Cineversity

Hi,
I been trying different setups for almost a week now with no success rendering a animation with GI and hair render.
The scene has a plane with a grass tag and a tennis ball with a grass tag too. There are no flickering in shadows or lights on the rest of the objects on the scene but the grass is driving me crazy, lot of flickering.

I’m using QMC as primary, and Light mapping as secondary method. Hair render I tried in root, vertex and pixel, with a GI quality up to 400% , but not acceptable results yet.

Render times are already huge, like 1 hour per frame or even more. it’s a 90 Frames animation so I’m searching for a flicker free setting with not more than 1 hour per frame.

when disabling GI the render has no flickering at all. but this is one of those scenes where GI is a must.

I appreciate any tips, thank you very much

Hi MP,

Can you create a mini scene, with the bare minimum that reproduce that problem. Really small!

How is it without Grass Tag/Shader? Same problem? (Help Content>Hair>GI can be applied but will not affect other objects.The Grass color has no influence to the environment via GI. The only effect that I can see is that the covering effect is taking the intensity of the reflection down.

Perhaps having dummy objects (invisible for camera but not for GI) with a surface color close to the Hair-content, and exclude any HAIR/Grass from GI might anyway the way to go, to get the colored light from those areas.

All the best

Sassi

Hi Sassi, once again thank you so much for your reply.

last night I render the scene with GI but on grass objects I add a composition tag excluding GI on those object. the result is flickering anyway. so right now I’m very confuse, I don’t understand why is flickering if GI is off for grass.

this is the first render with full GI+light mapping all objects with GI
http://www.triadstudio.tv/ftp/Grass_flicker_GI.mp4

this is a render of only 2 frames in loop (frame 1 and 2) without GI on grass objects but still flicker a lot
http://www.triadstudio.tv/ftp/Grass_without_GI.mp4

here a reduce scene
http://www.triadstudio.tv/ftp/Grass_flickering.zip

thanks

Hi MP,

Thanks a lot for the detailed preparation of the problem, very nice and supportive! :o) So I like to share any thought—I hope I do not got too far then. If—sorry.

I have made many tests, in Standard, Physical and—yes—in GI. What I have done is to throw out the “HDR Studio Lights” and used a simple light, and switched the Ambient Occlusion off. All of that is not the source of the problem. BTW rendering Gi contains “real” AO already. Ambient Occlusion when it is based on geometry was a way to fake GI roughly a decade ago. But that is your artist-call to quasi double it, and increase the render-time in that way. Just my two cents. IF your aesthetic builds up on it, use it of course.

Anyway, in the moment I deleted two of the three “Grass-Tags” on a single object and set the Anti-Alias for the Grass in the Hair setting to, e.g., BEST, the flickering is gone. If I stayed in the Standard rendering I used to set the default AA, not max2x2. Using the camera move, I would more tend to use motion-blur than to explore other options—if needed at all.

If possible, consider to render the Grass and anything else in separate passes, just a though, not knowing your complete project though.

If you encounter problems, perhaps the support has some ideas. I can’t reproduce problems with Anti Alias set to best.

Good Luck with the project

Sassi

Sassi, Thanks !!!

Glad you found what was the cause, I was adding 3 grass tags because i couldn’t find a way to fill the plane. so I decided to add 3 tags short, medium and long hair size.
I will make some new test with just one tag and I’ll try to render them separate.

I really appreciate you took the time to make some test, I did lot of test but never thought about the duplicate grass tags.
Thank you so much!

PS: I didn’t know that GI was creating AO by its own, I usually don’t use AO when rendering with GI because it was too much.
to be honest I still have lot to learn about settings, thanks for explain that

Hey MP,

Thanks for taking my point of view positively :o) 

AO in the old days was created by the geometry and how the polygons where facing each other. In that way, the Light occlusion showed up (dark areas) even if a light was very close by. It is a mainstream effect as it supports the believability. I see it more often overdone and once the audience become sensitive about, it might fail completely.

In GI the Ambient-(Light) Occlusion is part of the calculation and I guess people like the effect. I guess like most effects it might be worn out soon, as it is more and more overused. Again—my two cents.

I haven’t tested three (or two) Tags as going through the series of animations took a while already. It would be nice to have an option to set the length of the Grass via texture/shader. Perhaps some people create a suggestion at the MAXON website.

There is always something new, and the learning might never stop. As I normally have started my hands on classes with a presentation that we have more than thousand options and functions (etc) in C4D: If combined only one with another one each time, we have already way over a million possibilities. Combine three or more and it is impossible to know all dependencies nor problems. So, I have to dig into the use of several Grass Tags myself before I can tell anything. Perhaps it is not a problem at all. But then again, the combinations in rendering and how Grass is set up for rendering E.g., Raster vs Raytrace etc creates a wide variety of options as well. Etc. etc. etc.

What I tried to say was, every day something new happens with C4D for sure, and exploring the situation and creating your own Problem-Solving strategy is certainly a key element in you skill set.

Have fun exploring!

Sassi