Author Topic: Cutaway Issues: (Fade Interference and ghost lines)  (Read 869 times)

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Offline Ryan Day

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Cutaway Issues: (Fade Interference and ghost lines)
« on: July 23, 2019, 09:49:25 pm »
I've been tearing my hair out for a couple days over this, and it seems it's the Cutaway feature causing the issue.

I'm working on an animation that has a few fade transitions in it. I've noticed several of the fades working sometimes and not others. Never thought to try with/without the cutaway to see if that was causing our problems, but I've just tried and it seems to be the culprit. I'm using the a cutaway feature to look inside a vehicle with a variety of different animations within. All of the fade animations don't work (pop from invisible to visible, or vice-versa, while the cutaway is active).

A second issue is that the objects that are exempt from the cutaway feature display witness lines either at the the intersection of the cutaway and that object, or at an intersection between the object and the other objects being cutaway. This happens regardless of which style of cap is used.

My Keyshot should be up to date I believe: version 8.2.8

I have to hit render on this Wednesday night, and these are serious issues. Any ideas?

« Last Edit: August 22, 2019, 04:18:15 pm by Bruno F »

Offline Eugen Fetsch

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Re: Cutaway Issues: (Fade Interference and ghost lines)
« Reply #1 on: July 23, 2019, 10:51:27 pm »
This is a known limitation - fade animations are not supported with cut away. 
https://luxion.atlassian.net/wiki/spaces/K8M/pages/431849563/Limitations+Known+Issues?showComments=true&showCommentArea=true

I don't know your project, so the only solution I see is to render two or even multiple animations (with and without the faded objects). Then you can fade them in post using the clown pass for masking.

Offline Ryan Day

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Re: Cutaway Issues: (Fade Interference and ghost lines)
« Reply #2 on: July 24, 2019, 08:16:51 am »
This is a known limitation - fade animations are not supported with cut away. 
https://luxion.atlassian.net/wiki/spaces/K8M/pages/431849563/Limitations+Known+Issues?showComments=true&showCommentArea=true

I don't know your project, so the only solution I see is to render two or even multiple animations (with and without the faded objects). Then you can fade them in post using the clown pass for masking.

Thanks for the info. That's extremely disappointing, and a significant limitation. I have several different fades at different times so I will have to set up several more things and render out several animations to get around this; and my day is already extremely full.

Online INNEO_MWo

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Re: Cutaway Issues: (Fade Interference and ghost lines)
« Reply #3 on: July 24, 2019, 01:27:15 pm »
Hello.

I did a small test with fade animations. The result was.
- fading an object that is effected by a cut material, the cut (or better the caps) will be fully visible by one single frame (just like a pop effect)
- the same fade animation applied on the cutaway material part solve this issue. (and if I think about it, it is completely logical)

And the cutaway has to deal with overlapping geometry (coplanar polys) in the same way as a fade animation does. So some tiny gaps (translations or scale) will always help.
Sometimes I remove the inner surfaces of one part (e.g. two cubes with the same size - one in front of the camera and the second behind the first one - the backside surface of the front cube use the same space with the front surface of the cube in the back - now I would try to remove the back surface of the front cube - there is no effect to the front cube if the camera doesn't see that the font cube is a "shell" and a fade animation looks good without any "Z fighting, weird lines or wrong shadow effect)

I know that this is no magic trick advice that help in this situation with a tight dead line - and I wish you all best for the results - perhaps you can keep this in mind for a similar project in the preparation phase?!


Hope that helps

Cheers
Marco

Offline Ryan Day

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Re: Cutaway Issues: (Fade Interference and ghost lines)
« Reply #4 on: July 24, 2019, 01:34:43 pm »
Hello.

I did a small test with fade animations. The result was.
- fading an object that is effected by a cut material, the cut (or better the caps) will be fully visible by one single frame (just like a pop effect)
- the same fade animation applied on the cutaway material part solve this issue. (and if I think about it, it is completely logical)

And the cutaway has to deal with overlapping geometry (coplanar polys) in the same way as a fade animation does. So some tiny gaps (translations or scale) will always help.
Sometimes I remove the inner surfaces of one part (e.g. two cubes with the same size - one in front of the camera and the second behind the first one - the backside surface of the front cube use the same space with the front surface of the cube in the back - now I would try to remove the back surface of the front cube - there is no effect to the front cube if the camera doesn't see that the font cube is a "shell" and a fade animation looks good without any "Z fighting, weird lines or wrong shadow effect)

I know that this is no magic trick advice that help in this situation with a tight dead line - and I wish you all best for the results - perhaps you can keep this in mind for a similar project in the preparation phase?!


Hope that helps

Cheers
Marco

Thanks for the tips; I'll keep that in mind for future projects. Unfortunately they don't help this specific case; the objects I'm fading in and out aren't coplanar with anything, they're just within (or partially within) the area of the cutaway object - in other words, intersecting it. The second issue (witness lines on other objects) is something a little more difficult to figure out, but it's a more circumstantial issue and I think I can work around it.

For this case, what I'm going to do is create a second version of the object being cutaway that is cut out in the same shape. Once the cutaway animation plays I'll hide the object being cut (and the cutaway body) and replace it with the actually modified version. So, as far as the program is concerned, the cutaway feature itself is only actually being used during the transition from full object to cutaway object. Then I'm free to fade in/out the objects within at my leisure without issue. Thankfully I'm just cutting away the object on a constant 30 degree angle, so it will be fairly easy to match up the animated cut with the permanently cut body.