array UBO members need to be 16-bytes-aligned to avoid implicit padding

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This is because GPUs access data in memory in chunks of 16 bytes, known as a "cache line." If a UBO member is not 16-bytes-aligned, the GPU may need to perform additional memory accesses to fetch the data, which can slow down performance. By ensuring that UBO members are 16-bytes-aligned, we can optimize memory access and improve performance.