derive sorting_buffer_size from cloud count (with possible rounding to next powe...

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https://api.github.com/mosure/bevy_gaussian_splatting/blob/eedd27e0f32bdf33f324238284c915dc6e1574d2/src/render/mod.rs#L184

        gaussian_cloud: Self::ExtractedAsset,
        render_device: &mut SystemParamItem<Self::Param>,
    ) -> Result<Self::PreparedAsset, PrepareAssetError<Self::ExtractedAsset>> {
        let gaussian_buffer = render_device.create_buffer_with_data(&BufferInitDescriptor {
            label: Some("gaussian cloud buffer"),
            contents: bytemuck::cast_slice(gaussian_cloud.0.as_slice()),
            usage: BufferUsages::VERTEX | BufferUsages::COPY_DST | BufferUsages::STORAGE,
        });

        let count = gaussian_cloud.0.len() as u32;

        // TODO: derive sorting_buffer_size from cloud count (with possible rounding to next power of 2)
        let sorting_global_buffer = render_device.create_buffer(&BufferDescriptor {
            label: Some("sorting global buffer"),
            size: ShaderDefines::default().sorting_buffer_size as u64,
            usage: BufferUsages::STORAGE | BufferUsages::COPY_DST | BufferUsages::COPY_SRC,
            mapped_at_creation: false,
        });

        let draw_indirect_buffer = render_device.create_buffer(&BufferDescriptor {
            label: Some("draw indirect buffer"),
            size: std::mem::size_of::<wgpu::util::DrawIndirect>() as u64,
            usage: BufferUsages::INDIRECT | BufferUsages::COPY_DST | BufferUsages::STORAGE | BufferUsages::COPY_SRC,
            mapped_at_creation: false,
        });

        let sorting_pass_buffers = (0..4)
            .map(|idx| {
                render_device.create_buffer_with_data(&BufferInitDescriptor {
                    label: format!("sorting pass buffer {}", idx).as_str().into(),
                    contents: &[idx as u8, 0, 0, 0],
                    usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
                })
            })
            .collect::<Vec<Buffer>>()
            .try_into()
            .unwrap();

        let entry_buffer_a = render_device.create_buffer(&BufferDescriptor {
            label: Some("entry buffer a"),
            size: (count as usize * std::mem::size_of::<(u32, u32)>()) as u64,
            usage: BufferUsages::STORAGE | BufferUsages::COPY_SRC,
            mapped_at_creation: false,
        });

        let entry_buffer_b = render_device.create_buffer(&BufferDescriptor {
            label: Some("entry buffer b"),
            size: (count as usize * std::mem::size_of::<(u32, u32)>()) as u64,
            usage: BufferUsages::STORAGE | BufferUsages::COPY_SRC,
            mapped_at_creation: false,
        });

        Ok(GpuGaussianCloud {
            gaussian_buffer,
            count,
            draw_indirect_buffer,
            sorting_global_buffer,
            sorting_pass_buffers,
            entry_buffer_a,
            entry_buffer_b,
        })
    }
}