3D modelling / texturing query

[WulfstanDesign]

Bit of a long shot I know, but somebody may have encountered this before. I'm wanting to expand on my green screen skills, so alongside using AE I also use 3D Max. One of my many past projects was a  "Mayan" inspired corridor, which I'd like to reevist and use in an AE green screen project.

So my queries are these. When building the scene what scale do I use? I've seen mention of building 1:1 scale, with texture maps to match. The other option I've seen is gaming scale, with textures being 512,1024,2048 in size. Can anybody offer any advice?

[Mylenium]

I'm not clear what you are asking. AE is strictly pixel-based, so actual scale has no meaning at all and if all your assets are custom made with no relation to an existing realworld scene it's just as arbitrary. Your tunnels could be the size of an alien space hangar or as small as a mouse tunnel and nobody would know the difference. As far as textures go, the old 3D design rule applies: Textures should at least have double the resolution of the intended output size if a polygon covers around two thirds of the camera window. So typically, a texture for a full height wall being visible 50% in the scene in an HD shot should ideally be at least 2k on its shortest side if it's not tiled. The rest follows this logic as well, though depending on motion blur , camera DOF, lighting setup and otehr considerations you can get away with lower-res textures many times.

Mylenium

[Rick Gerard]

When I am creating a texture for a 3D model I consider the percentage of the frame that will be filled with the model and the frame size of the video. Let me explain.

The projecet calls for a 3D model of a 1930's bottle of Coca-Cola. The video frame size is 4K, and the story board requires me to start on a closeup of the bottle cap and pull out to reveal theentire bottle. That tells me that the texture map for the bottle cap must be very close to the same frame size as a 4K video. The texture map for the bottle cap that should be about 2160 x 2160. 

The 3D size of the model has nothing to do with the size of the texture map, but the number of pixels in the texture map has everything to do with how much of that texture map will fill the frame.

If there is going to be some motion blur or the shot is moving, or you only see the top of the bottle cap for a few frames then the texture map can be smaller. There is a little wiggle room here, but generally, if you are going to fill the screen with anything other than vectors, you need to match the frame size as close as you can.

As far as the scale for the 3D models, I like to make them big enough that when I add a normal camera in it's default position, they are about the same size that they will be in the hero shot of that model. In this case, I would make the bottle big enough so that I did not have to scale it up in Element 3D, or C4D lite to fill the frame. You can usually get very close to that when building models if you add the equivalent of a camera with a 50mm lens to the comp, Put a text layer or shape layer at comp center, then export a C4D scene from the comp and check the camera coordinates.