From 5e6633783b14cd23f30811ad0dd5e1cb4632779f Mon Sep 17 00:00:00 2001
From: Linghui Zeng <lh.zeng@hotmail.com>
Date: Mon, 7 Oct 2024 14:47:44 +0800
Subject: [PATCH] Simple speed up of Lesson 1
 https://github.com/ssloy/tinyrenderer/issues/28

---
 main.cpp | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/main.cpp b/main.cpp
index 110ef2e..792a8dc 100644
--- a/main.cpp
+++ b/main.cpp
@@ -22,21 +22,31 @@ void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color)
     int derror2 = std::abs(dy) * 2;
     int error2 = 0;
     int y = y0;
-    for (int x=x0; x <= x1; x++)
+    const int yinc = (y1 > y0? 1 : -1);
+    if (steep)
     {
-        if (steep)
+        for (int x=x0; x <= x1; x++)
         {
             image.set(y, x, color);
+            error2 += derror2;
+            if (error2 > dx)
+            {
+                y += yinc;
+                error2 -= dx * 2;
+            }
         }
-        else
+    }
+    else
+    {
+        for (int x=x0; x <= x1; x++)
         {
             image.set(x, y, color);
-        }
-        error2 += derror2;
-        if (error2 > dx)
-        {
-            y += (y1 > y0? 1 : -1);
-            error2 -= dx * 2;
+            error2 += derror2;
+            if (error2 > dx)
+            {
+                y += yinc;
+                error2 -= dx * 2;
+            }
         }
     }
 }