Hidden Surface Removal

1
Hidden Surface Removal

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

2
HSR Depth Buffer

• Depth Buffer Method
• 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

3
Projection Normalization

• Define
• Convert all projection into orthogonal
  projections
• Process

4
Normalized View Volume

• Canonical View Volume
• X -1 1, Y -1 1, Z -1 1
• provides a standard shape for representing any
  sized view volume
• clipping procedures are simplified and
  standardized with unit cube

Translation factors
Ratios of the dimensions of the viewport and
view volume
5
Normalization Oblique Projection

• Oblique Projection
• Tan a z / (x x) gt x x z cot a, y y
  z cot b
• z 0
• P MorthoH(a,b) gt P MorthoSTH

6
Normalization Perspective View

• Perspective Projection
• Perspective transformation Orthographic
  projection

7
Normalization Perspective View

• Cosider Z
• Applied CCV
• Each range -1 1
• Z -1