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Guidelines

You'll want to keep the following in mind when you set up full scene anti-aliasing:

• Although a system may have enough VRAM to accommodate a multisample buffer, a large buffer can affect the ability of OpenGL to maintain a properly working texture set. Keep in mind that the buffers associated with the rendering context—depth and stencil—increase in size by a factor equal to number of samples per pixel.

• The OpenGL driver allocates the memory needed for the multisample buffer; your application should not allocate this memory.

• Any anti-aliasing algorithm that operates on the full scene requires a fair amount of computing resources. In some cases, there is a tradeoff between performance and quality. For that reason, developers sometimes provide a user interface element that allows the user to enable and disable FSAA, or to choose the level of quality for anti-aliasing.

• The commands glEnable(GL_MULTISAMPLE) and glDisable(GL_MULTISAMPLE) are ignored on some hardware because some graphics cards have the feature enabled all the time. That doesn't mean that you should not call these commands because you'll certainly need them on hardware that doesn't ignore them.

• A hint as to the variant of sampling you want is a suggestion, not a command. Not all hardware supports all types of anti-aliasing. Other hardware mixes multisampling with supersampling techniques. The driver dictates the type of anti-aliasing that's actually used in your application.

• The best way to find out which sample modes are supported is to call the CGL function CGLDescribeRenderer with the renderer property kCGLRPSampleModes or kCGLRPSampleAlpha.

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