1. Pipeline Optimization Real-Time Rendering 2002. 5. 22 김 송 국

2.  Optimization  Application Stage  Geometry Stage  Rasterizer Stage  Overall Optimization  Locating the Bottleneck  Testing the Application Stage  Testing the Geometry Stage  Testing the Rasterizer  Balancing the Graphics Pipeline  Host and Accelerator  Multiprocessing  Multiprocessor Pipelining  Parallel Processing Content

3.  Three Conceptual Stage  Application, Geometry, and Rasterizer  Based on a pipelined architecture  One of these stages will always be the bottleneck  A prime candidate for optimization  Optimizing the performance of the rendering pipeline ; process of optimizing a pipeline processor (CPU) i) Bottleneck of the pipeline is located ii) Optimized in someway  Two stage become the bottleneck again

4. Locating the Bottleneck  The first step in optimizing a pipeline  Not easily done Simply by timing the process  Another approach would be to clock the individual stages (set up a number of test)  Each test only affects one stage at a time Testing the Application Stage Testing the Geometry Stage Testing the Rasterizer Stage

5. Testing the Application Stage  Test for CPU limits  Measuring the workload on the CPU processor(s)  Does not change the workload on the CPU  Send down data that causes the other stages to do little or no work Ex) OpenGL Replacing all glVertex3fv+ and glNormal3fv call with glColor3fv calls

6. Testing the Geometry Stage  Most difficult stage to test  Workload on this stage is changed  The workload on one or both of the other stages is often changed  Type and number of light sources

7. Testing the Rasterizer Stage  The easiest and fastest to test  Simply decrease the resolution of the window  Not affect the application stage or the geometry stage

8. Optimization  Optimize that stage to boost the performance  Optimizations trade off quality for speed

9. Optimization (1)Application Stage  Techniques of the Two Optimization ; Making the code and the memory accesses  Making the Code  The basic rule of optimization to try a variants ; Reexamine algorihms, assumptions, and code syntax, trying as many variants as possible  Write the fastest code (Limit the user's ability)  Memory Accesses ; Memory accesses of the program faster

10. Optimization (1)Application Stage  Code Issues  Avoid using division as much as pollible  Unroll small loops in order to get rid of the loop overhead  Math functions are expensive and should be used with care  Use inline code for small functions that are frequently called  Lower floating-point precision when reasonable  Use const whenever possible

11. Optimization (1)Application Stage  Memory Issues  Memory that is accessed sequentially in the code ; Stored sequentially in the memory  Try to exploit the cache(s) of the architecture  Cache prefetching  Avoid pointer indirection, jumps, and function calls

12. Optimization (2)Geometry Stage  Responsible for Transforms, Lighting, Clipping, Projection and Screen Mapping  Process that can be optimized relatively easily  Transforms & Lighting  Memory Accesses ; Memory accesses of the program faster

13. Overall Optimization  Reduce the total number of drawing primitives  Choose as low a precision as is possible  Preprocess the models for redering in your prrtioular context  Turn off feature not in use  Minimize state changes by grouping objects (texture, material, lighting, transparency, etc.)  Spparate two-dimensional from three-demensional operations  Call glGet() during the set-up phase and avoid it during runtime

14. 8.3 Balancing the Graphics Pipeline 8.4 Host and Accelerator 8.5 Multi processing 8.5.1 Multiprocessor pipelining 8.5.2 Parallel Processing