add drawing rotation shape example

examples/Makefile

@@ -536,7 +536,8 @@ SHAPES = \
     shapes/shapes_rectangle_scaling \
     shapes/shapes_splines_drawing \
     shapes/shapes_top_down_lights \
-    shapes/shapes_rectangle_advanced
+    shapes/shapes_rectangle_advanced \
+    shapes/shapes_custom_rotation
 
 TEXTURES = \
     textures/textures_background_scrolling \

examples/shapes/shapes_custom_rotation.c

@@ -0,0 +1,187 @@
+/*******************************************************************************************
+ *
+ *   raylib [shapes] example - draw rotation shapes
+ *
+ *   Example originally created with raylib 5.5
+ *
+ *   Example contributed by Vlad Adrian (@demizdor) and reviewed by Ramon Santamaria (@raysan5)
+ *
+ *   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) 2022-2024 Lu Hong (@CManLH)
+ *
+ ********************************************************************************************/
+#include <math.h>
+
+#include "raylib.h"
+#include "rlgl.h"
+
+// Fetch new coordinates of a point after it rotates around a center point by a certain angle
+Vector2 RotatePointAroundPoint(Vector2 point, Vector2 center, float angle);
+
+// Draw ellipse with rotation
+void DrawEllipseRotation(Vector2 center, float radiusH, float radiusV, Color color, float angle);
+
+// Draw ellipse outline with rotation
+void DrawEllipseLinesRotation(Vector2 center, float radiusH, float radiusV, Color color, float angle);
+
+// Draw rectangle with rotation
+void DrawRectangleRotation(Vector2 point, float width, float height, Color color, float angle);
+
+// Draw rectangle outline with rotation
+void DrawRectangleLinesRotation(Vector2 point, float width, float height, Color color, float angle);
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 1024;
+    const int screenHeight = 480;
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - draw rotation shapes");
+
+    float angle = PI / 6.0f;
+
+    float ellipseRadiusH = 32.0f;
+    float ellipseRadiusV = 72.0f;
+
+    float rectangleWidth = 64.0f;
+    float rectangleHeight = 128.0f;
+
+    SetTargetFPS(60); // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose()) // Detect window close button or ESC key
+    {
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+        ClearBackground(RAYWHITE);
+
+        // Draw rectangle
+        DrawRectangleRotation((Vector2){128, 20}, rectangleWidth, rectangleHeight, SKYBLUE, angle);
+        DrawText("Rotation Rectangle", 64, 84, 20, BLACK);
+
+        // Draw rectangle outline
+        DrawRectangleLinesRotation((Vector2){128, 256}, rectangleWidth, rectangleHeight, DARKGREEN, angle);
+        DrawText("Rotation Rectangle Outline", 16, 320, 20, BLACK);
+
+        // Draw ellipse with rotation
+        DrawEllipseRotation((Vector2){432, 84}, ellipseRadiusH, ellipseRadiusV, SKYBLUE, angle);
+        DrawText("Rotation Ellipse", 336, 84, 20, BLACK);
+
+        // Draw ellipse outline with rotation
+        DrawEllipseLinesRotation((Vector2){432, 320}, ellipseRadiusH, ellipseRadiusV, DARKGREEN, angle);
+        DrawText("Rotation Ellipse outline", 320, 320, 20, BLACK);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    CloseWindow(); // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}
+
+void DrawEllipseRotation(Vector2 center, float radiusH, float radiusV, Color color, float angle)
+{
+    rlBegin(RL_TRIANGLES);
+        rlColor4ub(color.r, color.g, color.b, color.a);
+        Vector2 startPoint = RotatePointAroundPoint((Vector2){center.x + radiusH, center.y}, center, angle);
+        for (int i = 0; i < 360; i += 10)
+        {
+            Vector2 endPoint = RotatePointAroundPoint((Vector2){center.x + cosf(DEG2RAD * (i + 10)) * radiusH, center.y + sinf(DEG2RAD * (i + 10)) * radiusV}, center, angle);
+            rlVertex2f(center.x, center.y);
+            rlVertex2f(endPoint.x, endPoint.y);
+            rlVertex2f(startPoint.x, startPoint.y);
+
+            startPoint = endPoint;
+        }
+    rlEnd();
+}
+
+void DrawEllipseLinesRotation(Vector2 center, float radiusH, float radiusV, Color color, float angle)
+{
+    rlBegin(RL_LINES);
+        rlColor4ub(color.r, color.g, color.b, color.a);
+        Vector2 startPoint = RotatePointAroundPoint((Vector2){center.x + radiusH, center.y}, center, angle);
+        for (int i = 0; i < 360; i += 10)
+        {
+            Vector2 endPoint = RotatePointAroundPoint((Vector2){center.x + cosf(DEG2RAD * (i + 10)) * radiusH, center.y + sinf(DEG2RAD * (i + 10)) * radiusV}, center, angle);
+            rlVertex2f(startPoint.x, startPoint.y);
+            rlVertex2f(endPoint.x, endPoint.y);
+
+            startPoint = endPoint;
+        }
+    rlEnd();
+}
+
+void DrawRectangleRotation(Vector2 point, float width, float height, Color color, float angle)
+{
+    rlBegin(RL_TRIANGLES);
+        rlColor4ub(color.r, color.g, color.b, color.a);
+
+        Vector2 center = (Vector2){point.x + width / 2.0f, point.y + height / 2.0f};
+        Vector2 newTopLeft = RotatePointAroundPoint(point, center, angle);
+        Vector2 newTopRight = RotatePointAroundPoint((Vector2){point.x + width, point.y}, center, angle);
+        Vector2 newBottomLeft = RotatePointAroundPoint((Vector2){point.x, point.y + height}, center, angle);
+        Vector2 newBottomRight = RotatePointAroundPoint((Vector2){point.x + width, point.y + height}, center, angle);
+
+        rlVertex2f(newTopLeft.x, newTopLeft.y);
+        rlVertex2f(newBottomLeft.x, newBottomLeft.y);
+        rlVertex2f(newTopRight.x, newTopRight.y);
+
+        rlVertex2f(newTopRight.x, newTopRight.y);
+        rlVertex2f(newBottomLeft.x, newBottomLeft.y);
+        rlVertex2f(newBottomRight.x, newBottomRight.y);
+    rlEnd();
+}
+
+void DrawRectangleLinesRotation(Vector2 point, float width, float height, Color color, float angle)
+{
+    rlBegin(RL_LINES);
+        rlColor4ub(color.r, color.g, color.b, color.a);
+
+        Vector2 center = (Vector2){point.x + width / 2.0f, point.y + height / 2.0f};
+        Vector2 newLeftTop = RotatePointAroundPoint(point, center, angle);
+        Vector2 newRightTop = RotatePointAroundPoint((Vector2){point.x + width, point.y}, center, angle);
+        Vector2 newLeftBottom = RotatePointAroundPoint((Vector2){point.x, point.y + height}, center, angle);
+        Vector2 newRightBottom = RotatePointAroundPoint((Vector2){point.x + width, point.y + height}, center, angle);
+
+        rlVertex2f(newLeftTop.x, newLeftTop.y);
+        rlVertex2f(newRightTop.x, newRightTop.y);
+
+        rlVertex2f(newRightTop.x, newRightTop.y);
+        rlVertex2f(newRightBottom.x, newRightBottom.y);
+
+        rlVertex2f(newRightBottom.x, newRightBottom.y);
+        rlVertex2f(newLeftBottom.x, newLeftBottom.y);
+
+        rlVertex2f(newLeftBottom.x, newLeftBottom.y);
+        rlVertex2f(newLeftTop.x, newLeftTop.y);
+    rlEnd();
+}
+
+Vector2 RotatePointAroundPoint(Vector2 point, Vector2 center, float angle)
+{
+    // Vector center->point
+    float x = point.x - center.x;
+    float y = point.y - center.y;
+
+    // new vector after rotation
+    float cosres = cosf(angle);
+    float sinres = sinf(angle);
+    float newX = x * cosres - y * sinres;
+    float newY = x * sinres + y * cosres;
+
+    // new point
+    return (Vector2){newX + center.x, newY + center.y};
+}