From ed9cf8800aea07c169719a3efddae7020e6be7e9 Mon Sep 17 00:00:00 2001
From: Eliot Byte <eliotbyte@proton.me>
Date: Thu, 23 Oct 2025 12:29:04 +0300
Subject: [PATCH] fix correct line generation algorithm and bounds calculation
 (#657)

* fix correct line generation algorithm and bounds calculation

- Fix closest_point_on_segment algorithm using proper dot product projection
- Correct loop bounds calculation for radius=0 lines
- Use precise integer arithmetic to avoid rounding errors
- Resolves missing blocks in vertical line structures

* fix ai hallucinations

* polishing closest_point_on_segment

* refactor: extract dot product calculation
---
 src/maths/util.hpp                     | 24 +++++++++++++++++-------
 src/world/generator/WorldGenerator.cpp |  6 +++---
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/maths/util.hpp b/src/maths/util.hpp
index 00345942..2aa3605c 100644
--- a/src/maths/util.hpp
+++ b/src/maths/util.hpp
@@ -118,6 +118,11 @@ namespace util {
         return x * x + y * y + z * z;
     }
 
+    /// @return integer dot product of two vectors
+    inline int dot(const glm::ivec3& a, const glm::ivec3& b) {
+        return a.x * b.x + a.y * b.y + a.z * b.z;
+    }
+
     /// @brief Find nearest point on segment to given
     /// @param a segment point A
     /// @param b segment point B
@@ -144,12 +149,17 @@ namespace util {
     inline glm::ivec3 closest_point_on_segment(
         const glm::ivec3& a, const glm::ivec3& b, const glm::ivec3& point
     ) {
-        auto vec = b - a;
-        float da = distance2(point, a);
-        float db = distance2(point, b);
-        float len = length2(vec);
-        float t = (((da - db) / len) * 0.5f + 0.5f);
-        t = std::min(1.0f, std::max(0.0f, t));
-        return a + glm::ivec3(glm::vec3(vec) * t);
+        glm::ivec3 vec = b - a;
+        int len2 = length2(vec);
+    
+        if (len2 == 0) return a;
+    
+        glm::ivec3 ap = point - a;
+        int dot_product = dot(ap, vec);
+    
+        float t = static_cast<float>(dot_product) / static_cast<float>(len2);
+        t = glm::clamp(t, 0.0f, 1.0f);
+    
+        return a + glm::ivec3(glm::round(glm::vec3(vec) * t));
     }
 }
diff --git a/src/world/generator/WorldGenerator.cpp b/src/world/generator/WorldGenerator.cpp
index e2bf4a86..ccd52db1 100644
--- a/src/world/generator/WorldGenerator.cpp
+++ b/src/world/generator/WorldGenerator.cpp
@@ -547,13 +547,13 @@ void WorldGenerator::generateLine(
     auto b = line.b;
 
     int minX = std::max(0, std::min(a.x-radius-cgx, b.x-radius-cgx));
-    int maxX = std::min(CHUNK_W, std::max(a.x+radius-cgx, b.x+radius-cgx));
+    int maxX = std::min(CHUNK_W, std::max(a.x+radius-cgx, b.x+radius-cgx) + 1);
 
     int minZ = std::max(0, std::min(a.z-radius-cgz, b.z-radius-cgz));
-    int maxZ = std::min(CHUNK_D, std::max(a.z+radius-cgz, b.z+radius-cgz));
+    int maxZ = std::min(CHUNK_D, std::max(a.z+radius-cgz, b.z+radius-cgz) + 1);
 
     int minY = std::max(0, std::min(a.y-radius, b.y-radius));
-    int maxY = std::min(CHUNK_H, std::max(a.y+radius, b.y+radius));
+    int maxY = std::min(CHUNK_H, std::max(a.y+radius, b.y+radius) + 1);
 
     for (int y = minY; y < maxY; y++) {
         for (int z = minZ; z < maxZ; z++) {