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Chapter 13 Special Visual Techniques

Chapter 13 Special Visual Techniques. Blending. Without blending, a source fragment’s color values are supposed to overwrite those of its destination pixel. With blending, the source fragment does not overwrite its destination pixel . Pay attention to the z-value (depth testing).

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Chapter 13 Special Visual Techniques

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  1. Chapter 13 Special Visual Techniques

  2. Blending • Without blending, a source fragment’s color values are supposed to overwrite those of its destination pixel. • With blending, the source fragment does not overwrite its destination pixel. • Pay attention to the z-value (depth testing). • Blending equation:

  3. Blending • Example: • source (0.6, 0.4, 0.2); dest (0.5, 0.5, 0.5) • SourceRb= SourceGb= SourceBb=0.3 • destRb= destGb= destBb=0.7 • Blending equation gives: • (0.3*0.5+0.7*0.6, 0.3*0.5+0.7*0.4, 0.3*0.5 +0.7*0.2) = (0.57, 0.43, 0.29)

  4. Blending

  5. Fog • Fog is an atmospheric effect that OpenGL offers ready to use. • glEnable(GL_FOG), glDisable(GL_FOG) • glFogfv(GL_FOG_COLOR, flgColor) • glFogi(GL_FOG_MODE, fogMode) • GL_LINEAR • GL_EXP • GL_EXP2

  6. Fog • GL_LINEAR: • GL_EXP: • GL_EXP2:

  7. Fog

  8. Antialiasing

  9. Antialiasing • Enable blending • Antialiasing itself is enabled with a call to • glEnable(GL_LINE_SMOOTH) • For the best possible antialiasing with the call • glHint(GL_LINE_SMOOTH_HINT, GL_NICEST)

  10. Environment Mapping • The goal of environment mapping is to simulate an object reflecting its surrounding, e.g., a shiny kettle reflecting the kitchen or a well-polished car reflecting the street. • Sphere Mapping • Cube Mapping

  11. Stencil Buffer Techniques • A stencil buffer is an extra buffer, in addition to the color buffer (pixel buffer) and depth buffer (z-buffering) found on modern graphics hardware. • Limit the area of rendering. • Make use of the strong connection between the depth buffer and the stencil buffer in the rendering pipeline. • Can put a heavy load on the graphics hardware.

  12. Bump Mapping • To give the illusion of geometric detail on a surface, e.g., making it appear ridged or dimpled, by means of perturbing the surface normals, but without actually changing any geometry.

  13. Raster Algorithms(Reading) • Cohen-Sutherland Line Clipper • Sutherland-Hodgeman Polygon Clipper • Bresenham line drawing • Polygon rasterizing

  14. Homework • Exercise 13.3

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