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Lion V,
Yes, that's essentially what it is. Here's the process more accurately stated:
A grid mesh (usually non-linear, like bicubic, catmul, etc.) is chosen for each image (source & dest). The mesh for each image is manipulated to hilight the features of each image. Note that both image meshes have the same number of vertices, so they can be easily morphed (interpolated) from source to dest.
When manipulating the meshes for each image, it's important to align key hilights of one image to key hilights of the other image. For example, in the grid mesh, vertex [3,3] might be the center of the left eye of the girl. Properly setting up the meshes means that you would need to place that same vertex (3,3) in the center of the tiger's left eye. Given that concept, let's take it a little further. The vetices mean very little, other than to control the shape of the curved mesh, so importance is really placed on "outlining" key features of each image, rather than placing vertices where they belong. This, combined with a good set of source/dest images (i.e. images with many similarities) are what make for a good morph.
The images are constrained by their mesh, so as the mesh changes shape, so does the image within (via filtering.) Note that not only is the mesh nonlinear, but so is the filtering. It's not bilinear or trilinear, but rather it follows a curve that is interpolated along each scanline of the image.
The actual process is a frame-by-frame morph of the source image's mesh "shape" to the destination mesh's shape. This "tweened" mesh is then used for both images -- they are both warped to fit this single tween mesh. This means that at the start of the morphing animation (closest to the source image's parameters), the destination image is radically warped. As the morph nears the final frame of the animation, the destination image is warped less, but the source image is the image being radically warped.
During this process, a crossfade takes place. This crossfade helps hide the artifacting you get from the "radical warping" near the start and end of the animation, because the image being most radically warped has the least amount of influence on the crossfade.
That might be a bit confusing, but that's the process. ;)
- MidNight
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