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3D Light Rays

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Jeremy Mink3D Light Rays
by on Jul 6, 2016 at 7:37:21 pm

I've set up a multiplane scene using 4 layers I created in photoshop. I'm now trying to give the scene a little more depth with some backlighting.

I'm looking to create some rays of light that originate behind all the layers and will react to the 4 layers I've created (ex. rays will break around a tree). I've tried following a tutorial I found for 3D rays on Video Copilot but I can't seem to get the rays to work in the way I've described. Any tips? Thanks!

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Spencer TweedRe: 3D Light Rays
by on Jul 6, 2016 at 9:43:46 pm

A screenshot would be nice but I think I get the idea of what you're trying to do. I'd duplicate your layers and make them all black, then add a 3D light source behind everything (such as a white layer with a feathered circular mask and some fractal noise). Precomp all of that and then add either trapcode shine or cc radial fast blur to the precomp. If you're using shine you can just use the built-in 3D capabilities to put your lightsource in the right 3D spot. If you're going the cc radial fast blur route then you need this expression in the "center" parameter and a 3D null layer where your light should come from:


You can check "collapse transformations" on your precomp so that it is aware of your camera and you don't have to duplicate it all over the place.

Hope that's clear!

- Spencer

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Soham JaniRe: 3D Light Rays
by on Jul 6, 2016 at 10:01:05 pm

Look up Volumetric lughting by Andrew Kramer on youtube or videocopilot

"It's all around us Neo, temporary constructs of time....."

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Spencer TweedRe: 3D Light Rays
by on Jul 6, 2016 at 10:46:33 pm

Dude, he said he already looked at Andrew's tutorial and is still having trouble...

- Spencer

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Kalle KannistoRe: 3D Light Rays
by on Jul 7, 2016 at 3:10:13 pm
Last Edited By Kalle Kannisto on Jul 7, 2016 at 3:17:36 pm

As I see it, it is going to require multiple passes with track mattes. There is a lessening amount of rays that come through at each layer, so you have to stack them. For the sake of clarity, lets say all four layers are trees.

Moving from back to front, the first layer uses just the first layer for the light rays mask. Simple enough. Just have the first trees layer and then a light rays effect on top of that using the first set of trees as mask.

(To distinguish the two, I'm using the word "mask" to refer to the area where the rays are generated and "matte" to refer to a track matte.)

The second layer uses the first layer plus the second layer as a mask for the rays. But you can’t simply stack them on top of each other, otherwise you double the back rays. You have to use a track matte so that the second set of rays appears only where the second set of trees appears. So you stack the second layer of trees, then the second light rays effect using both layers as a mask AND then alpha track matte the effect with a copy of the second trees layer so it appears only on top of the second layer of trees, and not anywhere where there is transparency.

For the third step, you add the third set of trees, then the light rays masked with all three layers and alpha track matted with a copy of layer three of trees.

For the fourth step, you add the fourth set of trees, then the light rays effect with all four layers and alpha track matte this with a copy of trees layer four.

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