From 48bc79fb68d0fedd367ee8e0abfe504272c6743f Mon Sep 17 00:00:00 2001
From: Eric Mehl <eric@thinkhypothetical.com>
Date: Wed, 22 Nov 2023 17:16:34 -0500
Subject: [PATCH] LightPositionTool : Handle multiple selected lights (WIP)

---
 .../LightPositionToolTest.py                  | 56 +++++++++++++++++++
 src/GafferSceneUI/LightPositionTool.cpp       | 22 +++++++-
 2 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/python/GafferSceneUITest/LightPositionToolTest.py b/python/GafferSceneUITest/LightPositionToolTest.py
index ce7ad806831..eeb40c5f9ce 100644
--- a/python/GafferSceneUITest/LightPositionToolTest.py
+++ b/python/GafferSceneUITest/LightPositionToolTest.py
@@ -44,6 +44,7 @@
 
 import Gaffer
 import GafferUITest
+import GafferScene
 import GafferSceneUI
 import GafferSceneTest
 
@@ -99,6 +100,61 @@ def testPosition( self ) :
 			for j in range( 0, 3 ) :
 				self.assertAlmostEqual( o[j] % 360, math.degrees( rotationO[j] ) % 360, places = 3 )
 
+	def testMultiple( self ) :
+
+		script = Gaffer.ScriptNode()
+
+		script["group"] = GafferScene.Group()
+
+		i = 0
+		positions = [ imath.V3f( 1, 1, 0 ), imath.V3f( 1, -1, 0 ), imath.V3f( -1, -1, 0 ), imath.V3f( -1, 1, 0 ) ]
+		for p in positions :
+			n = "light" + str( i )
+			script[n] = GafferSceneTest.TestLight()
+			script[n]["name"].setValue( n )
+			script[n]["transform"]["translate"].setValue( p )
+
+			script["group"]["in"][i].setInput( script[n]["out"] )
+
+			i += 1
+
+		view = GafferSceneUI.SceneView()
+		view["in"].setInput( script["group"]["out"] )
+		GafferSceneUI.ContextAlgo.setSelectedPaths(
+			view.getContext(),
+			IECore.PathMatcher( [ "/group/light{}".format( i ) for i in range( 0, 4 ) ] )
+		)
+
+		tool = GafferSceneUI.LightPositionTool( view )
+		tool["active"].setValue( True )
+
+		tool.handlesTransform()  # Trigger `updateHandles()` to update our centroid
+
+		shadowPivot = imath.V3f( 0, 1, 0 )
+		shadowPoint = imath.V3f( 0, 0, -1 )
+		tool.position( shadowPivot, shadowPoint )
+
+		transform = imath.M44f().rotate( IECore.degreesToRadians( imath.V3f( -45, 0, 0 ) ) )
+		transform.translate( self.__shadowSource( imath.V3f( 0 ), shadowPivot, shadowPoint ) )
+
+		print( self.__shadowSource( imath.V3f( 0 ), shadowPivot, shadowPoint ) )
+
+		i = 0
+		for p in positions :
+			newP = script[n]["transform"]["translate"].getValue()
+			newR = script[n]["transform"]["rotate"].getValue()
+
+			self.assertAlmostEqual( newR.x, -45.0, places = 4 )
+			self.assertAlmostEqual( newR.y, 0.0, places = 4 )
+			self.assertAlmostEqual( newR.z, 0.0, places = 4 )
+
+			desiredP = p * transform
+			for j in range( 0, 3 ) :
+				with self.subTest( "Point {}, {} Axis".format( p, {0: "X", 1: "Y", 2: "Z"}.get( j ) ), j=j ) :
+					self.assertAlmostEqual( newP[j], desiredP[j], places = 4 )
+
+			i += 1
+
 	def testUndo( self ) :
 
 		script = Gaffer.ScriptNode()
diff --git a/src/GafferSceneUI/LightPositionTool.cpp b/src/GafferSceneUI/LightPositionTool.cpp
index 833ac5ff450..18d5fcb1937 100644
--- a/src/GafferSceneUI/LightPositionTool.cpp
+++ b/src/GafferSceneUI/LightPositionTool.cpp
@@ -104,7 +104,14 @@ void LightPositionTool::position( const V3f &shadowPivot, const V3f &shadowPoint
 		shadowPivot
 	;
 
-	const M44f centroidTransform = rotationMatrix( m_worldCentroid - shadowPivot, newCentroid - shadowPivot );
+	const M44f centroidPivotFrame = m_centroidOrientation.toMatrix44().translate( m_worldCentroid );
+
+	const V3f newDir = ( shadowPivot - newCentroid ).normalized();
+	const V3f newDirX = newDir.cross( V3f( 0, 1, 0 ) ).normalized();
+	const V3f newDirY = newDir.cross( newDirX ).normalized();
+	const M44f newFrame = computeLocalFrame( -newCentroid, newDirX, newDirY );
+
+	const M44f centroidTransform = centroidPivotFrame * newFrame.inverse();
 
 	UndoScope undoScope( selection().back().editTarget()->ancestor<ScriptNode>() );
 
@@ -175,7 +182,18 @@ void LightPositionTool::selectionChanged( const TransformTool &tool )
 			return;
 		}
 
-		m_worldCentroid = V3f( 0 ) * selection().back().orientedTransform( Orientation::World );
+		int count = 0;
+		for( const auto &s : selection() )
+		{
+			m_worldCentroid += V3f( 0 ) * s.orientedTransform( Orientation::World );
+			count ++;
+		}
+
+		m_worldCentroid /= count;
+
+		/// \todo Here we're just taking the orientation from the last selected object.
+		/// Is there a better way?
+		m_centroidOrientation = extractQuat( selection().back().orientedTransform( Orientation::World ) );
 	}
 }