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sandman01
particular shadow
on Jun 27, 2007 at 10:53:33 am

Hey guys, I've been working on a clip..and I have created some light trails in particular, which fly around and I was wondering how to create a realistic shadow effect for the particles to cast on the ground?



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QueJet
Re: particular shadow
on Jun 28, 2007 at 9:16:06 am

i know of a way to do this

but im gonna say it RIGHT NOW and im gonna ask you strait up

do you wanna hear this?
cause its gonna be 4 pages long, have some very tricky 3d work, your gonna have a WHOLE bunch of play in 3d, and your gonna have to do pre composing, and your gonna have multiple cameras and its gonna be all over the place. Plus it will take me some time to right up o.x'

If you really need this for an effect It can be done, but it won't be easy! Might not be worth it. Oh also this will only work on flat surfaces and it wont work for moving light sources, and distant light sources wont look as good.... annnd shadow blur based on distance from the particle will have to be done manually.
You need this?

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sandman01
Re: particular shadow
on Jun 28, 2007 at 12:52:12 pm

so , here's the thing i've done: I have filmed a live footage of a room, and I have played in particular to get some light trails fly around , rising from the floor and up to the ceilling (srry for my english..not my native language) , simillar like in the ipod video, just a little different. Now, to make it more realistic I need the "streaks" to cast a shadow on the floor and on the walls. I've been trying to do it with corner pin (blend mode set to multiply) and animate the corner pin points but it doesnt get the results i'm looking for..especially because it's not a flat surface..there are also objects in the room. I am very confortable with AFX but not too advanced so if u think I can work that out, I would apreciate you sharing the tehnique. So the video i am playing on is a live footage, not a 3d layers enviroment.



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QueJet
Re: particular shadow
on Jun 29, 2007 at 2:20:30 am

unfortuetly its inevetable that if you want your shadows to be realistic your going to have to translate that live video footage into a psudo 3d room inorder for you to create the shadows.

Ill start work on an example now. maybe make a video tutorial out of it. err ive got no hosting solutions for such things though... meh we will cross that bridge when we get to it.

Expect another reply soon

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QueJet
Re: particular shadow
on Jul 1, 2007 at 3:47:30 am

DARN IT

I was operating on a theory, by using a second identical particular effect, that is the exact same as the one you want a shadow of, changing the camera angle to be that of where the light sources is, then putting that on top of a 3d plane, i would be able to simulate shadows very similarly to how shadows actually work. The trouble is that it requires some seriously complicated corner pinning, furthermore i have to find out how to project a ray from the position of the camera and determine and intersection point between that and the plane im projecting the shadow onto.

Ive had SOME success but its such a tricky setup. I must still play with it, sorry for the delay sandman

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sandman01
Re: particular shadow
on Jul 1, 2007 at 12:02:03 pm

there's no delay QueJet, I thank you for your effort. I'm stil struggling with it. I'll post if I cant get it right..



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QueJet
Re: particular shadow
on Jul 2, 2007 at 9:10:48 am

well the bad news is that ive upgraded to vista, and ive got some serious phone calls and shuffling to do till i get back in order, after effects is one of my first priority's ill have it running soon.

The GOOD news is andrew kramer that clever SOB came up with a projection technique that fits right into my shadow idea. Needs tweaking, but its powerful and will work on multiple 3d surfaces dynamically. like shadows should!
check this out!
Personally i think andrews a bit of a moron with his mindless prattle between very clever after effects techniques.

check it out anyway.

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sandman01
Re: particular shadow
on Jul 2, 2007 at 1:13:20 pm

well, i've seen andrew's tutorial (i am a big fan o videocopilot.net site and andrew of course). I tried the tehnique, and it kinna works, but when I have a lot of detalis and objects in the room I loose the 3d feeling.'I think I am gonna try it with more solids, see if I can get it done..
Btw..do you know some tutorials or tehniques on 3d traking..I think I can do it with 3d tracking but I dont know how to ...I've never done it before:(



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QueJet
Re: particular shadow
on Jul 2, 2007 at 10:42:24 pm

im not a 100% sure how to do 3d tracking myself

to be honest i think its better you work with a reference image

if you have the essential dimensions of the room then you can can create a duplicate version of that room in after effects using 3d layers

then you simply match the camera position and depth of field to that of the room in your reference. Keyframe through the animation re aligning as you go.
Motion tracking would be very difficult. Though i hear that they're plugins out there. so... you know, if you really hate keyframing .)


do you have any project files or anything? Might help me get a better grasp of whats going on and what your trying to accomplish.

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sandman01
Re: particular shadow
on Jul 3, 2007 at 11:16:17 am

I think I am gonna start learning some 3d Tracking. I find it very usefull and unfortunatelly I've been avoiding it because I don't know how to do it, but since I'm kinna stuck right now, I think this is the time to start learning it.
Yes, I can , and I've been thinking about, to recreate the room in AE with 3d layers and keyframe the camera according to the reference, but I think first of all I'll give it a shot with 3d tracking.
The shadows are not that much trouble, just some tweeking and rotoscoping, but I can manage that further..it's the camera position that it's hard to achieve.
I digg a little in tracking, see what I can come up with. I'll post an aep when I get home,right now I'm not on my computer.



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QueJet
Re: particular shadow
on Jul 4, 2007 at 10:57:26 pm

well what on earth can you expect 3d tracking to accomplish?

3d tracking will only give you one piece of data: change.

if you dont have a starting point, what good is that data?

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sandman01
Re: particular shadow
on Jul 7, 2007 at 7:52:53 am

I dont understand what do you mean?



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