Fix for #36468, "Buffer Groups" option changes compositing output

https://projects.blender.org//tracker/?func=detail&atid=498&aid=36468&group_id=9

Problem is that the read/write buffer operations only work with actual image inputs. If a singular value is used as group input no actual buffer will be created, the write operation does not schedule any chunks and the ReadBufferOperation subsequently returns zero (MemoryBuffer::read).

The fix uses the (0,0) resolution to detect single value input of the WriteBufferOperation. The actual resolution is then clamped to (1,1) to ensure we have a single pixel to store the value in. A m_single_value flag is also set, so we can reliably distinguish this from genuine image resolutions without having to check m_width/m_height later on.

The ReadBufferOperation copies this flag from the associated WriteBufferOperation and if set will always return the single value from pixel (0,0).

[jbkkavt, 2013-08-17 14:55:54]

On 2013/08/15 06:25:43, lukas.toenne1 wrote:

I got the issue, but not sure if we have introduced other issues with this fix.
opencl buffers are currently not checked on their dimensions.
The specs say it should work, as long as the right samplers are used.

Jeroen

[jbkkavt, 2013-08-17 14:56:26]

On 2013/08/17 14:55:54, jbkkavt wrote:
> On 2013/08/15 06:25:43, lukas.toenne1 wrote:
> 
> I got the issue, but not sure if we have introduced other issues with this
fix.
> opencl buffers are currently not checked on their dimensions.
> The specs say it should work, as long as the right samplers are used.
> 
> Jeroen

We will need to find a way to test this.