Author Topic: Animated Light Material renders weird in different frames  (Read 1547 times)

2022-04-01, 18:23:58

Börje

  • Active Users
  • **
  • Posts: 41
    • View Profile
Hello,

I have a strange behaviour which I cannot explain to myself:
I have made a simple Animation of sweep nurbs (circle along a spline) which grow with increasing time. There are two sweeps: one with a smaller circle which runs a little bit ahead. This one has a simple Corona Physical Material, light blue with a 50% opacity. The other one has a little larger circle and runs a little bit behind the other one. This ha a light material with animated emission and animated opacity.

Now on my 475 frame animation there are some frames on which the light material behaves diffenrently and I cannot say why. On some frames the rendered light material seems to have less opacity and then on the next frame it is normal again. Definitely on these frames there is no animated keyframe or anything similar. This results in the animation to flicker on some frames. Strange is, that its seems to affect only some of the Sweeps on different frames. I have put  different sweeps in one group and habve assigned the material to the group. So I would think that all sweeps should act the same and have the "flickering" on the same frame. But it's not so.

I have attached an example where there are three consecutive frames. On frame 322 everything is fine, on frame 323 one can see that through the light material you recognize the thinner sweep, on frame 324 everything is fine again.

When I copy those two sweeps into a new C4D-file it's still the same: on frame 322 and 324 everything is fine, on frame 323 the inner sweep shines through.

I also have attached those two C4D-scenes.

I use Corona Renderer Version 8 Daily Build RC 3, but didn't check if on Version 7 it's also like that.
Rendered it on Cinema 4D R25 117

Would be happy if someone could help.

Cheers

Börje

2022-04-01, 18:59:13
Reply #1

TomG

  • Administrator
  • Active Users
  • *****
  • Posts: 5434
    • View Profile
Checking the single spline version, though I can't tell you the why, it seems like enabling "Emit on both sides" in the Light Material will prevent frames 323 and 375 from looking different.
Tom Grimes | chaos-corona.com
Product Manager | contact us

2022-04-01, 19:44:45
Reply #2

Börje

  • Active Users
  • **
  • Posts: 41
    • View Profile
Thanks.

I will try it on a fast animation-test-render with the multiple sweeps.
But a first test told me, too, that emit on both sides makes the difference.

Nevertheless I suppose, this is a bug in some way!?


2022-04-01, 21:51:59
Reply #3

TomG

  • Administrator
  • Active Users
  • *****
  • Posts: 5434
    • View Profile
Don't know - it's entirely possible something in C4D has flipped the normals of the shape at some points during the animation, making making the geo of the spline inside out or something, which would make it a C4D bug I guess, but I don't know how to analyze the geo of the resulting spline to find out, maybe some close up look at it using a normal non-light material or using the curvature map could reveal what is going on :)
Tom Grimes | chaos-corona.com
Product Manager | contact us

2022-04-01, 22:44:33
Reply #4

TomG

  • Administrator
  • Active Users
  • *****
  • Posts: 5434
    • View Profile
This appears to be what is happening - apply a Phys Mat in place of the Light Mat, plugin the curvature, and add a light to the scene - the curvature map flips in those scenes, implying that the geometry that C4D is creating is inverted for some reason in those frames. I suspect that is not a Corona thing. It's not inverted normals though, as if everything looks as expected (not inverted in any way) if I don't use a Curvature map.

Tom Grimes | chaos-corona.com
Product Manager | contact us

2022-04-02, 11:42:57
Reply #5

Börje

  • Active Users
  • **
  • Posts: 41
    • View Profile
OK. Thanks for the explanation. Though pretty weird. I'm gonnna send this to Maxon.

Thanks again for your solution. It worked in my animation using "emit on both sides". Actually now it looks even more how it was supposed to look :-)

Cheers

Börje