Hidden Surface Removal n Purpose n n Identify

Hidden Surface Removal n Purpose n n Identify the parts of scene that are visible from a chosen viewing position Classification n n Object-Space-Methods n Compare objects and parts of objects to each other with scene definition Image-Space-Methods n Visibility is decided point by point at each pixel position on the projection plane

HSR – Depth Buffer n Depth Buffer Method n n n Object Depth : Measured from the view plane along the z axis of a viewing systems. Can be applied to planar an no-planar surface. Require two buffer : depth and pixel (frame) buffer Require large Memory Point by Point test

Projection Normalization n Define n n Convert all projection into orthogonal projections Process

Normalized View Volume n Canonical View Volume n X : -1 ~ 1, Y : -1 ~ 1, Z : -1 ~ 1 n provides a standard shape for representing any sized view volume n clipping procedures are simplified and standardized with unit cube Translation factors Ratios of the dimensions of the viewport and view volume

Normalization –Oblique Projection n n n Tan a = z / (x – x’) => x’ = x – z cot a, y’ = y – z cot b z’ = 0 P = Mortho. H(a, b) => P = Mortho. STH

Normalization – Perspective View n Perspective Projection n Perspective transformation + Orthographic projection

Normalization – Perspective View n Cosider Z n Applied CCV n n Each range : -1 ~ 1 Z = -1