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OpenGL Insights by Christophe Riccio, Patrick Cozzi

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V
Transfers
OpenGL applications transfer a lot of data. Data is transferred between machines,
between disk and system memory, between system and video memory, between video
memory and video memory, and so on. Optimizing these transfers improves perfor-
mance. In this section, we look at optimizing asynchronous transfers between the
CPU and GPU; compressing models for u se with WebGL; compressing textures on
the GPU for video creation; and an efficient geometry file format.
Although general computations like particle systems are being pushed to the
GPU, there is still a need to do many computations or IO on the CPU and then
efficiently stream data to the GPU. In Chapter 28, Asynchronous Buffer Transfers,”
Ladislav Hrabcak and Arnaud Masserann share best practices for maximizing per-
formance when using buffer objects to transfer data between the CPU and GPU
in either direction. With detailed performance analysis, they cover direct memory
access (DMA), buffer usage hints, implicit synchronization with draw calls, pinned
memory, and multithreading. Shalini Venkataraman continues the asynchronous
transfers discussion in the following chapter, “Fermi Asynchronous Texture Trans-
fers,” where she discusses how the NVIDIA Fermi architecture allows transfer and
rendering to occur at the same time when using multiple threads and OpenGL
contexts.
The discussion of transfers moves from within a system to across systems in
Chapter 30, “WebGL Models: End-to-End.” Won Chun presents the techniques,
including a detailed analysis, used in Google Body to compress and transfer mod-
els to a web browser for rendering with WebGL. Continuing on the compression
theme, Brano Kemen demonstrates real-time image compression on the GPU in
Chapter 31, “In-Game Video Capture with Real-Time Texture Compression.” He
applies his method to video compression using a DXT fixed-rate compression format
389
390 V Transfers
to reduce bandwidth consumption, and he explores various decoloration methods to
enhance image compression quality.
In graphics, content is king. A smooth content-creation pipeline empowers
artists, and a format that requires minimal runtime processing improves load times.
In the last chapter of this section, “An OpenGL Friendly Geometry File Format and
its Maya Exporter,” Adrien Herubel and Venceslas Biri present the Drone format, a
binary geometry file format suitable for use with OpenGL.

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