Hi, I am trying to composite a model of a stone object into a grassy area shot with a moving camera using Element 3D. After tracking the plate and setting up E3D everything looks perfect in RAM preview except the base of the model is perfectly flat against the irregular grass when it needs to have some of the grass sticking up in front of it. I'd like to present my technique and see if anyone has a better way. Midway through the footage I save the frame as a PSD. In Ps, I add a new layer of white, reduce the opacity to see the model, and use an irregular brush to paint black along the model base to approximate where the in-front grass should be seen. I save just this layer as a JPEG and import it to the AE comp. I make this 3D and position it at the model and rotate and scale so the black fully covers the base of the model. Then, I use it as a luma matte which allows tufts of the grass to show through the model where its looks like it is in front of the model. CLEARLY this is all an approximation, an illusion. I'm certain others have had to deal with this problem. Is there a better way? Thanks for your help.
Sounds like a legitimate technique. Personally I would have taken a frame of the grass itself, with the matte already applied, and put that in 3D space, that way the matte is less likely to slip against the original image. But if your way worked, then fair enough.
CLEARLY this is all an approximation, an illusion.
Sounds good, but without seeing the footage and the final comp it's hard to give precise feedback. It may be that you could use several layers of grass in 3d space. A matte with the original grass footage on top may be what you need, but it may be that you could use some animated grass created in Particle Illusion comped on top using a 2d track... hard to say.