Currently there is no clear way to know if an operation is constant
(i.e. when all rendered pixels have same values). Operations may
need to get constant input values before rendering to determine
their resolution or areas of interest. This is the case of scale, rotate
and translate operations. Only "set operations" are known as
constant but many more are constant when all their inputs are so.
Such cases can be optimized by only rendering one pixel.
Current solution for tiled implementation is to get first pixel
from input. This works for root execution groups, others
need previous groups to be rendered.
On full frame implementation this is not possible, because buffers
are created on rendering to reduce peak memory and there is
no per pixel calls.
This patch evaluates all operations that are constant into primitive
operations (Value/Vector/Color) before determining resolutions.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D11490
This patch adds the base code needed to make the full-frame system work for both current tiled/per-pixel implementation of operations and full-frame.
Two execution models:
- Tiled: Current implementation. Renders execution groups in tiles from outputs to input. Not all operations are buffered. Runs the tiled/per-pixel implementation.
- FullFrame: All operations are buffered. Fully renders operations from inputs to outputs. Runs full-frame implementation of operations if available otherwise the current tiled/per-pixel. Creates output buffers on first read and free them as soon as all its readers have finished, reducing peak memory usage of complex/long trees. Operations are multi-threaded but do not run in parallel as Tiled (will be done in another patch).
This should allow us to convert operations to full-frame in small steps with the system already working and solve the problem of high memory usage.
FullFrame breaking changes respect Tiled system, mainly:
- Translate, Rotate, Scale, and Transform take effect immediately instead of next buffered operation.
- Any sampling is always done over inputs instead of last buffered operation.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D11113
