Answer to Question #269344 in 3D CAD Modeling for King

Question

Write short notes on the following:

a) Projection

b) affine transformations

c) Phong's Shading Model

d) Scan conversion of polygons

e) B-splines

Answer 1

a) Projection- Orthogonal and isometric drawing views generated from an existing drawing view are referred to as projected views. Projected views can be derived from any existing view, as long as the existing view is not out-of-date or unresolved. The projected views maintain a parent-child relationship with the view it was generated from. This is known as projection.Hi

b)Affine transformations - An affine transformation is any transformation that preserves collinearity meaning all points lying on a line initially still lie on a line after transformation and the ratios of distances. In this sense, affine indicates a special class of projective transformations that do not move any objects from the affine space  to the plane at infinity or conversely. An affine transformation is also called an affinity.

c)Phong's Shading model - this is an interpolation technique for surface shading. It is also called Phong interpolation or normal-vector interpolation shading. It interpolates surface normals across rasterized polygons and computes pixel colors based on the interpolated normals and a reflection model.

d)Scan conversion of polygons - this is a method that uses only integer maths, takes up very little memory, and is simple to understand. The algorithm can be adapted to handle flat or gourad shaded, textured and bump mapped polygons.

e)B-splines - this allows the local control over the curve surface because each vertex affects the shape of a curve only over a range of parameter values where its associated basis function is nonzero.