LargeScale Polygon Rendering Solutions n n Decimation Visibility

Large-Scale Polygon Rendering

Solutions n n Decimation Visibility Culling Parallel Rendering Others

Surface Decimation Use a smaller number of triangles to represent the same surface -> preserve the topology Removing vertices Contracting edges Etc.

Visibility Culling Do not display polygons that are not visible to the eyes 1 million triangles 188, 000 triangles

Parallel Rendering

3 D Rendering Pipeline Transformation Clipping (modeling, viewing, projection) Lighting Z-buffer Screen Projection Shading Scan conversion Geometry Processing Rasterization

Parallel Rendering sequential G R display fully parallel G G G R R R display

Parallel Rendering (2) n n Geometry processing: parallelized by assigning each processor a subset of primitives (polygons) Rasterization: parallelized by assigning each processor a portion of pixel calculations

Parallel Rendering (3) What is rendering anyway? Calculate the effect of each primitive on each pixel During transformation, a primitive can go anywhere on the screen Rendering can be seen as sorting primitives to the screen

Parallel Rendering (4) Rendering as a sorting process

Sorting primitives Where to sort? Sorting can pretty much happy anywhere Where/When to sort will affect the structure of the parallel rendering system G G G R R R display

Sort-First Parallel Rendering

Sort-First Parallel Rendering Distribute the primitives early in the rendering pipeline P 1: P 1 P 2 P 3 P 4 P 2: 1. 2. 3. 4. 5. 5. 6. Subdivide the screen “Pre-transform” the primitives Distribute the primitives Each processor render its own primitives No communication needed afterwards P 3: P 4:

Sort-Middle Parallel Rendering

Sort-Middle Parallel Rendering Distribute the primitives in the middle of pipeline 1. Arbitrary assignment P 1: P 2: P 3: P 4: 2. Geometry processing 3. Sorting P 1 P 2 P 3 P 4 Rasterization

Sort-Last Parallel Rendering

Sort-Last Parallel Rendering Distribute the primitives in the end of pipeline 1. Arbitrary assignment P 1: P 2: P 3: P 4: 2. Geometry processing 3. Rasterization P 1 P 2 P 3 P 4 G G R R

Sort-Last Parallel Rendering P 1 P 2 P 3 P 4 Sort images with z Compositing/z-buffer P 1 P 2 P 3 P 4