Page 125 - DCAP504_Computer Graphics

Computer Graphics

Table 8.3 illustrates the difference between gouraud and phong model.

Table 8.3 : Gouraud vs. Phong

Gouraud Shading Phong Shading
Intensities are interpolated Normal are interpolated
It’s expensive Three times more expensive

Restricted to Diffuse Component Specular Reflection

Source: http://www.vrarchitect.net/anu/cg/Illumination/shadingSummary.en.html

Browse the net and study in detail about the different shading models.

8.2 3-D Transformation
A transformation is the process of mapping points to other positions. The manipulation viewing and
creation of 3-D images require the use of 3-D geometric and coordinate transformations. The 3-D
transformations are implemented from 2-D methods. They are also formed by composing the basic
transformations of translation, scaling and rotation concepts as discussed in the previous section. These
transformations are represented in matrix transformation with homogenous coordinates. They are
formed by combining matrices for individual transformations in sequential order.
Transformations are used in mapping spaces along the graphics pipeline. In the extensions from 2-D to
3-D, the following changes occur:
1. An additional vector is added, totally 2 vectors
2. Extra column and row gets added to the matrices
3. Singular Value Decomposition (SVD) remains working in the same way
Some of the properties of 3-D transformations:

1. Lines are preserved
2. Parallelism is preserved
3. Proportional distances are preserved

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