Page 212 - DCAP504_Computer Graphics

Unit 13: Advanced Computer Graphics

The figure 13.15 depicts the process of morphing a single vertex using two morph targets. This method
uses linear interpolation to calculate the position of the final vertex. The following figure 13.15 depicts
the method involved in vertex morphing.

Figure 13.15 Vertex Morphing

Source: http://www.mdxinfo.com/tutorials/hardwarevertexmorphing.php
Morphing techniques are used in 3-D modeling packages. However, in real time graphics it is used to
interpolate to a specific target and a subset of the vertices is morphed. Although, this technique is not
very popular, it is considered to be an efficient one. This technique is used for animating models with
complex and active morph targets. The following is the example of the Johnny fish character, a 3-D
animation created many years ago. The creation of the character is explained using multiple vertex
streams.

Rendering the Johnny fish character (animation character) with three
morph targets.

The example on multiple vertex streams can be analyzed by the following example. The Johnny base
mesh was loaded to set 4 separate streams where one was a base mesh while the other 3 were targets.
This was done by using the appropriate vertex declaration to interleave the data on the GPU. Thus, it
was possible to access the morph target vertices in the vertex shader and the final vertex positions were
interpolated based on the weights set for each of the targets.

The two methods by which images can be morphed are:
1. Forward Mapping: In the forward mapping method, the pixels from the source images are
mapped onto the destination image at appropriate places. There are possibilities of some pixels
not getting mapped on to the destination image. In this situation, interpolation is used to
determine these pixels. The point morphing algorithm uses this method of morphing.

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