GI Compositing

[Randy Johnson]

I think you are going to have render each aspect out seperate or at least of different passses and comp them in another application where you can adjust them a little finer.

/randy

[Adam Trachtenberg]

The easiest way to do it is to use the free shadow catcher plugin, which you can get here: https://www.grafxflow.co.uk/forum_downloads/shadowcatcher.zip

Once you drop the .cob file in your plugins directory, you’ll see shadow catcher in your material>plugins menu. Put that in your material’s diffusion channel and it will catch GI shadows without messing up the background composite.

[Tony Spark]

I’m stuck in a similar space trying to nail camera projection, insert 3d (in my case cars), and use GI to illuminate the whole thing. Works fine on rendering stills but falls apart when you animate. The shadows become awful and the cars don’t “sit” in the scene. I upped all the render settings(30 hours for 160 frames) and, while better, still was unconvincing. I’m now playing with light domes but they mess with the car paint and still don’t convince me.
I’ve read here and there that animation and GI are not the best of friends in C4d. I’m wondering if Vray has this one licked. The possibilities of camera projection are stunning but not if the “flickering” and muddy shadows are the result of GI and an animated scene.

If anybody knows a fix for this I would be hugely grateful.

Tony

[Adam Trachtenberg]

IMO VRAy is better when it comes to GI animation, but you should be able to get a good result with AR … given enough time and/or rendering horsepower. Even with VRay, rendering GI animation is not what you’d call snappy.

What are your GI settings, output size, and what are you using to render?

[Tony Spark]

Thanks for getting back, Adam. This is killing me. The stills look great and the animation …”booty”.
It’s essentially a car animation set on a large panorama setting (1800X576). Road going off into the distance. The car goes down the road. With GI (I’ve put the same photo of the background in the sky as a fake HDR to get the paint working right) the car sits correctly on the road. But not once it’s animated. The shadow gets blotchy and isn’t under the car, and leaves dark streaks where it was. Similar results with a “sound stage” set with the car driving around using arrrayed lights. Looks fine in stills but weird artifacts in animation and in the paint.

The last animation of about 160 frames took 30 hours with GI settings:
IR+QMC Camera Animation / diffuse depth 2 / Stochastic Samples-high / Record density Medium / Smoothing medium and oversamling medium. Anti aliasing-best with Sinc filter. What’s strange is that the stills were only about a minute each, but in animation it went up to almost 12 minute per frame.

I appreciate any ideas/suggestions you might have. I have about twenty of these that I could slam out if I can make them convincing.

Thanks.

[Adam Trachtenberg]

Are the cars moving? If so you can’t use camera animation mode; that’s just for scenes where nothing is moving but the camera. That could be your problem right there.

[Tony Spark]

Thanks Adam for keeping up with this.
Both camera and cars are moving. The camera in a slow camera projection dolly and the car going down the road.

So which mode is best? I’ve tried the full animation mode on a previous test and the same thing happened with a huge hit on render time. In other tests I’ve gotten flickering on leaves, in the car paint, on all reflective surfaces and have been hearing/seeing that this seems to be an issue with C4d and GI in animation. But so far no solutions, other than getting away from GI in animation altogether. Seems a shame, because otherwise C4d rocks. I was hearing that Vray was solving these issues, but after your post I’m less optimistic.

Last night I faked a GI with a huge area light and an omni attached to the car. I was OK, but nothing as good as GI with the stills.

I remain hopeful that you or somebody have some magic bullet here that I’ve been missing.

Vimeo link https://vimeo.com/9860546 to see, roughly, the problem.

Thanks.

[Nathan Clark]

Randy:
I will indeed be using multiple passes and composite them in nuke.

Adam:
The shadowcatcher plugin seems to be getting me where i need to be, but it add a HUGE overhead to render times- at this stage I can live with that but I need some more advice.
Assuming my scene is as simple as a box on a plane:
I need the box and its GI shadows rendered with an alpha channel,
So the plane becomes invisible except for the effects of the GI
Could you advise as to the best method for doing this?, I have now installed the shadowcatcher plugin and tried to work it out, but cannot seem to get the result.
Thanks a lot
Nathan

On Point Cloud Nine

[Anthony Giola]

Make a light array. If you do it right then you should be able to receive convincing results. Go watch Andrew Kramers tutorial. he uses VRay on some of them. Its in 3DS MAX but you should be able to replicate it in C4D. GI is NOT good for animation. The light array will also render much quicker.

[Tony Spark]

Thanks Anthony.

That’s essentially what the second solution I put up is but I used an area light and added a little direction with a spot that was attached to the car. It’s OK but not as nice as the GI stills.https://vimeo.com/9860546Here also there’s a little flickering of the shadow which I don’t understand since there’s no GI at all. These are just tests but I would love to start getting this into our production schedule in lieu of old running footage that is now drying up.

I’m still not sure why GI isn’t a good solution in animation in C4d when it works so well in stills. Most of the architectural stuff I’ve seen is peppered with it and, of course, the 3rd and the 7th (https://www.thirdseventh.com/index.php?/4thdimension/film/) Clearly it’s being used to give that ultra real feel that I can’t seem to get with lighting.

By the way I couldn’t find Kramer’s tutorial. A lot of AFX stuff but no 3d. I’m pursuing solutions to this like a starved dog so if you have a link, please let me have it.