override material with a Vraylight material and a VrayDirt inside. this is what we have done for the AO.
we can not find the render element Vray_ExtraTex, is this in Vray 1.50?


and could you please explain what to do for the first pass? we should not use the GI so we turned that off but then we have not got enough light in the scene.

and for using Vray matte shadow, the moving people sometimes get flickers, that is why we wanted to try it with AO.



thanks

Fran

Hi Gary,

Add a few omni lights around the scene that are set to ambient only. Then render your direct light/color pass so that it will look like what you have only it will relieve the dark areas. Then comp that with the A/O pass you've already done. In Photoshop, adjust the opacity and brightness of your AO layer until you like the results.

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- Fran
If you must reinvent the wheel, remember that it works best if it is, like, roundish.

crazy homeless guy

As Strat said, your base pass should be a standard GI beauty pass. AO is designed to enhance the GI pass, not replace it.

Using AO you should be able to use lower settings on your GI pass, therefore speeding it up, but still bring out some of the detail once you apply the AO pass.

I don't think your AO pass is as bad as what is being implied. You should still be able to get something decent out of it if you do a level adjustment on it in Photoshop.

Also, try applying the pass using Multiply instead of Overlay.

I attached the corrected AO pass in my attachment. Basically, you want the layer transfer mode set to multiply. Then, the areas that are white, or near white in the AO pass will not effect the image, but the areas that are dark will add detail to the image at the contact points, corners, or other places where there is darkness.

Attached Images

Untitled-1.jpg (24.4 KB, 42 views)

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travis schmiesing

nicnic

thats not an AO pass either.

it should basically be even black and white, with black on surfaces where they are closest to other surfaces, spreading to white on 'open' areas.

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RyanSpaulding

You cant fake GI by adding an AO pass to a non-GI render. To fake GI, you need to add lights on the bottom of the model...maybe a few and set them below the floor....then exclude the floor from casting shadows. That will get you closer to your desired result.

STRAT

yeah you can

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Mr-JosE

Its quite simple really. Make a 100% illuminated standard material, add a v-ray dirt map to the diffuse slot, and adjust the settings of the v-ray dirt map to suit. The occluded colour should be black (or any colour you want shadows) and the unoccluded colour should be white. Adjust the radius to control the spread of the AO pass. Nice and easy.

For your render settings; on the global switches rollout turn off everything in the lighting group. Use the new AO material in the override material slot.
And make sure GI is turned OFF.

Hit render and you will have your AO pass.

For you to use it as a replacement for GI you need to make a diffuse and a direct light pass using the render elements controls. Setup your scene as you would normally, without GI, and activate the vray_diffusefilter and vray_lighting filters.

Once rendered load them into PS. Make two groups, one for AO, and other for Lighting. In the AO group you should have your diffuse pass with the AO pass on top of it set to multiply blend mode. Set the groups blend mode to linear dodge (add). In the direct lighting group you have the diffuse pass with the direct lighting pass on top of it, with the blend mode set to multiply too. Place the AO group above the direct lighing group.

With this setup you can control how much 'GI' you have, tint the GI, tint the direct light etc, etc.

Hope this is clear.