Rasterisation 2

Learn about rasterisation!

4 cases from the object centered perspective

A partially obscures B, B partially obscures A, both A and B are visible, B totally obscures A

how does object centered calculation scale?

with number of shapes, only works when the number of geometric primitives is small

how does image centered approach scale?

with image resolution, dominant approach

painter’s algorithm

depth sort polygons and paint back to front

what if there is overlap in z direction?

determine if the x and y extents overlap. if they do, clipping will be required

failure case of painter’s algorithm 1

cyclic overlap means no sorting is correct and we have to break polygons

failure case of painter’s algorithm 2

piercing polygons, need to clip polygons against each other by calculating intersections

what is aliasing caused by

insufficient sampling resolution either spatially (number of pixels), in depth (resolution of depth buffer) or in time (number of discrete frames)

sampling approaches to anti-aliasing 1

multisampling creates multiple values per pixel and averages them out when creating the final image

sampling approaches to anti-aliasing 2

supersampling consists of rendering a higher resolution and then subsampling the image to reduce resolution