Add hilbert curve example (#5454)

examples/shapes/shapes_hilbert_curve.c

@@ -0,0 +1,187 @@
+/*******************************************************************************************
+*
+*   raylib [shapes] example - hilbert curve example
+*
+*   Example complexity rating: [★★★☆] 3/4
+*
+*   Example originally created with raylib 5.6, last time updated with raylib 5.6
+*
+*   Example contributed by Hamza RAHAL (@hmz-rhl)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2025 Hamza RAHAL (@hmz-rhl)
+*
+********************************************************************************************/
+
+
+#include "raylib.h"
+#include "raymath.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+const int screenWidth = 800;
+
+const int screenHeight = 450;
+
+int order = 2;
+
+int total;
+
+int counter = 0;
+
+Vector2 *hilbertPath = 0;
+
+const Vector2 hilbertPoints[4] =
+{
+    [0] = {
+        .x = 0,
+        .y = 0
+    },
+    [1] = {
+        .x = 0,
+        .y = 1
+    },
+    [2] = {
+        .x = 1,
+        .y = 1
+    },
+    [3] = {
+        .x = 1,
+        .y = 0
+    },
+};
+
+//------------------------------------------------------------------------------------
+// Module Functions Declaration
+//------------------------------------------------------------------------------------
+Vector2 Hilbert(int index);
+
+void InitHilbertPath(void);
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - hilbert curve example");
+
+    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
+
+    InitHilbertPath();
+    
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    //--------------------------------------------------------------------------------------
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        if ((IsKeyPressed(KEY_UP)) && (order < 8))
+        {
+            counter = 0;
+            ++order;
+            InitHilbertPath();
+        }
+        else if((IsKeyPressed(KEY_DOWN)) && (order > 1))
+        {
+            counter = 0;
+            --order;
+            InitHilbertPath();
+        }
+        //----------------------------------------------------------------------------------
+        
+        // Draw
+        //--------------------------------------------------------------------------
+        BeginDrawing();
+        DrawText(TextFormat("(press UP or DOWN to change)\norder : %d", order), screenWidth/2 + 70, 25, 20, WHITE);
+        
+        if(counter < total)
+        {
+            ClearBackground(BLACK);
+            for (int i = 1; i <= counter; i++)
+            {
+                DrawLineV(hilbertPath[i], hilbertPath[i-1], ColorFromHSV(((float)i / total) * 360.0f, 1.0f, 1.0f));
+            }
+            counter += 1;
+        }
+        EndDrawing();
+        //--------------------------------------------------------------------------
+    }
+    //--------------------------------------------------------------------------------------
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    MemFree(hilbertPath);
+    //--------------------------------------------------------------------------------------
+    return 0;
+}
+
+//------------------------------------------------------------------------------------
+// Module Functions Definition
+//------------------------------------------------------------------------------------
+
+// calculate U positions
+Vector2 Hilbert(int index)
+{
+
+    int hiblertIndex = index&3;
+    Vector2 vect = hilbertPoints[hiblertIndex];
+    float temp;
+    int len;
+
+    for (int j = 1; j < order; j++)
+    {
+        index = index>>2;
+        hiblertIndex = index&3;
+        len = 1<<j;
+        switch (hiblertIndex)
+        {
+            case 0:
+                temp = vect.x;
+                vect.x = vect.y;
+                vect.y = temp;
+                break;
+            case 2:
+                vect.x += len;
+            case 1:
+                vect.y += len;
+                break;
+            case 3:
+                temp = len - 1 - vect.x;
+                vect.x = 2*len - 1 - vect.y;
+                vect.y = temp;
+                break;
+        }
+    }
+    return vect;
+}
+
+// Calculate the whole Hilbert Path (including each U and their link)
+void InitHilbertPath(void)
+{
+    int N;
+    float len;
+    N = 1<<order;
+    total = N*N;
+    MemFree(hilbertPath);
+    hilbertPath = NULL;
+    hilbertPath = (Vector2*)MemAlloc(sizeof(Vector2)*total);
+    if(hilbertPath == NULL)
+    {
+        printf("%s: malloc failed\n", __func__);
+    }
+    len = (float)screenHeight/N;
+    for (int i = 0; i < total; i++)
+    {
+        hilbertPath[i] = Hilbert(i);
+        hilbertPath[i].x = hilbertPath[i].x*len + len/2.0f;
+        hilbertPath[i].y = hilbertPath[i].y*len + len/2.0f;
+    }
+}