Another thought on multi-threaded scan-line rasterization would be to pre-scan the node tree and pre-rasterize all
shapes into masks before we run through and render them to the destination. Again, that would be outside the scope of
9, but it would be a change only to the rendering process (and dealing with the caching of alpha masks) that would
leverage your ability to create multiple Marlin contexts without any changes to MarlinFX...
...jim
On 11/10/16 5:13 AM, Laurent Bourgès wrote:
Jim,
I would think an effort to parallelize a single shape rasterization would
be much simpler in scope. Still outside
the current JDK 9 timeline, but definitely something that could help in
future releases. I believe that once we put
the edges into the internal structures we could parallelize the
rasterization of individual scanlines and maybe
break a tall shape up into N horizontal bands for N threads. Other
thoughts would be a thread to generate the
crossings and N threads to populate the alphas...?
Multithreaded rendering is a complex task that should be discussed in another
thread as it is totally out of my current
scope.
My 2 cents: there is two approach:
- render shapes in parallel (but it requires the JavaFX pipeline to be
parallelized = tricky as caching mask, gpu need
single thread communication ...)
- render shape with several threads (as you proposed) but the scanline
algorithm requires the previous scanline
information like previous edges (so it becomes tricky to make it efficient) and
this will only speed up large shapes
(point clouds will remain slow !)
Anyway the major issue concerns latency ie how to spread the workload on
several threads when the scene contains shapes
with various sizes or complexity (edge count): the latency corresponds to the
slowest thread to complete its rendering task.
=> adaptive algorithm to make a sort of load balancing (work stealing approach)
or small tasks (average same cpu cost).
PS: I have some experience on parallelization, but please let's postpone this
discussion or let's do it in another thread.
Laurent
