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If your application uses the fixed-function pipeline, a critical task is to replace those tasks with shaders. In contrast, configuring the fixed-function pipeline incurs significant function-call overhead. Your application can switch between different shaders with a single function call. Because you have extensive control over the pipeline, it is also easier to implement multipass algorithms without requiring the data to be read back from the GPU. Shaders allow for longer and more complex algorithms to be implemented using a single rendering pass. The fixed function pipeline is itself implemented as a shader. Older graphics processors implemented the fixed-function pipeline in hardware or microcode, but now graphics processors are general-purpose computing devices.
Opengl 4.1 create shader pipelines code#
Rather than writing complex blocks of configuration calls to implement a mathematical operation, you write code that expresses the algorithm directly. Shaders allow for algorithms to be written in a terse, expressive format.
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Shaders give you precise control over the operations that are performed to render your images. Shaders offer a considerable number of advantages to your application: Figure 12-2 shows where your applications can hook into the pipeline with shaders. This program is compiled by OpenGL and uploaded directly into the graphics hardware. A shader is a program written in a special shading language.
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Starting with OpenGL 2.0, some stages of the OpenGL pipeline can be replaced with shaders. Figure 12-1 OpenGL fixed-function pipeline Extensions offered new configuration options, but did not change the complex nature of OpenGL programming. Complex algorithms required multiple rendering passes and dozens of function calls to configure the calculations that the programmer desired. To configure the various stages of the pipeline shown in Figure 12-1, applications called OpenGL functions to tweak the calculations that were performed for each vertex and fragment. OpenGL 1.x used fixed functions to deliver a useful graphics pipeline to application developers. Customizing the OpenGL Pipeline with Shaders To create high-performance code on GPUs, use the Metal framework instead.