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GL PROJECTION

lastmod 2024-11-17created 2024-11-172 edits

Among the transformations that take place in the OpenGL rendering pipe,

  • "affine transformation" and
  • "projection transformation"

are included.

  • An affine transformation refers to transformations such as translation, rotation, and scaling of vertices; its characteristic is that it preserves the parallelism and ratios from before the transformation.
  • A projection transformation, given n > m, is a transformation that maps a point in n-dimensional space to a point in m-dimensional space. An example is transforming a 3D point p(x, y, z) into a 2D point p'(x, y).

In the OpenGL rendering pipeline, the "projection transformation" happens after the "affine transformation".

Functions used for affine transformations include

  • glTranslatef()
  • glRotatef()
  • glScalef()
  • and so on, and

functions used for projection transformations are

  • glOrtho()
  • glFrustum(), and
  • gluPerspective() is a function that makes glFrustum() easier to use.

Projection transformation in OpenGL comes in 2 kinds: one is "orthographic projection" and the other is "perspective projection".

To do any other kind of projection, create a custom projection matrix and put it on top of the current projection matrix stack using the glMultMatrix() function.

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