View Full Version : how to composite Interacting objects

05 May 2003, 10:00 PM

A guy flying throught a window(breaking it of course)
Layer2- Background
Layer3- Glass Breaking

How to composite this?

Example 2

A manīs head with hair flowing in the wind

Layer1- Head
Layer2-Hair(some in front of the face, interacting with it and the other behind

Iīve found this stuff to be very difficult(impossible for me actually) in compositing.

Any ideas? It might be simple 4 ya, but it would be surely a great step 4 me.

05 May 2003, 11:15 PM
I dont know what software you are using, but you should be able to assign a material to objects that will act as an alpha matte material. So in your first example, when rendering your breaking glass, assign an alpha matte material to your man, any shards of glass that would be obscured by his figure will not render (or will render, but with the alpha channel specifying that area as transparent), so you will end up with a breaking glass with a man shaped hole cut in it. Same goes for your hair, an alpha matte material on the head will effecivley cull any hairs that pass behind the head.

05 May 2003, 10:14 AM
so if i got it, i basicly have to render my man as a "Matte shadow" right? Using 3dsmax to render & AE5.5 & COmbustion2 for compositing

05 May 2003, 11:06 AM
Yup, thats the one 'Matte Shadow'. Seems you've got combustion & Max, have a wee lookie at 'rendering to layers' in the max help, & 'combustion & max integration' in the Max & combustion help. Max can split your scene into layers, automatically creating a combustion workspace that correctly orders & transfer-modes them - really helpful if you are doing some complicated compositing. Also rendering to RPF format, using things like coverage, object ID's, rendering occluded objects, rendering Z Depth, Velocity, Material ID's etc etc can be extremely powerful. For example you could conceivably select & colour correct the man & his reflection in the breaking glass, adjust the transparancy of the glass & replace the background - all while rendering out just 1 RPF sequence... :)

05 May 2003, 06:02 PM
wooo, that would surely rock! I gotta look into it


Are layers related to The object Id ? I was kinda sad since i tought max couldnt support layer rendering like maya does, but seems i was wrong.

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