From fc5be0b59883c28d5d0702acb96dc3d72295dda8 Mon Sep 17 00:00:00 2001
From: Manuel Castilla <manzanillawork@gmail.com>
Date: Tue, 6 Jul 2021 16:16:08 +0200
Subject: Compositor: Constant folding

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
---
 .../compositor/operations/COM_SetVectorOperation.h | 35 +++++++++++++---------
 1 file changed, 21 insertions(+), 14 deletions(-)

(limited to 'source/blender/compositor/operations/COM_SetVectorOperation.h')

diff --git a/source/blender/compositor/operations/COM_SetVectorOperation.h b/source/blender/compositor/operations/COM_SetVectorOperation.h
index b444339fcb2..41fd06659d6 100644
--- a/source/blender/compositor/operations/COM_SetVectorOperation.h
+++ b/source/blender/compositor/operations/COM_SetVectorOperation.h
@@ -18,7 +18,7 @@
 
 #pragma once
 
-#include "COM_NodeOperation.h"
+#include "COM_ConstantOperation.h"
 
 namespace blender::compositor {
 
@@ -26,12 +26,14 @@ namespace blender::compositor {
  * this program converts an input color to an output value.
  * it assumes we are in sRGB color space.
  */
-class SetVectorOperation : public NodeOperation {
+class SetVectorOperation : public ConstantOperation {
  private:
-  float m_x;
-  float m_y;
-  float m_z;
-  float m_w;
+  struct {
+    float x;
+    float y;
+    float z;
+    float w;
+  } vector_;
 
  public:
   /**
@@ -39,37 +41,42 @@ class SetVectorOperation : public NodeOperation {
    */
   SetVectorOperation();
 
+  const float *get_constant_elem() override
+  {
+    return reinterpret_cast<float *>(&vector_);
+  }
+
   float getX()
   {
-    return this->m_x;
+    return vector_.x;
   }
   void setX(float value)
   {
-    this->m_x = value;
+    vector_.x = value;
   }
   float getY()
   {
-    return this->m_y;
+    return vector_.y;
   }
   void setY(float value)
   {
-    this->m_y = value;
+    vector_.y = value;
   }
   float getZ()
   {
-    return this->m_z;
+    return vector_.z;
   }
   void setZ(float value)
   {
-    this->m_z = value;
+    vector_.z = value;
   }
   float getW()
   {
-    return this->m_w;
+    return vector_.w;
   }
   void setW(float value)
   {
-    this->m_w = value;
+    vector_.w = value;
   }
 
   /**
-- 
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