Actors in 3d world

#1

Hi, I am just trying some stuff for a movie I’m gonna make soon, but I have some questions. I am making a 3d world for the actors to walk around, and I also have a bluescreen studio for the filming. Also, I can put little crosshairs of tape on the bluescreen as reference for matchmoving software. But then? Do I just have to put the chromakeyed video on the 3d scene? Or can I do some more. The idea is this: two actors are virtually standing on a train. The whole lighting stuff is not a problem. But what if I have an overview shot with the actors on the train? I can’t place a camera 100 meters away from the bluescreen studio. Is there some way I could place the chromakeyed actors on a plane without having the whole composition look unrealistic because the plane and the actors in it are flat? Also, what about the shadows the actors should make on the floor?

I’d really appreciate some help on this subject.

#2

It is close to what I am looking at doing, I don’t have the answe yet, BUT I do have some ideas to go at it with.
As you said you can’t make the camera move 100 M from the “Tallent” but I guess distance is a perceptual thing right? Size. So is it not possible to reduce the size of the tallent image in post, scale it down like they do in news with the over the shoulder crap. Without seeing the train or understanding teh shot exactly I will be limited in some ways to answer, and I am sure that many others will be too.
Is it psooable to get a story board shot of the scene as it will be, even a scketch. then I amy think of a work around. That is all it is right working around the problems, lol/ I will be intrested in helping you come to an answer, as I said it helps me too;

#3

Hi, thanks for the reply

I do think the distance matters, because at a further distance from the subject, the subject has less perspectivity. On one actor that won’t be a big difference, but with two actors, their relative position to each other gets wrong if the subject they are standing on gets a different position.

But I don’t think this is a too big difference, I mean, look at the shot in the Lord of the Rings - The Fellowship of the Ring, where you see Gandalf flying towards you on an eagle. At that point it really looks like the actor is just placed on a plane and the plane just placed on the eagle.

#4

that is along my thinking, what you would have to figure out is how to visualize the pair, and think of how it will change from a distance and all. Then jsut think of it in the context of the train, I will be thinking more on how, at the same time I am looking into thei in other forums and with google, and help text from Max and Primere Pro

#5

Well I have been in the process of learning this all myself in the last few years. I haven’t had time to write up any kind of tutorial on the process I use to do this stuff, step by step.

But I will give you some keywords you can search for that will lead you in the right direction.

  1. Filming greenscreen or chroma keying - the process of correctly capturing your greenscreen and tracking markers. (lighting, camera setup and movement)
  2. 3D pixel tracking - the process of tracking 3d trackers or set data to reconstruct a 3d camera movement (this also includes removing lens distortion)
  3. Keying greenscreen or keying chroma - the process of removing the greenscreen and getting a good edge. (this also includes masking out the TRACKING MARKERS)
  4. 3D - this is all about making a 3D scene in whatever program you are using and is to broad to give anything specific (things to watch is light placement, needs to somewhat match your live action footage.)
  5. Creating shadows from greenscreen - the process of recreating shadow elements to tie the flat greenscreen footage into the 3D world (this can be done in the 3d program or in a composisting program)
  6. Compositing - the proces of taking all your layers, slapping them all together, and making it work (this is VERY BROAD depending on the complexity of your shot. it may just be a actor infront of a simple background or complex like a camera movement with 3d moving lights and shadows, to huge camera moves, or interaction between live actors and 3d objects, and so on.)

at least for me, this is what I searched for. not to rain on anyone’s parade, but this stuff, if you want it to look good, by good I mean something that could pass for a TV show, it’s not easy. there is no “one” way to do it, there are tons of variables, it takes time and patiences to pratice.

I suggest starting small and simple. take a big box, break it open, paint it green, light it and put some stuff animals in there and try to pull the key, track it and put in a 3d background.
sure it’s not fancy and cool, but you can work things out really easy on a small scale, then take that, scale it up to full size. all the pros started off small. for Return of the Jedi they took toys and flew them around carboard tubes painted like trees to work out the Speeder Bike scene.

alot of people I know just jump into large projects, never learning the basic, then can’t figure out why things look like crap.

as for the specifc thing about big camera moves, you can do those many different ways. use a digital camera move. by that I mean film your actor FULL FRAME, turn the camear on it’s side, film them to fit the whole frame. this will allow to you zoom slighty into the image and not get pixelated. you can then do a mega zoom up to the point you see pixels. the camera can move a bit, remember your TV is flat to, as long as you don’t go to many degrees off axis you won’t see that the actor is flat. you could even warp the FLAT the actor is on, givening it a little more dimension.

now if you want a complex move, then you need to think of other ways to do it. maybe time the actor to turn to their side slighty and then fake a dolly around them, this would look like the camera turns a big at the end. or do a blend of different camera angles. or replace the actor digitally. this seems to be the norm these days.

I do shadows right in MAX. shadows are flat projections based off the alpha channel you get when you key your footage.

#6

For distance matters consider the use of a mirror in front of the actors and the camera shooting looking at it, You´ll have to take care of the angle used as to not show the camera in shot while at the same time avoiding shearing in objects due to the mirror´s angle. Of course the camera should be close to the bluescreen but out of frame.
This way you can either duplicate the distance from camera to the actors, or move the actors away from the bluescreen.
I learnt this from my filmmaking teacher, who used the trick regularly when shooting in small spaces for several tv series he used to direct. Even DOF works this way.
I remember he using it in a really shallow swimming pool that in the movie looked much deeper because of this.

good luck
JC

#7

Man thanx for the pointers, the work small and scale up approche is a good one, as well that mirror trick that one is going into my personal tool box.

#8

My mentor (teacher-art Director-friend-master-sensei-kind of thing) has mentioned use of mirrors back in the day (when Quantel was cream of…) Ive never seen it done though!

Very interesting… hmmmm (ponders)

#9

WOW, thank you for all your replies!!!

I allready made a tiny bluescreenstudio out of a box (1x1x1 meters) and I put crosses with a darker blue on it for the tracking. Unfortunately the tracking was not very accurate, because the crosses were too big and too far away from each other, but it’s a start. Then I let my rat walk in it, and filmed the whole thing. Then I keyed the movie. I just made a 3d box in 3dmax and rendered with the tracked camera, and then I put the keyed movie on top of the 3d in premiere. But then I don’t have any shadows. In this case, how should I make the shadows. Just using the alpha is not very easy, because the rat moves, also up and down, so I won’t be able to just stretch the shadow to match the lighting.

If I would make the train scene, should I then just film the actors from up close, and put them both on a plane and put those planes on the train, and then put a light on those planes, so that their shadows are projected on the train?

I’m still a little confused, but things are getting brighter allready.

Again, thank you for all your replies!

#10

how are you doing the 3d tracking? you are going to need to use a good 6 to 10 if you are using MEASUREMENT based tracking, or atleast 20 if you are going to use IMAGE based tracking. also the 3d tracker in 3dsMAX is a joke, you would be lucky if you ever got it to ever work on the tutorial. don’t waste your time is my suggestion, just go buy a cheap 100$ pixel tracker, you will save a butt load of time in the end. (and you need to have those MIN about of trackers in the camera view at all times, so if you move your camera one way or around randomly, you may need 2 to 3 times as many markers, to always make sure enough are in the view)

depeneding on the blue you are using, try WHITE or PINK tape. remember that pixel tracking works of CONTRAST so you need to make sure that your markers contrast your screen enough to hold good edges. I use 3inch by 3inch light blue crosses every 2 feet on my green screen and my camera is about 20 feet away from it. by the time I get the video into my computer, the crosses are JUST big enough to track.

since you have have to light your 3d scene, just use those lights in MAX to cast your shadows. key out the real shadow and then map your rat footage onto a plane with an alpha, posistion that plane in the 3d space where it is in the real space corisponding to your camera placement. then render out a sperate shadow layer only, this will allow you to control the shadow in your composiste better.

#11

Douglas Trumbal used the “mirror trick” for the final mothership shot in Close Encounters. The stage area wasn’t large enough to get far enough away from the model as it flys away to make it look small, so he shot it in a mirror. Looked great to me…
E.

#12

I find really amusing that still today, the easy way of doing some type of effects is the old way. We are way too confident with digital technologies and sometimes don´t realize that everything has already been invented.

As an example: Introducing DOF in a take shot in a small studio (will forget the bluescreen)

[ul]
[li]Digital approach: Shoot time, time taken to rotoscope the actors in the whole sequence, clean up the mattes, add the DOF filters, color correct and create final shot: anything from 1 day and up (will depend in the number of frames to process) [/li][li]Old approach: Time taken to place the mirror, the talent and the camera (with proper lens set up) and shoot the take: from 1 minute to 5 minutes, and it will be the real thing. [/li][/ul] In-Camera effects should always be considered as the first option, as they tend to be much faster to set up. The problem is that a solid lens geometry and lighting conditions knowledge are needed.

Trumbull, Harryhausen, George Pal, early ILM years, … good experiences to learn from them.

JC

#13

I’m not sure how well the Mirror trick will work with a DV camera. remember there is a big difference between a typical DV camera and a high end DV cam or film camera. namely a prime lens. but there are a lot of people building there own prime lens adapters for DV cameras so you could have true DOF, focus shifting, etc.

take a peek here

http://www.dvinfo.net/conf/forumdisplay.php?s=&forumid=70

some of these are made out of hand ground glass and PVC tubing! because a pro lens adapater cost up to 1500$

I have tried to do DOF with my Sony PDx10 but I have to be extremely far away then zoomed all the way in before I can cause the background to go out of focus.

#14

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