Preventing AO artifacts in animation

Preventing AO artifacts in animation

I'm doing a project for work where I need to animate a scene that uses ambient occlusion. After doing a first animation, I noticed that the shadows started flickering and I had lost some texture detail. I turned "detail detection" on and then there were artifacts in the texture map.

Should I keep playing with the non-path tracing parameters (suggestions?), or switch the error level down to the level where path tracing kicks in? It's much slower, but the result seems artifact-free.

The type of shadows that flicker: https://www.dropbox.com/s/rfzc6nzjs0b8o8k/Screenshot 2014-08-29 08.10.52.png?dl=0

The type of artifacts I'm seeing:
https://www.dropbox.com/s/mil3oocbz4othyp/Screenshot 2014-08-29 08.11.27.png?dl=0 (right above the whale's nose in this frame, but they appear all over that texture at various times)

Edit: Here are my settings for the AO -- https://www.dropbox.com/s/e2zlabvf9iuce1r/Screenshot 2014-08-29 08.13.26.png?dl=0

Thanks!

This can be a bit of a can of worms. Of course, Reducing the "Error" setting on the Irradiance Cache portion of Ambient Occlusion will create improvement AND increase your render-time (I've experienced an increase 40x longer render with 0.0 Error setting).

You can also choose to increase your "Rmin" value - I've discoverd with an Rmin at 32 this will smooth out all the blotches and your render time is fast - BUT you won't have any detail shading - so your render may look flat. :frown:

There is a way to FAKE Ambient Occlusion with Area lights:

I personally opt for using a few Area Lights with Samples set between 7-16.
Usually one large area light directly above your scene - the size should be a bit larger than the scene. And then two lights at two angles illuminating the camera facing portion of the scene. Yes, each frame takes longer to render (about 16x longer in this case), BUT there are absolutely no blotchy artifacts.

For the renders below I used the "entrance hall Pano" - as you can see with Ambient Occlusion, it colors the scene with a bit of yellow and there are blotchy artifacts. The Area Light scene is clean and color balanced.

File included. Cheers.

Thanks, Rene. I changed to the area light solution and I'm getting much better results! Is there a way to keep the HDRI reflections but turn off the light-casting properties of the HDRI tag? I didn't want that so I turned off the HDRI tag entirely and added some gigantic white spheres with emissive textures to create reflections...makes the scene look a little funny

maruchan said:

Is there a way to keep the HDRI reflections but turn off the light-casting properties of the HDRI tag?

Click to expand...

The easiest way is to have an HDRI tag on your camera with NO Radiosity tag. Without a Radiosity tag the camera will not use any light information in the HDRI to illuminate the scene, but the image information will be used for reflections - check out my file, I do it that way in there. Cheers.

These are great tips as I always have all kinds of problems with artifacts when rendering. It probably has a lot to do with most of my renders containing very detailed complex objects with metal shaders applied. Will try some of these out to see how it helps. Right now I have to change settings that give long render times to get anything decent.

Thanks!

Thanks Rene!
Your set up sure makes a beautiful render.

My Best Regards
Jeanny

Thanks a bunch, Rene. You saved my bacon :icon_thumbup:

I am grateful that my suggestions help out. I've encountered the same problems with artifacts and have done literally many hundreds of renders trying to find the balance between a good render quality and modest render time. Perhaps I'll create a tutorial or workshop for Rendering. Cheetah can do some amazing things and I should pass on the tricks and insights I've learned. Cheers.

Thanks

I'm having the same issue, as you can see the flickering underneath objects, though I had taken best rendering.

you can see it here : http://youtu.be/KXb6wfmleSc

I'll try your trick and let you know..
Thanks for being on this forum.. :icon_thumbup:

great info! Thanks Rene66

anotherone said:

I'm having the same issue, as you can see the flickering underneath objects, though I had taken best rendering.

Click to expand...

Hey there - thanks for your comments. I looked at your video and can see that this is an Irradiance Cache issue. The good news: there is a way to get a solid render. The bad news: it will add to your render time.

I created a quick version of your set for my own test. To create a similar lighting effect I used five (5) area lights. One for each wall and one for the ceiling. I also made a slight adjustment to the camera and changed the Tolerance to: 0.03 to reduce the "grain."

Yes this will take longer to render - BUT - it is much shorter to render than changing the Rmin value on the Radiance Tag to 0.0

Attached a File to help out - Cheers

Wow

Goes to show you there no community like the Cheetah community! This part of the why I love Cheetah 3D. I continue to plug away and learning the tool. I learning a lot from all of you.


Thank you!

Great tips, Rene! Thanks!