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3D model flickering in Fusion. How to Fix?

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John Laggal

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3D model flickering in Fusion. How to Fix?

PostSat Sep 07, 2019 2:27 pm

Hello!! I have a 3D model that I imported into fusion in davinci resolve. When ever it moves, or the camera moves, it flickers:
https://www.dropbox.com/s/twwlfkh4dkrb4 ... y.mov?dl=0
How do you fix this? It was made in blender, and did not have this problem in bender...
Thanks!
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Bryan Ray

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Re: 3D model flickering in Fusion. How to Fix?

PostSat Sep 07, 2019 2:43 pm

This usually happens when there are co-located faces. Surfaces that are in the same spot, or even too close together, depending on the scale of the scene, will do this.

Without seeing the actual nodes, it's hard to diagnose, but check to be sure that your geometry is only coming into the scene once—it's not being added in two different Merge3Ds or twice in the same Merge3D—and that you don't have any duplicated shape nodes. I've occasionally had an FBX that somehow had all the geometry in it twice, and the solution was to just delete the duplicated nodes. Of course, in a very large and complex model, that can be a real pain.

One other possibility, now that I think of it, is that the export might have interpreted double-sided polys as two pieces of geo with their normals pointed in opposite directions. You might be able to solve the problem simply by culling the back face of all polygons. Use an Override3D node after the Merge3D that combines the object, and set the flags for Do Cull Back Face and Cull Back Face. If that works, you'll still have twice as much geo as you actually need, which will slow things down, but the tradeoff of render time vs. artist time might be worth it.
Bryan Ray
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http://www.musevfx.com
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John Laggal

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Re: 3D model flickering in Fusion. How to Fix?

PostSat Sep 07, 2019 2:46 pm

Ok. I'll try it.
Thanks!! :D
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John Laggal

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Re: 3D model flickering in Fusion. How to Fix?

PostSat Sep 07, 2019 3:31 pm

Hey Bryan, I tried it: https://www.dropbox.com/s/ek0ne39yr7pd2 ... 0.mov?dl=0
Can you give me some insight on this?
Thanks!!
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Bryan Ray

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Re: 3D model flickering in Fusion. How to Fix?

PostSun Sep 08, 2019 3:10 pm

Cull Back Face! You've turned off all of the polygons that face outward, leaving only the internal structure.

Now that I see more details of the model, I think there might actually just be a scale problem. I'm not willing to say that for sure, but you have a lot of polys very close together, and floating point numbers can get imprecise when they get very small or very large. In the two Merge3Ds right before the renderers, increase the Scale to 100. That will move all of the pieces further away from one another, allowing the renderers to more easily determine which polygon is supposed to be in front when they're very close together.

Culling the back face might still be necessary, but give it a try with and without it to see what happens.

You also asked for tips on getting a more realistic-looking render. First, once you get the forward-facing polys turned back on, you should see the texture properly, and that will help a lot. You may also want to give it a Reflect, particularly if you plan to show a bright object behind it with a low angle like that—as a surface becomes more parallel to the camera, its reflectance increases. Even very rough surfaces can become almost mirror-like at a shallow enough angle—that's what causes a mirage on asphalt.

Vito LaManna has some great tutorials on look dev and lighting in Fusion. His Patreon is definitely worth it.
https://www.con-fusion.net/home
Bryan Ray
http://www.bryanray.name
http://www.musevfx.com
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Mario Kalogjera

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Re: 3D model flickering in Fusion. How to Fix?

PostSun Sep 08, 2019 4:43 pm

Can't access the linked files but adding "replace normals" node fixes glitching from imported animated 3D geometry for me.

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