05-rasteriz

05-rasteriz - Lecture 6 Rasterization and Anti-aliasing...

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Lecture 6 Rasterization and Anti-aliasing
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Reading Further reading: • Foley et al. 3.17 • Hearn Baker (3/E). 4.17-18
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Lecture outline: 1. Introduction to Rasterization 2. Rasterization Algorithms 3. Introduction to Anti-aliasing 4. Anti-aliasing Concepts 5. Anti-aliasing in OGL
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[Levoy] [Levoy] This lecture Previous lecture Introduction to Rasterization alpha depth texture coordinates
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Introduction to Rasterization After Projection and Clipping, we have: Polygons (triangles) with screen coordinates Per-vertex information such as color (RGBA), depth (Z), texture coordinate, etc. Why Rasterization? Our screen is made up of pixels (picture element) We only have finite screen precision to show the continuous geometry next next lecture
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Introduction to Rasterization Rasterization: 1. It first select pixels on the screen that best covers the 2D continuous geometry 2. It then interpolate the per-vertex information for each selected pixel 3. Geometries include Points (see glPointSize ) Lines (see glLineWidth ) Triangles (or polygons) Bitmap (see glBitmap and glDrawPixels ), etc.
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Introduction to Rasterization Note: 1. The hardware (this part of the graphics hardware) is called “Rasterizer” 2. Rasterization is performed on 2D domain 3. SGI’s first machine series is called IRIS, namely Integrated Raster Imaging System, in early 90’.
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Rasterization Algorithms For Points (non-antialiased): Just a square
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Rasterization Algorithms For Circle or antialiased Points: We have Bresenham circle algorithm (see reference text book for detail) x c y c Equation of a circle : () ( ) 2 2 2 r y y x x c c = + y k -1 y k x k x k +1 d 2 d 1 x k y 2 = r 2 –x 2 y=r x=0 Only need to do one Quadrant or Octant (-y, -x) (y, -x) (x, -y) (x, y) (y, x) (-y, x) (-x, y) (-x, -y)
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Rasterization Algorithms For Lines: We have DDA ( Digital Differential Analyzer ) (see reference text book for detail) y = y 1 + m ( x – x 1 ) 0 m 1 y 1 x 1 k=0 k=1 k=2 y int = floor ( y 1 + k * m + ½ ) This is called DDA “Digital Differential Analyzer” Uses floating point and truncation to choose integer y as k ( x – x1 ) = { 0, 1, 2, … }.
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Rasterization Algorithms For Lines:
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This note was uploaded on 10/19/2009 for the course COMP 341 taught by Professor Qu,huamin during the Spring '09 term at HKUST.

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05-rasteriz - Lecture 6 Rasterization and Anti-aliasing...

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