Animated Displacement map causing exaggerated effect?

# 1 16-01-2013 , 04:12 AM

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Animated Displacement map causing exaggerated effect?

Hi folks! I've been lucky enough to get answers from this forum in the past, hopefully someone can help me with this one...

I have a setup for a tunnel animation using a cone and an animated displacement map. The UV map for the cone is created so that the tapered tip is in the center, and the wider top end is the outside ring...basically the UVs are laid out so it's like you're looking straight down the center of the cone (see UV_layout.jpg).

I used the CC Cylinder effect in AE to render out 1,320 frames in grayscale (see displacement_map_example.jpg intending to use them as an image sequence in Maya for a displacement map. The idea was to "fake" a camera moving through a spiraling tunnel, as the displacement would make the walls seem to move past the viewer.

As you can see from the three different renders, the displacement gets a little crazy nearer the top, and when the tunnel is twisted, it gets even worse.

My guess is that the displacement is being affected by the scale differences in the cone...the wide end is too big, and the tapered end is too little. And when the tunnel is distorted, the polys are of course skewed, and the displacement gets crazy. It makes sense, I just don't know what to do about it.

HELP! user added image

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# 2 16-01-2013 , 02:00 PM

SM Tea Boy
Join Date: Apr 2002

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you could try a mental ray displacement approximation that should help a bit.

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# 3 16-01-2013 , 06:42 PM

The thin red line
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The best way to UV this would be like Pic but I dont think that will help you as there would be a large seam and if you are animating the displacement I dont think there would be a way not to see it, have you delete history and freeze transformation before you animate...............dave

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# 4 16-01-2013 , 07:47 PM

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you could try a mental ray displacement approximation that should help a bit.

Originally Posted by David

Thanks for the reply, David. I'm already using an approximation node on this, which helps with render times, but not with the problem I am having...unless I'm not using it to it's fullest potential. I'll look into it.

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# 5 16-01-2013 , 07:55 PM

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The best way to UV this would be like Pic but I dont think that will help you as there would be a large seam and if you are animating the displacement I dont think there would be a way not to see it, have you delete history and freeze transformation before you animate...............dave

Originally Posted by daverave

Thank you for the response, daverave. You have been helpful to me on other occasions user added image

Regarding your suggestion, I don't see how that would help my problem. I'm not struggling with the best UV layout, or seams....I've already found a solution to both of those issues. My concern is the imbalance of the displacement at its extremes, near the top and bottom of the cone. In the middle, the displacement is very nice, but it's too little at the tip and too much at the top.

Actually I think that David has a good point...maybe I can fix this with other settings in the approximation node, like Min/Max or something...

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# 6 16-01-2013 , 10:33 PM

Lead Modeler - Framestore
Join Date: Feb 2003

Location: UK

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Its worth noting here that for starters I wouldnt use a cone just use a long cylinder with a focal length on the camera of say 22 to start with and go lower if you need to. Sometimes a forced perspective with objects can counter act the illusion so just go with a proper tunnel, the low Focal setting will help put more perspective on it.

Displacement maps are not great for distorting generally, you are essentially putting a 2d image and bending/twisting so its going to have an adverse effect on its the objects uv and final look. Also the jagged edges on the render will look like this the closer you go especially with that low amount of polys on the mesh, Increasing the amount of polys will help smooth it out.

There are ways to set up animated displacements but they are hard to control because you will get a swim effect because of the afore mentioned distorting of the mesh. Its not uncommon to 'drive' dis maps on character facial expressions but its still hard to do, again it all swims. This is the reason Dis maps were not used on the Characters in Avatar. Facial stuff was all 'in mesh'

The Approx node will help raise the displacement or lower it, and you can also make the distortion finer by using the spatial setting. with say 3 min 5 max to begin with, and length on 0.001

cheers
Jay

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