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Align physical model with C4D model
Hi,
I have been browsing through google for weeks now regarding this issue and have not found a solution.
Im working on a film entirely shot in models (scale 1:12 – static shots). My intention is to get alot of different shadows playing around in the rooms, shadows not possible to achieve with real light. So, my hope was to be able to create this in C4d. I’ve done some basic tests in After effects but since i want a higher detail level (lists, doorhandles etc) 3D seems like the only option.
Is there a smart working method to do this. To align the shots with a 3D version in C4d? This would be great since i then can do the light setup/animations/projections here and multipass render the shadows and put them together with the physical model in after effects for some post.
I hope you understand me.
Kindly
Fredrik -
6 Replies
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I’m new to C4D and I’m betting that someone else has a better method than this but this is what I would do.
- Recreate your set in 3D with the exact same measurements or a scale multiplier (e.g. 10x) of those measurements. Texture all the objects with a checkerboard pattern. (Available as a procedural texture within C4D). You might want to set the transparency to 70% or so so you can see through the objects somewhat.
- Create a background object in C4D and texture the color channel (disable Specular) with one of your images.
- Create a camera and move it so that the the 3D model aligns with the background object image. Focal length and such should match as close as possible.
- Now create a white texture and apply that to all surfaces. (Replace the checkerboard).
- Light as normal with shadows turned on. This will allow you to create whatever shadow effects you desire.
- Add Compositing and External Compositing tags to each object in the scene. Create object buffers for each one.
- Render out a shadow pass.
- Render out alpha hold out mattes (or just one combined one) using the object buffers.
- Import into your favorite compositng program and composite over your image.
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I think it would be a challenge to get an exact camera match, but your best shot would probably be to place a bunch of trackers on your physical model — especially at key areas like corners and wall/wall, wall/floor, wall/ceiling junctions, and track the footage in Syntheyes or another 3D tracking program. Then use the tracked nulls as reference to build a 3D scene. Then render from the tracked camera and comp in the shadows.
But if you’re going to do all that you’d might as well just do the whole shot in 3D, eh?
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Adam, can Syntheyes do a 3D solve for static shots? I suppose you could manually place trackers and set up a coordinate system with known X,Y,Z values but I don’t see how that would be an advantage over just building it in 3D.
Can you explain further?
– JC
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Mmm, no, I don’t think any tracker can solve a static shot. Sorry if I missed that.
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Hi Jack,
Thank you for your answer! This technique is somewhat close o what im doing right now but the checkerboard pattern thing sounds really useful. I have just rendered out a shadow pass in my tests. What will the alpha hold out mattes with the object buffers do?
Also, the focal length etc. Im using a 5d mkII and if i understand this right there wont be any calculating since the cropfactor is one (as in C4D). So focal length 50 in my 5d will correspond with focal length 50 in C4D. Am i right_
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What will the alpha hold out mattes with the object buffers do?
I don’t have C4D with me right now to test this but if C4D renders out a shadow pass complete – that is without automatically generating a holdout matte for objects in the foreground then when you layer it in your compositing program the shadows that are supposed to be behind something will be on top of it. Separate object buffer passes would allow you to easily mask out things in the foreground to provide exact control of your shadows.
So focal length 50 in my 5d will correspond with focal length 50 in C4D. Am i right_
In this case that appears to be true because the width of the sensor on that camera is 36mm. The perspective is dependent on the FOCAL LENGTH and the APERTURE WIDTH as well as subject to focal plane distance. The wider your focal length the more critical these parameters are. In this case you just happen to be using a camera with the default APERTURE WIDTH. You may still have issues with optical distortion though (especially with wide angle lenses) and may want to un-distort your image before bringing it in and attaching it to the background object as a reference and then apply that distortion in reverse to your 3D render in your compositing program over the original image so that all convergence lines match up.
Keep in mind that I’m new to the program and all is this is from my perspective as to how it should work and not any significant amount of practical experience (yet).
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