Page 211 - DCAP504_Computer Graphics

Computer Graphics

Image morphing is a technique used to bring about 2-D transitions between images. It is difficult to
correct image morphing manually due to its unnatural distortions.
The technique of morphing involves changing the shape of image over and over again into another
image. Morphing is generally used for visual effect purposes where a normal looking person can be
morphed into a cartoon character. Using simple morphing with 2-D images and with a basic knowledge
of after effects, it is possible to complete the task of morphing at a very fast pace.
Simple morphing happens due to the concurrent happening of three events such as:
1. Morphing the shape of the source image to the same shape to that of the final or destination
image.
2. Warping the final or destination image to the source image without distortion to retain the normal
shape.
3. Changing due to distortion causes the destination image to become visible over the source images.
The following figure 13.14 depicts the various transformations that can be made on an image. The first
row of images show the morphs made between two views of the same person. The second rows of
images show the morphs between views of two different people. In both the rows, morphing captures
the change in facial pose between images I 0 and I 1. This image conveys a natural 3-D rotation.

Figure 13.14: Image Morphing

Vertex Morphing
Vertex morphing is a process which allows deformation of a base mesh by using morph targets and
meshes, with identical vertices but having altered vertex positions to the base mesh. The vertex
morphing technique is used for bringing out facial expressions on 3-D characters. As, the
transformation of the image cannot be described due to the presence of bones on the face, vertex
morphing method is used.
Let us now analyze the working of vertex morphing as shown in figure 13.15. Vertex morphing works
on the principle of interpolation where the final vertex position between a base position and a target
position is defined in separate meshes known as morph targets.

204 LOVELY PROFESSIONAL UNIVERSITY