CODEWITHSUNDEEP
mobilegraphicsopengl-esgpu
Zebrafish
Zebrafish

Reputation: 14424

The concept of 'sending' data to the GPU in OpenGL ES

Having only used Direct3D and OpenGL on desktop computer, I have this concept in my head that whenever buffers need to be updated you need to send this data to the GPU with calls such as glBufferData()/glBufferSubData(), and that this type of thing should be minimised at all costs.

Since OpenGL ES works with embedded systems such as phones, and the devices I don't think have dedicated GPU RAM, I was wondering if such an API call does completely different things if compiled on one device (Android) vs on another device (Windows desktop computer). The calls seem the same or similar whether on OpenGL or OpenGL ES, and I was wondering if I write my program on Windows it'll work on a mobile device. My guess is that on a mobile device these function calls will load data onto the system RAM whereas on a desktop it will be sent to the GPU RAM, if a GPU is available.

If this is the case, then is it an advantage for the mobile device in that data is only kept in one place and never sent anywhere else (ie., to the GPU)?

Upvotes: 1

Views: 415

Answers (1)

solidpixel
solidpixel

Reputation: 12269

The only significant difference is that in one case there is a DMA transfer over PCIe (desktop), in the other case it's just a memcpy to a driver-owned buffer in system RAM (mobile).

In both cases it can be relatively expensive (e.g. memory allocation, data copy, and possibly a need for cache maintenance on some systems), so it should still be minimized whenever possible. It's far more efficient to upload resources to wherever they need to be at the start of a game level and then just reference them from then onwards.

Upvotes: 1

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