Posts Tagged ‘PowerVR’

VBO (Vertex Buffer Object) Limitations on iOS Devices

Posted: July 10, 2011 by Kearwood Gilbert in Programming
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With the iPhone 3GS, the iOS platform gained programmable shader support through the PowerVR SGX 535.  Accompanied with an increase from 2 to 8 texture units, artists and developers have limitless creative expression by using any material in their 3d scenes that they can describe in GLSL.  The unsung hero of these upgraded GPU’s are their “real” Vertex Buffer Objects (VBO).

Vertex Buffer Objects allow the vertex level data to be moved from slower main memory to memory that can be accessed more rapidly by the GPU.  Instead of making a separate GL call to render each polygon, the VBO’s can be initialized when a model is loaded and a single GL call instructs the GPU to iterate through the vertices and rendering polygons is performed by the GPU.  Even though the new IOS platforms have a UMM (Unified Memory Model) where the CPU and GPU share the same ram chips and bus, utilizing VBO’s frees up the ARM CPU core during rendering for other game pipeline tasks such as physics calculation, AI, and audio.