From 19dfd78d4269d56bd34ab72f6b701be9f84b9719 Mon Sep 17 00:00:00 2001
From: Daniel Karbach <daniel.karbach@localhorst.tv>
Date: Fri, 26 Jun 2015 15:10:10 +0200
Subject: [PATCH] better edge light propagation on link

---
 TODO                |  2 ++
 src/world/chunk.cpp | 68 +++++++++++++++++++++------------------------
 2 files changed, 34 insertions(+), 36 deletions(-)

diff --git a/TODO b/TODO
index a0c8c1d..4025ad5 100644
--- a/TODO
+++ b/TODO
@@ -50,6 +50,8 @@ entity ai
 
 	there's a bug where a chunk's model is not updated if its neighbor
 	changes border light levels
+	I kinda mitigated it a little for direct neighbors during linking, but
+	it still can happen in (hopefully) rare corner cases
 
 gravity
 
diff --git a/src/world/chunk.cpp b/src/world/chunk.cpp
index a65f5c3..75f9c4f 100644
--- a/src/world/chunk.cpp
+++ b/src/world/chunk.cpp
@@ -186,6 +186,26 @@ void Chunk::SetBlock(int index, const Block &block) noexcept {
 	}
 }
 
+namespace {
+
+// propagate light from a's edge to b
+void edge_light(
+	Chunk &a, const Chunk::Pos &a_pos,
+	Chunk &b, const Chunk::Pos &b_pos
+) noexcept {
+	if (a.GetLight(a_pos) > 1) {
+		const BlockType &b_type = b.Type(Chunk::ToIndex(b_pos));
+		if (!b_type.block_light) {
+			light_queue.emplace(&a, a_pos);
+		}
+		if (b_type.visible) {
+			b.Invalidate();
+		}
+	}
+}
+
+}
+
 void Chunk::SetNeighbor(Chunk &other) noexcept {
 	if (other.position == position + Pos(-1, 0, 0)) {
 		if (neighbor[Block::FACE_LEFT] != &other) {
@@ -195,12 +215,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int y = 0; y < height; ++y) {
 					Pos my_pos(0, y, z);
 					Pos other_pos(width - 1, y, z);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
@@ -213,12 +229,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int y = 0; y < height; ++y) {
 					Pos my_pos(width - 1, y, z);
 					Pos other_pos(0, y, z);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
@@ -231,12 +243,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int x = 0; x < width; ++x) {
 					Pos my_pos(x, 0, z);
 					Pos other_pos(x, height - 1, z);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
@@ -249,12 +257,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int x = 0; x < width; ++x) {
 					Pos my_pos(x, height - 1, z);
 					Pos other_pos(x, 0, z);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
@@ -267,12 +271,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int x = 0; x < width; ++x) {
 					Pos my_pos(x, y, 0);
 					Pos other_pos(x, y, depth - 1);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
@@ -285,12 +285,8 @@ void Chunk::SetNeighbor(Chunk &other) noexcept {
 				for (int x = 0; x < width; ++x) {
 					Pos my_pos(x, y, depth - 1);
 					Pos other_pos(x, y, 0);
-					if (GetLight(my_pos) > 0) {
-						light_queue.emplace(this, my_pos);
-					}
-					if (other.GetLight(other_pos) > 0) {
-						light_queue.emplace(&other, other_pos);
-					}
+					edge_light(*this, my_pos, other, other_pos);
+					edge_light(other, other_pos, *this, my_pos);
 				}
 			}
 			work_light();
-- 
2.39.2