From 2b93c91b00b7a05c17bd332b7bc819bb44840032 Mon Sep 17 00:00:00 2001
From: Anders Pistol <anders.pistol@doctorentertainment.com>
Date: Sun, 16 Jun 2024 12:05:20 +0200
Subject: [PATCH] Traktor: Improved applying terrain editing brush when editing
 at a grazing angle etc.

---
 code/Heightfield/Heightfield.cpp            | 23 +++++----
 code/Terrain/Editor/TerrainEditModifier.cpp | 54 +++++++++++++++------
 2 files changed, 54 insertions(+), 23 deletions(-)

diff --git a/code/Heightfield/Heightfield.cpp b/code/Heightfield/Heightfield.cpp
index 3df0ef02f..cbf14c005 100644
--- a/code/Heightfield/Heightfield.cpp
+++ b/code/Heightfield/Heightfield.cpp
@@ -334,30 +334,35 @@ bool Heightfield::queryRay(const Vector4& worldRayOrigin, const Vector4& worldRa
 	{
 		for (int32_t cx = 0; cx < m_size; cx += c_cellSize)
 		{
+			// Calculate bounding box of cell.
 			float cx1w, cz1w;
 			float cx2w, cz2w;
 
 			gridToWorld(float(cx), float(cz), cx1w, cz1w);
 			gridToWorld(float(cx + c_cellSize), float(cz + c_cellSize), cx2w, cz2w);
 
-			const float cyw[] =
-			{
-				unitToWorld(getGridHeightNearest(cx, cz)),
-				unitToWorld(getGridHeightNearest(cx + c_cellSize, cz)),
-				unitToWorld(getGridHeightNearest(cx, cz + c_cellSize)),
-				unitToWorld(getGridHeightNearest(cx + c_cellSize, cz + c_cellSize))
-			};
+			float cy1w = std::numeric_limits< float >::max();
+			float cy2w = -std::numeric_limits< float >::max();
 
-			const float cy1w = *std::min_element(cyw, cyw + sizeof_array(cyw));
-			const float cy2w = *std::max_element(cyw, cyw + sizeof_array(cyw));
+			for (int32_t iz = cz; iz <= cz + c_cellSize; iz += c_skip)
+			{
+				for (int32_t ix = cx; ix <= cx + c_cellSize; ix += c_skip)
+				{
+					const float wy = unitToWorld(getGridHeightNearest(ix, iz));
+					cy1w = std::min(cy1w, wy);
+					cy2w = std::max(cy2w, wy);
+				}
+			}
 
 			Aabb3 bb;
 			bb.mn = Vector4(cx1w, cy1w, cz1w, 1.0f);
 			bb.mx = Vector4(cx2w, cy2w, cz2w, 1.0f);
 
+			// Check if ray intersect bounding box; skip tracing triangles if not.
 			if (!bb.intersectRay(worldRayOrigin, worldRayDirection, kIn, kOut))
 				continue;
 
+			// Construct and trace triangles.
 			for (int32_t iz = cz; iz <= cz + c_cellSize; iz += c_skip)
 			{
 				for (int32_t ix = cx; ix <= cx + c_cellSize; ix += c_skip)
diff --git a/code/Terrain/Editor/TerrainEditModifier.cpp b/code/Terrain/Editor/TerrainEditModifier.cpp
index ad0cd3f41..1e1d191e5 100644
--- a/code/Terrain/Editor/TerrainEditModifier.cpp
+++ b/code/Terrain/Editor/TerrainEditModifier.cpp
@@ -583,27 +583,53 @@ void TerrainEditModifier::apply(
 	if (!m_terrainComponent || m_center.w() <= FUZZY_EPSILON)
 		return;
 
-	// Find furthest intersection which allows for editing around hills etc.
-	Vector4 center = worldRayOrigin;
-	bool found = false;
-	for (;;)
+	Vector4 center = Vector4::zero();
+	Scalar distance;
+
+	if (m_applied)
 	{
-		center += worldRayDirection * 0.01_simd;
+		// Find furthest intersection which allows for editing around hills etc.
+		Scalar minD = Scalar(std::numeric_limits< float >::max());
+		Vector4 step = worldRayOrigin;
+		bool found = false;
+
+		for (;;)
+		{
+			step += worldRayDirection * 0.01_simd;
+
+			if (!m_heightfield->queryRay(
+				step,
+				worldRayDirection,
+				distance
+			))
+				break;
+
+			step = (step + worldRayDirection * distance).xyz1();
+
+			const Scalar d = (step - m_center).xyz0().length();
+			if (d < minD)
+			{
+				center = step;
+				minD = d;
+				found = true;
+			}
+		}
 
-		Scalar distance;
+		if (!found)
+			return;
+	}
+	else
+	{
 		if (!m_heightfield->queryRay(
-			center,
+			worldRayOrigin,
 			worldRayDirection,
 			distance
 		))
-			break;
-
-		center = (center + worldRayDirection * distance).xyz1();
-		found = true;
+			return;
+		
+		center = (worldRayOrigin + worldRayDirection * distance).xyz1();
 	}
-	if (!found)
-		return;
-
+	
 	apply(center);
 }