Computer Graphics: Programming, Problem Solving, and Visual Communication Steve Cunningham California State University Stanislaus and Grinnell College PowerPoint Instructor’s Resource

High-Performance Graphics Techniques Making your graphics programs run more quickly

Many Kinds of Techniques Outside the OpenGL system –Modeling, culling, sequencing, approximation Inside the OpenGL system –Texture maps, compile geometry, level of detail, light management Advanced techniques –Shaders… Can be used for games or other applications

Modeling Techniques Reducing the complexity of a scene –Processing fewer polygons Backface culling Visibility culling –Level of detail Distance from the eye Attenuation (fog) Motion (moving objects are seen less clearly)

Using Lights Each light you use adds complexity to the computation in the scene Enable and disable lights as you draw a scene so that only lights that make a difference to an object are used when the object is drawn

Sequencing Techniques Avoiding the use of the depth buffer –Painter’s algorithm –Uses depth-from-eye ordering to determine drawing order Binary space partitioning –Determines order from the eye more simply

Approximation Particularly useful for collision detection Approximate object by bounding spaces –First level -- spheres easy to compute if two spheres intersect an alternative is axis-aligned boxes –Second level -- triangles first test is meeting the plane of the triangle second test is actual triangle intersection

Texture Techniques Add complexity to a scene with textures, not with modeling –Use multitextures and mip-mapping to make this even more effective Use texture techniques such as billboards to replace complex structures with very simple ones –This was discussed in the textures chapter

OpenGL Tools Compiling geometry –Compile complex geometric objects into display lists so there is less work for the system to do when the objects are displayed Use fog –Hides some details of objects so you can use simpler (and thus faster) objects at a distance