RealityEngine Graphics

1. RealityEngine Graphics Kurt Akeley Silicon Graphics Computer Systems

2. Overview • Introduction • System Architecture • Features • Conclusions / Results

3. Introduction • SGI created. • High end graphics work station • Hardware Solution

4. Introduction • First Generation System • Made in the early 80s • Useful hardware was just becoming available • Floating Point hardware • No Frame-buffer Memory • No ASICs • Lack of Functionality other than transformation.

5. Introduction • First Generation System • Target • Transformation • Flat-Shaded Primitives • Results • Very simple scenes

6. Introduction • Second Generation Systems • Made in the late 80s • Useful hardware was available and affordable • Frame buffers • ASICs • Greater Functionality

7. Introduction • Second Generation System • Target • Interpolate Color and Depth • Good Performance • Solid or Wire frame images • Results • More complex scenes

8. Introduction • RealityEngine (Third Generation) • Made in the 90s • Hardware is cheap • More functionality

9. Introduction • RealityEngine • Target • ½ Million triangles • Filtered Textures • Antialiasing • 30Hz rendering for full screen • 800000 triangles per second

10. Architecture • Overview System Bus Geometry Board Triangle Bus Raster Memory Boards Display Gen Board

11. Architecture • Geometry Board • Input FIFO • Command Processor • Geometry Engines Command Processor GE GE GE GE

12. Architecture • Command Processor • Two kinds of Commands • Frequent • Infrequent • Breaks down commands • Broadcasts commands to Geometry Engines

13. Architecture • Geometry Engine • Transforms, Lights, Clips polygons • Decomposes all polygons to triangles. • Setups a plane equation in X,Y screen directions

14. Architecture • Triangle Bus • Used to broadcast output from Geometry Engines • Huge in size to prevent bottlenecking.

15. Architecture • Raster Memory Boards • 5 Fragment Generators • 80 Image Engines • Huge Framebuffer FG FG FG FG FG

16. Architecture • Fragment Generator • Fragments • Coverage Mask • Texture Controls • Color • Fog

17. Architecture • Fragment Generator • Fragment Generation • Uses Modified Pineda algorithm • Coverage Mask Generation • Generates 8x8 Masks

18. Architecture • Fragment Generator • Texture Control • Based around the most center pixel in mask. • LOD Fraction and the center pixels location determine texel location.

19. Architecture • Fragment Generator • Blends texture color with fragment color • Blends Fog

20. Architecture • Image Engine • Each engine is responsible for X pixels. • Reconstructs subpixel sample depth using XY slopes. • Update the framebuffer.

21. Architecture • Display Gen Board • Each Image Generator pass on color • Board dithers 12 bits to 10 bits. • Gamma Corrects

22. Features • Antialiasing • Alpha • Determine alpha scale factor for blending. • Poor results with polygons • Multisample • Two Mask Generation Modes • Point Sampled • Area Sampled

23. Features • Texture Mapping • 2D Textures • Mipmapped • 3D Textures • LOD texture mapping • Filtering • Magnification

24. Features • Stereo in a Window • Fast Clipping • Expand the frustum • Scissor

25. Conclusions / Results • Design Alternatives • Single-Pass Antialiasing • Improve resolution through hardware • Multisample Antialiasing • Brute Force vs. Finese • Immediate Resolution of Multisample Color • Use fragment color most of the time.

26. Conclusions / Results • Design Alternatives • Triangle Bus • 12-bit Color vs 8-bit • Visual banding elimination • Degraded resolution

27. Conclusions / Results • Results • Created a System that could • 20-60 Hz display system • Handle advanced functionality

28. RealityEngine Current Pipeline Conclusion Application Vertex Program Rasterization Fragment Program Display