create envelope pieces as separate layers in photoshop > load PS file into Ae as "composition-cropped layers" or just as "composition" > make the layers 3D layers in the layer switch panel > start animating.
Note: if you work with 3D layers as precomposition you'll have to tick the switch for "collapse transformation" also to be found in the layer switch panel (w. little star or sun icon above there)
If you can do it in a 3D modeler, you can do it in AE. But your entire concept of 3D must change. Start with the basic tutorials for 3D scene construction and then learn how to precompose 3D scenes into a master world scene. That is, in your modeler, you easily build a box (a primitive cube) with a hinged flap. In AE you cannot build primitives. Your only building elements are planes that have no depth. So you must think of how you will build and envelope out of objects that are 1-pixel thick, position them in z-space, create a triangle with a hinge, and be able to place your letter inside the envelope. Do you need edges? How will you lock all of the pieces together so you can either move your camera around the envelope or rotate the envelope? Lighting your scene?
It's not very difficult but you canot apply much of what you know from your modeler except the fundamental workflow.
Keep watching the forum and start searching for AE 3D tutorials on the Net, there are hundreds. Lower your expectations for the first several experiments
Simple, but it requires precision and careful planning.
- Create the front and back of your envelope with 3D solids that are 2 pixels apart in Z space
- Make sides if you plan to show the envelope from the side
- Create the V cut in the back with a mask
- Make the top flap with another solid and a mask
- Reposition the anchor point's y value to 0 so that it is exactly at the top edge of the flap when it is down
- Set the position of the flap layer to the same X and Z value as the back and a y value equal to the position of the back layer minus half the height of the back layer to put the edge of the flap exactly at the same place as the back layer.
- Animate the y rotation of the flap layer
- Create an oversized copy of the back layer to use as a track matte for the inside piece matching the v cut on the top
- Position your inside piece between the front and back layers
- Position the oversized back layer just above the inside piece and set it as an Alpha Matte for the inside layer.
You're ready to animate.
If you need a folded piece inside like a letter you can use the same offset trick for the anchor point to precisely line up the edges.
Hope this helps.
Thank you all for your input! I will try some different techniques out as soon as possible. I really appreciate the assistance of professionals in areas that I am no good at!!
Happy Vanentines Day to all.