1. cs4995-1 2/11/2003 Page 1 Special Image Effects Particle Systems Fog Lens Flares Shadows Programmable Shaders

2. cs4995-1 2/11/2003 Page 2 Particle Systems Each particle is a point, line, or textured polygons (with transparency). Polygons can be oriented to always face the viewpoint (fire, water spray, explosions, weapon fire, etc.) Or textured onto surfaces (splats) Usually thousands of particles are used

3. cs4995-1 2/11/2003 Page 3 Particle Systems Particle Source Particle Attributes (can be static or functional) –Position –Velocity (speed and direction) –Color –Lifetime –Age –Shape –Size –Transparency Shape Point

4. cs4995-1 2/11/2003 Page 4 Particle Systems Simple concept, simple to implement… However, a good implementation requires some careful thought and consideration since you need to dynamically manage thousands of objects.

5. cs4995-1 2/11/2003 Page 5 Particle Systems Some links – Particle Systems by Allen Martin http://www.cs.wpi.edu/~matt/courses/cs563/talks/psys.html – Gammasutra: Building an Advanced Particle System http://www.gamasutra.com/features/20000623/vanderburg_01.htm – Particle Systems API http://www.cs.unc.edu/~davemc/Particle/ (demo taken from here)

6. cs4995-1 2/11/2003 Page 6 Fog Function of distance from the camera (linear or exponential) –as distance increases, bring colors to grey Can be done just with Z-buffer Also can be used to reduce scene complexity Same idea can be used to fade far objects in and out (prevents flickering)

7. cs4995-1 2/11/2003 Page 7 Fog example 1 MechWarrior 4: Mercenaries

8. cs4995-1 2/11/2003 Page 8 Fog example 2

9. cs4995-1 2/11/2003 Page 9 Billboard objects Textured polygons that rotate to stay flat towards the eye. Used often for trees, trees, clouds, smoke, explosions, lens effects, etc. Red Faction 3 - PC Another way to do trees, bushes, telephone poles, etc. without reorienting polygons each frame

10. cs4995-1 2/11/2003 Page 10 Lens Effects Billboards at varying levels of depth. Usually rendered last. Sometimes just an overlay on the screen. From http://www.geocities.com/SiliconValley/Lakes/1434/lenseffects.htmlhttp://www.geocities.com/SiliconValley/Lakes/1434/lenseffects.html

11. cs4995-1 2/11/2003 Page 11 Lens animation

12. cs4995-1 2/11/2003 Page 12 Lens Effects – Asheron’s Call 2 Asheron’s Call 2

13. cs4995-1 2/11/2003 Page 13 Shadows Projected shadows on flat surfaces (project polygon onto surface)

14. cs4995-1 2/11/2003 Page 14 Soft Shadows Multiple light sources or area sources give soft shadows (umbra, penumbra) penumbra umbra penumbra umbra

15. cs4995-1 2/11/2003 Page 15 Soft Shadows From http://www.stereopsis.com/shadow/http://www.stereopsis.com/shadow/

16. cs4995-1 2/11/2003 Page 16 Shadow Volumes

17. cs4995-1 2/11/2003 Page 17 Programmable Shaders Renderman was the first programmable shading language DirectX 8 featured vertex and pixel shaders Nvidia and ATI boards now have programmable shading capabilities

18. cs4995-1 2/11/2003 Page 18 Direct3D Pipeline

19. cs4995-1 2/11/2003 Page 19 Shaders Vertex Shaders: –procedural geometry deformation –range-based or radial fog effects –camera lens effects including fish eye, wide angle, and water refraction effects. Pixel Shaders: –per-pixel reflections –per-pixel lighting using Phong-style shading or DOT3 effects –procedural textures

20. cs4995-1 2/11/2003 Page 20 Cg Vertex Shader Examples Anisotropic Lighting Fog

21. cs4995-1 2/11/2003 Page 21 Cg Vertex Shader Examples Stencil Shadow Volumes Refract Reflect Demo

22. cs4995-1 2/11/2003 Page 22 Cg Pixel Shader Examples Soft Stencil ShadowsHardware Shadow Maps

23. cs4995-1 2/11/2003 Page 23 Cg Pixel Shader Examples Water Interaction Flare

24. cs4995-1 2/11/2003 Page 24 Cg Shader Examples Fire http://www.cgshaders.org/shaders/show.php?id=39 Shadow volumes w/fog http://www.cgshaders.org/shaders/show.php?id=49