From 5120d97be542480ff44ca0a236c3fa15eaac6e78 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Mon, 7 Nov 2011 15:37:00 +0000
Subject: [PATCH] tutorial: continuous color in the Mandelbrot viewer.

---
 test/tutorial/tut03.cpp | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/test/tutorial/tut03.cpp b/test/tutorial/tut03.cpp
index 59b08192..7ccb2c86 100644
--- a/test/tutorial/tut03.cpp
+++ b/test/tutorial/tut03.cpp
@@ -27,6 +27,7 @@ using namespace lol;
 
 #if defined _WIN32
 #   undef main /* FIXME: still needed? */
+#   include <direct.h>
 #endif
 
 class Fractal : public WorldEntity
@@ -114,18 +115,40 @@ public:
             /* FIXME: this object never cleans up */
         }
 
-        m_angle += deltams * 0.001f;
+        m_angle += deltams * 0.0001f;
 
-        cmplx r0(cosf(m_angle), 0.3f * sinf(m_angle));
+        cmplx r0(cosf(m_angle), 0.5f * sinf(m_angle));
         for (int j = 0; j < m_size.y; j++)
         for (int i = 0; i < m_size.x; i++)
         {
             cmplx x0(4.0f / m_size.x * i - 2.5f, 3.0f / m_size.y * j - 1.5f);
             cmplx r = x0 * r0;
+            cmplx z;
             int iter = 20;
-            for (cmplx z = r; iter && z.sqlen() < 4.0f; z = z * z + r)
+            for (z = r; iter && z.sqlen() < 4.0f; z = z * z + r)
                 --iter;
-            m_pixels[j * m_size.x + i] = u8vec4(0, iter * 12, iter * 12, 0);
+
+            float f = iter;
+            float n = z.sqlen();
+            if (n > 36.0f)
+                f += 2.0f;
+            if (n > 16.0f)
+                f += 1.0f + (n - 16.0f) / 20.0f;
+            else if (n > 4.0f)
+                f += (n - 4.0f) / 12.0f;
+
+            if (iter)
+            {
+                uint8_t red = 255 - f * 11;
+                uint8_t green = 255 - f * 11;
+                uint8_t blue = (f * 23 > 255) ? 511 - f * 23 : 255;
+                //uint8_t blue = f * 36 < 255 ? f * 36 : 255;
+                m_pixels[j * m_size.x + i] = u8vec4(red, green, blue, 0);
+            }
+            else
+            {
+                m_pixels[j * m_size.x + i] = u8vec4(0, 0, 0, 0);
+            }
         }
 
         glEnable(GL_TEXTURE_2D);
@@ -185,6 +208,10 @@ private:
 
 int main()
 {
+#if defined _WIN32
+    _chdir("../..");
+#endif
+
     Application app("Tutorial 3: Fractal", ivec2(640, 480), 60.0f);
 
     new DebugFps(5, 5);