# Objective
This is a minimally disruptive version of #8340. I attempted to update
it, but failed due to the scope of the changes added in #8204.
Fixes#8307. Partially addresses #4642. As seen in
https://github.com/bevyengine/bevy/issues/8284, we're actually copying
data twice in Prepare stage systems. Once into a CPU-side intermediate
scratch buffer, and once again into a mapped buffer. This is inefficient
and effectively doubles the time spent and memory allocated to run these
systems.
## Solution
Skip the scratch buffer entirely and use
`wgpu::Queue::write_buffer_with` to directly write data into mapped
buffers.
Separately, this also directly uses
`wgpu::Limits::min_uniform_buffer_offset_alignment` to set up the
alignment when writing to the buffers. Partially addressing the issue
raised in #4642.
Storage buffers and the abstractions built on top of
`DynamicUniformBuffer` will need to come in followup PRs.
This may not have a noticeable performance difference in this PR, as the
only first-party systems affected by this are view related, and likely
are not going to be particularly heavy.
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## Changelog
Added: `DynamicUniformBuffer::get_writer`.
Added: `DynamicUniformBufferWriter`.
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