Mumbai university > Comp > SEM 4 > Computer Graphics

Marks: 5M

Year: May 2015

1. The viewing transformation converts objects from their 3-dimensional camera-space coordinates into the appropriate 2-dimensional raster-space coordinates.

2. The camera coordinate system is a coordinate system with the camera at the origin, looking out over the positive z axis.

3. It is, essentially, the scene from the camera's point of view. The raster coordinate system is the space of the pixels on the monitor.

4. Connecting these two coordinate systems there is a special coordinate system known as the screen coordinate system.

5. The screen coordinate system is, conceptually, the same as the film plane of a camera.

6. It is usually best to consider both the screen coordinate system and the raster coordinate system to be two-dimensional, even though we know that RenderMan can output depth information.

7. The RenderMan Interface Specification has a rather complex viewing transformation. The interface has many calls which each set-up a small piece of the transformation.

8. Each of these values has a “reasonable” default, which is to say that if you don't set it, it will default to something which is probably appropriate, given the values that you have already set.

9. The viewing transformation has lots of controls, but typically they are not all used together. Rather, a couple important controls are set and the rest are let to default to their “logical” values.

10. The viewing transformation can be broken down into two pieces, the camera-to-screen projection and the screen-to-raster projection.

    • The camera-to-screen projection flattens the 3-D world onto the 2-D screen.

    • The screen-to-raster projection maps every point on the screen onto some output pixel.