Push Constant / Uniform Buffer

The minimum push constant that Vulkan can guarantee is 128 bytes. So if you want to make sure your Vulkan engine can work on all device/platform, then don’t exceed this number.

One mat4 is 16 floats, one float is 4 bytes, so one mat4 will use 64 bytes. 128 bytes = 2 * mat4

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Uniform buffer

Uniform buffer is a way to provide arbitrary read-only data to out shaders
(push constants is limited to the size, only 2 mat4 is allowed)
Disadvantages:

• reading from uniformbuffer memory can be slower
• require additional setup (buffer + descriptor sets)