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Casting shadows from other compositions?

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Jon Emmerich
Casting shadows from other compositions?
on Sep 9, 2014 at 10:53:49 pm

Sorry if this is a re-post... I've looked around and can't find anything quite like this...

I'm trying to create a map of Florida with several little points that pop up along the way as the camera flies around/over the map. The map itself is somewhat render-heavy (with flow-y water all around, etc.) so I've placed all the other elements in separate layers, each with their own cameras that match a single "master camera". By putting all the layers together in a composition, I have my finished, 3-dimensional project, but it allows me to render each piece individually so it doesn't kill my computer.

Here's my question: Is there a way to have composition with 3d elements correctly cast shadows onto another layer/composition? Or, perhaps more to the point, is there a way to cast shadows on these layers without having to actively render them? Bare in mind that I may want to change my camera settings along the way, so pre-rendering my map isn't really any option.

To give a specific example... As the camera flies over the map, a pushpin drops from the sky and plants itself in the map. I can get the shadow to cast correctly onto a shadow-catching layer within the pushpin's comp, but when I put that comp onto the map comp, the shadow is lost, because those two layers are 2d.

I hope this makes sense. I'm feeling defeated by a lowly shadow.

Thanks in advance,

~Jon Emmerich
Emmerich Video Productions


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Roland R. Kahlenberg
Re: Casting shadows from other compositions?
on Sep 10, 2014 at 3:15:44 am

I'm not sure what you're asking since it seems like you know that 2D layers cannot cast shadows and you do have 2D layers. Perhaps you can try explaining a little clearer?

For 2D shadows that mimic 3D shadows, try Effect>Perspective>Radial Shadow. By keyframing shadow distance, light direction etc, you should be able to get your 2D shadows looking 3D-ish.

HTH
- Roland

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http://www.broadcastgems.com/mographintensity_shapestext/


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Jon Emmerich
Re: Casting shadows from other compositions?
on Sep 10, 2014 at 3:46:43 am

I guess the core of my question is this: can I take the 3d shadow information from a comp and layer it over other comps? Can I get the shadow info alone in its own layer?

Going back to my pushpin example...

I have 3 comps in play (actually MANY more, but for the sake of example)... 1. I have a fancy, pretty, render-heavy map of Florida with a camera flying around, 2. I have a pushpin that comes down and lands on the map (utilizing the same camera information so that its relative position stays in sync with the map), and 3. I have a comp that layers the two together (I'll call it "comp3"). I do this so that I can render each comp separately, and then combine all the rendered pieces into the finished product. I'm not sure if it's the greatest technique, but it doesn't kill my computer and it gives me the ability to easily go in and make changes without spending a day and half to re-render everything after my client says "You know, it's great. But could the pushpin be blue instead?"

In the pushpin comp, I used a single frame of the florida map as a guide layer. The shadow casts just fine there, but when I jump over to comp3, the shadow is gone because the guide layer is the only thing receiving the shadow. I've tried using a white solid "shadow catching" layer and setting it to multiply mode, but that doesn't work because there's nothing underneath it to multiply to... in comp3 you just see the white layer underneath the pushpin.

I guess what I want is another layer with just the pushpin's shadow, so that in comp3 I can sandwich it between the map layer and the pushpin layer, creating the illusion that the pushpin is casting a shadow on the map.

Clear as mud?

Thanks again for your help,

~Jon


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Roland R. Kahlenberg
Re: Casting shadows from other compositions?
on Sep 10, 2014 at 7:43:57 am

Hmmm ... if what you want is a Shadow Catcher layer then do as follows -
1) Set the shadow casting layer's Cast Shadow prop to Only
2) Set the floor/map area's Accept Shadow prop to Only
3) Ensure that your comp's background is set to full-on white

When you comp this Shadow Catcher layer, set its Blending Mode to Multiply - this BM will composite the layer with the white areas removed; leaving on the shadow. Take note that the Shadow Catcher layer is now a 2D layer. As such take note of where it is placed in the Timeline hierarchy if you have 3D interactions between/across other layers in the comp, since 2D layers will get in the way of 3D interactions involving layers below/above it in the Timeline hierarchy.

HTH
- Roland

TypeGEMs - the Definitive Type Gizmo for AE
http://broadcastgems.com/typegems/

Intensive mocha & AE Training in Singapore and Other Dangerous Locations
Adobe After Effects CC ACE/ACI
Imagineer Systems (mocha) Certified Instructor

http://www.broadcastgems.com/mographintensity_shapestext/


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