Viewing Transformation
In previous section, we have discussed about the geometric transformations as Translation, Shearing, Reflection, Scaling and Rotation. Rotation, Reflection and Translation transformations are utilized to manipulate the specified object, but Scaling and Shearing transformations are utilized to modify the shape of an object, either in 2-Dimensional or in 3-D.
A transformation that maps 3-D objects onto 2-D screen, we are here called it Projections. We have two kinds of Projections that are: Parallel projection and Perspective projection. This categorization is based upon the fact where rays coming from the object converge on the centre of projection or not. This projection is termed as Perspective projection; otherwise it is Parallel projection, if the rays coming from the object converge at the centre of projection. In the condition of parallel projection the rays from an object converge at infinity, as not like perspective projection whether the rays from an object converge at a finite distance that is termed as COP.
Parallel projection is additional categorized into Orthographic and Oblique projection. Parallel projection can be categorized as per to the angle which direction of projection makes along with the projection plane but if the direction of projection of rays is perpendicular to the projection plane so this parallel projection is termed as Orthographic projection and also if the direction of projection of rays is not perpendicular to the projection plane so this parallel projection is termed as Oblique projection. The orthographic or perpendicular projection appears only the front face of the specified object that includes only two dimensions: width and length. The oblique projection, conversely, shows the front surface and the top surface, that includes three dimensions: height, length and width. Consequently, an oblique projection is one way to demonstrate all 3-dimensions of an object in a particular view. Isometric projection is the most frequently utilized type of axonometric projection that is a method utilized to illustrate an object in all three dimensions by length, width as well as height in a single view. Axonometric projection is a type of orthographic projection wherein the projectors are all the time perpendicular to the plane of projection.