Using one buffer containing matrices for several objects and one descriptor of VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC type to access different parts of the buffer.
We want to draw three triangles, but in different positions, so we need to load different matrices for each triangle.
We have two simple options:
1: Use three different buffers(one per matrix) and three different descriptors(one per buffer).
2: Use one buffer which will contain three matrices and use three descriptors which will refer to different offsets in the buffer. These offsets have to be specified when writing the descriptor (in the VkDescriptorBufferInfo structure).
These two options have disadvantages: (1) creating a lot of buffers is not good from performance point of view. (2) creating many descriptors for just one buffer is not good either, moreover we would have to overwrite the descriptor set to change the offsets.
In Vulkan it is possible to create one descriptor with type VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC which allows you to refer to one buffer, but by specifying the offset in it.
The base offset calculated by the VkDescriptorBufferInfo when initially updating the descriptor set is added to a dynamic offset when binding the descriptor set.
The only thing to consider is that the value of the dynamic offset must be a multiple of the minUniformBufferOffsetAlignment value from the device limits, since the GPU cannot read from any offset.
