General Tips for Performance Improvement

• Fill-rate limited applications. Because per-primitive operations (transformations, lighting, and so on) are very efficient on Indigo2 IMPACT systems, applications may find that they are fill-rate limited when drawing large polygons (more than 50 pixels per triangle). In that case, you can actually increase the complexity of per-primitive operations at no cost to overall performance. For example, additional lights or two-sided lighting may come for free.

  For general advice on improving performance for fill-rate limited applications, see "Tuning the Raster Subsystem". Specific for Indigo2 IMPACT systems is that texturing is optimized.

• Geometry-limited applications. For applications that draw many small polygons, consider a different approach: Use textures to avoid drawing so many triangles. See "Using Textures".

• Clipping. For optimum performance, avoid clipping. Special hardware supports clipping within a small range outside of the viewport. By keeping geometry within this range, you may be able to significantly reduce clipping overhead.

• GLU NURBS. If you use GLU NURBS, store the tessellation result in display lists to take full advantage of evaluator performance. Don't for example, recompute tessellations.

• Antialiasing. Antialiased lines on Indigo2 IMPACT systems are high quality and fast. Applications that did not use antialiased lines before because of the performance penalty may now be able to take advantage of them. All antialiased lines are rendered with the same high quality, regardless of the settings of GL_LINE_SMOOTH_HINT. Although available, wide antialiased lines are not supported in hardware and should be avoided. Wide antialiased points are supported in hardware with good performance.

  Multisampling is not supported. Antialiasing of polygons is not supported in hardware. You can, however, draw antialiased line loops around polygons to get antialiasing.