Creating a CG movie background


(thelonesoldier) #1

I’m looking for a way to create a CG background for a short film. The actors will be placed into the environment via green-screen. I need to be able to produce simple camera movements (probably just pans and basic linear movement) so that the actors can move through the environment a bit and the shots aren’t all completely stationary.

Someone suggested Blender to me, but he’s only passingly familiar with it and doesn’t know all of its capabilities. I’ve been learning the basics but I haven’t found a tutorial that covers what I’m trying to do. I guess basically what I need to do is create environments (probably small and medium sized rooms, maybe an outdoor environment) and be able to move the camera and export the result to a movie.

Is this feasible in Blender? If so, how would I go about doing it? Are there any tutorials that would help me out?

Thanks for any assistance!


(Spin) #2

Are these actors real people?

If so then…

You can actually do this, but it will be tricky.

Video tape the real green screen scene with actors.

Put that video clip onto a plane in blender.

Adjust the camera and plane. Parent them.

Create the Blender scene.

Do the animation of the camera by hand to synchronize the video.

this is hard to explain

Then remove the plane and create the Blender video.

Finally, use your editor to chromaKey the actors into it.

-Also, try ICARUS camera tracker. That may be a possibility
Here’s an ICARUS demo kind of reverse of what you want.


(thelonesoldier) #3

Yeah, real people. That’s why I’d have to green screen them :stuck_out_tongue: .

Man, that’s confusing. I’d definitely need to get help with that. But it is possible?

If someone can explain it better, or point me to a tutorial (if there even is one), maybe I can do a test to see how well it would work.


(miffwhite) #4

Yes that is definately possible-- I’ve done it before and I don’t mind helping out – or giving you ‘tech support’- If you want that is. I’ll be busy for the next two weeks but after that I’m keen to help out. There are generally a few different ways of doing what you want- depends on the shot–

You most likely would just use blender to create the 3d backgrounds. You could also make backrounds from photos etc and modify them in PS or gimp.

I’m not sure how knowledgable you are in this field- but you’d need a compositing program like After Effects to put your characters in the background – There are cheaper options that After Effects. In a few more releases Blender will have it’s own built in node based compositor. Which is going to put a smile on my face.

Also in Blender there is a video sequence editor which can do green screen, although I have never used it. You will have to search the forums to find out about that.

3D modelling ain’t the easiest thing to just learn on the fly- if your work looks promising you might be able to get people to help out on this forum- to do some of the work for you. Sky Captain and Sin City (I Believe) used a combination of 3d and photo manipulation. Sorting everything out from the start is going to make everything easier when you are doing post effects etc-

if you need any help-- feel free to email me at
[email protected]


(Spin) #5

Is this video going to have the same Special FX as in the 70’s TV series “Land of the Lost”?

Wow, you can create some awsome sets with Blender. Do a test-run and post it here.

Here’s what I would do, for testing purposes. A still Tripod and no camera movements.

Get the green screen room ready. I assume you may have a green box or green shelf or some sort of green prop.

Match that up with Blender and see how it looks.


(miffwhite) #6

is this video going to have the same Special FX as in the 70’s TV series “Land of the Lost”?

Did I just miss something – or was that one of the biggest assumptions ever-- Spin are you going a Land of the Lost phase or did that just come to your head? :slight_smile:


(Spin) #7

That just came to my head. I didn’t want to insult his projoect and say “Are you creating a cheesey video like Land of the lost…?”.


(thelonesoldier) #8

Hmm, I should probably explain our project, just to give you a better idea of what we need. I’m in the film class at my high school, which is in charge of making the DVD yearbook over the course of the year. We shoot sports and school events and edit them into short (3-4 minute) features with music. However, rather than just being a collection of features, the DVD is supposed to have a theme and story which connects the features with short (1-3 minute) segments. We decided to go with a Sin City-esque theme with the green screening and everything, but after a lot of brainstorming many of the others have decided that it would be too difficult to pull off technically, because we’d either have to use static shots with photo backgrounds, or if we filmed the background we’d have to match the camera movement perfectly. I still really want to do the theme we came up with, and so I decided to start working on a way to do a 3D background. I was talking about it with one of the other guys and he told me he’d heard of Blender and to take a look at it. So my goal is to create a basic tech demo to prove it can be done, show the demo to the others, and then if they agree it works, do all the 3D work myself (I have incredible amounts of free time, and when I’m interested in something I can work tirelessly at it. And they’ll have far less objections if I’m doing all the work. Plus, if I do the backgrounds, that would probably be my major role in the class and I wouldn’t have to work on video announcements [shudder])…

I’m not sure how knowledgable you are in this field- but you’d need a compositing program like After Effects to put your characters in the background – There are cheaper options that After Effects. In a few more releases Blender will have it’s own built in node based compositor. Which is going to put a smile on my face.

We have Final Cut Pro, which I am familiar with and allows for keying and such, and Premiere 7.0, which I am not familiar with, Motion, which I don’t think any of us is familiar with, and After Affects, which I am not familiar with, but some of the others are.

Also in Blender there is a video sequence editor which can do green screen, although I have never used it. You will have to search the forums to find out about that.

Interesting. I’ll search, but if somebody else happens to know a link already that would be helpful.

3D modelling ain’t the easiest thing to just learn on the fly- if your work looks promising you might be able to get people to help out on this forum- to do some of the work for you. Sky Captain and Sin City (I Believe) used a combination of 3d and photo manipulation. Sorting everything out from the start is going to make everything easier when you are doing post effects etc

As for experience, I have a lot of experience building Half-Life levels in Worldcraft/Valve Hammer Editor. It functions a lot different than a 3D modeler, but that’s still what you’re doing, and I think (or at least hope) a lot of the basics still apply to other programs. Also, making a room is less complicated than a face or body or animal or whatever (at least, in my experience and opinion). With that said, I’m still definitely a newbie with Blender and 3D modeling. Also, I’m not sure what would be the best way to go about making a room in Blender. Would I just make a bunch of different objects and put them together?

Anyway, we have a very large time frame (probably six to seven months), so I’m not terribly concerned about time at the moment. If I can figure out the basics and pull off a successful test than I can spend a long time working on my technique and learning new things.

As for using photos as backgrounds, we already know how to do that, but it really limits camera movement because the background is flat. In the final product we would probably use both photo and CG backgrounds, but I’m not sure… it would depend on how consistent we could get the look.

Here’s what I would do, for testing purposes. A still Tripod and no camera movements.

I’m afraid that would be largely pointless, as we could just use a photograph for that, and my goal is to prove we could have camera movements.

Is this video going to have the same Special FX as in the 70’s TV series “Land of the Lost”?

I wouldn’t know. I’ve never heard of that series. However, as I said, we’re going for a Sin City-esque look.

Get the green screen room ready. I assume you may have a green box or green shelf or some sort of green prop.

We have access to several green screens which hang from stands, one of which is extremely large (I forget the dimensions, but large enough to follow an actor as they walk and use that for walking through a good portion of a room).

Anyway, my goal for the first demo is to build a simple room, maybe with a table or some other small detail so it’s more than just the inside of a cube, and have an actor move through the room. I’d like to do at least one pan, at least one shot where the camera moves alongside the actor while he or she is walking, and maybe a simple rotation.

Actually, if anyone knows where I could get a file of a simple room, I could use that to test it out while I’m still working on my own modeling ability.


(Spin) #9

Here’s what I would do, for testing purposes. A still Tripod and no camera movements.

I’m afraid that would be largely pointless, as we could just use a photograph for that, and my goal is to prove we could have camera movements.

In that case, the answer is YES, you can do what you want to do in Blender.

OK, in order to see if you can do camera movements with Blender, You need to see that you cane do a still in Blender. Once that is proven, you can go on the next step and do it with camera movement.


(miffwhite) #10

I’ll try and upload a video later today - when I shot characters against a green screen and panned the camera. It came off ok for an amature. Also, just because you use photos as backrounds doesn’r mean they have to be static. You could easily animate alpha channel tgas on different layers to add depth. Even if you can’t do it for school – you could just do it yourself with some mates, you said you have plenty of spare time.

You can get blender models here http://www.elysiun.com/forum/viewtopic.php?t=27311 – there is a room some where in there.


(miffwhite) #11

This is what I did with cg backgrounds- start off with 3d-- and spruce up a little in photoshop-- actually a lot. I tried load up the video but could quite manage it. I’ll see if I can get it later. Work based on a comic by Tim Molloy.

http://www.dangersquare.com/fly.jpg


(thelonesoldier) #12

You need to see that you cane do a still in Blender

You mean, that I can create a still, or that Blender is capable of doing a still? All I’d have to do is make something, render it, save the image, and green-screen the actors on top of it. But if you mean for me to model out a scene to make a still out of, I’m not that far yet.

You could easily animate alpha channel tgas on different layers to add depth.

I’d thought about it, but you can’t move through the scene very well. It’s still another possibility, but it would be more limiting. I will consider it however, especially if Blender doesn’t work out. I might even do a test of that soon, it would be easy.

You can get blender models here http://www.elysiun.com/forum/viewtopic.php?t=27311 – there is a room some where in there.

From that thread, I found this site, which has a file called “room” that is perfect for a test. Thanks.

I still don’t have any idea how to go about doing this, so again any help or links to helpful places is welcome.

edit: That looks very good, Miff. I’d love to see it playing in realtime. If nothing else works, you can try a crappy but free no registration filehost like www.megaupload.com.


(Fligh) #13

http://www.weirdhat.com/blender/compositing2/

%<


(thelonesoldier) #14

That doesn’t seem to be very related to what I’m doing after skimming it, but I’ll read it more later. That’s a static shot with CG composited into video, while what I want to do is composite video into CG, and have the camera move.

Incidentally, the author of that tutorial picked a really ineffecient way to do the arm, but if all you have is Blender I guess that might be necessary.


(Ammusionist) #15

Just to clarify - You have (or will have!) some live footage of real actors shot entirely on green screen and you want to replace the green with CGI footage create in Blender. Correct?

I guess a good question to ask first (As all the previous posts seem to vary and I just want to lock this down first): Is the “Live Action” footage from a locked off camera or does it move?

If it moves, is there anything in the green screen footage that can be used to reference the movement (ie: row of dots or seams in the set that show the movement of the cmaera)?


(thelonesoldier) #16

Just to clarify - You have (or will have!) some live footage of real actors shot entirely on green screen and you want to replace the green with CGI footage create in Blender. Correct?

Yes.

Is the “Live Action” footage from a locked off camera or does it move?

As I’ve been saying, the whole purpose of the CG background is to allow the camera to move.

If it moves, is there anything in the green screen footage that can be used to reference the movement (ie: row of dots or seams in the set that show the movement of the cmaera)?

Haven’t gotten that far yet, but that’s a good idea. I’ve noticed when watching special features on big films, they have crosses marked onto the green screen (presumably) for this purpose.


(Ammusionist) #17

Cool - and thanks for clarifying those points.

The main trick to cgi compositing in a situation like this is to make the movements of the camera in the 3D environment match those in the real footage.

This is why you see crosses or dots on the walls in the “Making of…” specials. These provide a reference to the motion of the camera.

There are some tools around that can allow you to convert footage into 3D movement data that can then be imported into Blender for post processing…

You might want to check HERE for a tutorial on how this can be accomplished and HERE for information on one of the tools that can do this.

[edit]Just a footnote to this: you can also achieve some cool sureal effects by NOT matching real and CG movement. Good for nightmare sequences where the background rocks around a person!


(thelonesoldier) #18

Thanks and you’re welcome. I took a look at them, but I’ve already got a splitting headache from trying to model something way beyond my level of skill, so I’ll have to wait until tomorrow to make any sense of it.


(Ammusionist) #19

Old friend of mine once said to me

“Bite off more than you can chew and then chew like hell!”

Good luck on the headache!