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casting shadow for bluescreen composite with 3D and lights
Hey guys-
This is something that I know I should be able to do, but am having a hard time getting my brain around.
I am making an image of a guy hurling over a landscape. I am compositing keyed out footage of a figure onto a background of a moving landscape shot from a car. I am trying to place a cast shadow from the figure onto the ground for heightened effect. My first clunky attempt was to animate a solid with a mask (an oblong shape loosly modelled after the figure) with the feather and opacity cranked up, along the ground behind the guy. It looked okay but lacked realism cause the shadow movements don’t really correspond to the dude.
Then I thought of 3d layers, lights and shadows. My idea was to set up a light situation in a 3d environment where my keyed out footage is only set to cast shadows onto a white solid which accepts shadows but not lights. This way I can have a spot light and control the shadow diffusion so that there is a cool feather in the shadow. Then I’d just output the shadow movie on a white background and then extract the white, leaving a transparent shadow layer that I could parent to animated position of the composited figure in my final shot.
My difficulty is setting up the model in 3d space. My footage was shot in late afternoon, so I want to match the long shadows on the ground. I’m not sure how to orient the keyed out figure in relation to the white background and where to place the light, in order to cast the proper shadow.
Has anybody done what I’m describing? -
5 Replies
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Well, you could do:
-Precompose your Keyed guy.
-Duplicate him.
-Apply the effect Perspective > Drop Shadow the duplicated layer.
-Make the duplicated layer a 3D Layer.
-In the effects window of the duplicated layer, turn on “Only Shadow”.
– Then, just play with the X and Y axis of, you guessed it, your 3D Layer so it looks like his shadow’s on the ground.
Play with the feather, opacity and distance and the scale of the 3D Layer (shadow) itself.
Hope that helped.
Justin Productions
Tangerin01@hotmail.com
Adobe After Effects 6.0 Professional -
A perfectly flat ground is going to have perspective lines that converge on the horizon, so that’s your starting point.
To figure out the angle your light should be, try to find something in your footage that’s pointing straight up and down, with a visible shadow. Then add your own thing that’s pointing straight up and down, and get the shadows parallel.
Then maybe use the car footage as a distortion map on the shadow so the ground isn’t completely flat.
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Hi Jason,
If you haven’t figured this out yet, a good solution is this: duplicate the keyed layer, add Effect>Render (Generate in 7)>Fill; change default red color to black. Lighten opacity and soften as needed.
Then add effect>Distort>Transform and adjust the transform settings to accomodate the background.
You’ll want to look at the Skew Angle and amount as well as rotation inside of the Transform effect to get a perspective look.This will take the render hit off of using 3d and lights.
Good luck-Don
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Just to chuck something else in. Blur the shadow version of the guy and set the transfer mode to colour burn, you can get a really nice flowing effect as the black colour moves over different parts of the background.
Graham
https://www.qcit.co.uk – web design
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https://www.shiveringcactus.bravehost.com – Free FX for amateur films -
This should be a feature request.
You can have an object Cast Shadows “Only”, but not have an object Accept Shadows “Only”.
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