How does zooming, panning and rotating work?

Question

Using OpenGL I\'m attempting to draw a primitive map of my campus.

Can anyone explain to me how panning, zooming and rotating is usually implemented?

For exa

Answer 1

Generally there are three steps that are applied whenever you reference any point in 3d space within opengl.

Given a Local point

• Local -> World Transform
• World -> Camera Transform
• Camera -> Screen Transform (usually a projection. depends on if you're using perspective or orthogonal)

Each of these transforms is taking your 3d point, and multiplying by a matrix.

When you are rotating the camera, it is generally changing the world -> camera transform by multiplying the transform matrix by your rotation/pan/zoom affine transformation. Since all of your points are re-rendered each frame, the new matrix gets applied to your points, and it gives the appearance of a rotation.