This is also known as page-locked memory. Finally, pinned memory is a portion of the main RAM that can be directly used by the device through the PCI express bus (PCI-e). This matches the client/server paradigm of OpenGL. Data transfers from CPU memory to device memory will be consistently referred to as uploading and transfers from the device memory to CPU memory as downloading. This queue has already been refered to as the command queue, but in order to be clear, we refer to it as the device command queue. These commands are then consumed by the device asynchronously. Second, when calling OpenGL functions, the drivers translate calls into commands and add them into an internal queue on the CPU side. In this chapter, we will be using OpenGL 3.3, which is the Direct3D 10 equivalent.įirst, in order to match the OpenGL specification, we refer to the GPU as the device.
If an application needs to transfer meshes or textures frequently and efficiently, these methods can be used to improve its performance. In this chapter, for readers familiar with buffer objects, we are going to explain what happens in the drivers and then present various methods, including unconventional ones, to transfer data between the CPU and the GPU with maximum speed. Furthermore, the OpenGL API specification doesn’t tell how to do it efficiently, and a naive use of data-transfer functions wastes processing power on both the CPU and the GPU by introducing pauses in the execution of the program. While copying data back and forth to the GPU is easy, the PC architecture, without unified memory, makes it harder to do it fast. image histogram for computing HDR tonemapping parameters.page resolver pass in virtual texturing.Likewise, it is often useful to read generated data back from the GPU. setting uniform parameters for shaders with uniform buffers.updating skeletal and blend-shapes animations on the CPU.streaming data from hard drive or network: geometry, clipmapping, level of.Most 3D applications send large quantities of data from the CPU to the GPU on a regular basis.
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