Hotfix for Vector2LineAngle(), should probably be reviewed along with…

… the rest of raylib angle functions to determine what coordinate system we want. (#3394)

examples/others/raymath_vector_angle.c

@@ -2,15 +2,15 @@
 *
 *   raylib [shapes] example - Vector Angle
 *
-*   Example originally created with raylib 1.0, last time updated with raylib 4.2
+*   Example originally created with raylib 1.0, last time updated with raylib 4.6
 *
 *   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) 2023 Ramon Santamaria (@raysan5)
 *
 ********************************************************************************************/
-
+ 
 #include "raylib.h"
 
 #include "raymath.h"
@@ -28,7 +28,7 @@ int main(void)
     InitWindow(screenWidth, screenHeight, "raylib [math] example - vector angle");
 
     Vector2 v0 = { screenWidth/2, screenHeight/2 };
-    Vector2 v1 = { 100.0f, 80.0f };
+    Vector2 v1 = Vector2Add(v0, (Vector2){ 100.0f, 80.0f });
     Vector2 v2 = { 0 };             // Updated with mouse position
 
     float angle = 0.0f;             // Angle in degrees
@@ -42,21 +42,29 @@ int main(void)
     {
         // Update
         //----------------------------------------------------------------------------------
+        float startangle;
+
+        if (angleMode == 0) startangle = -Vector2LineAngle(v0, v1)*RAD2DEG;
+        if (angleMode == 1) startangle = 0.0f; 
+
+        v2 = GetMousePosition();
+
         if (IsKeyPressed(KEY_SPACE)) angleMode = !angleMode;
 
+        if(angleMode == 0 && IsMouseButtonDown(MOUSE_BUTTON_RIGHT)) v1 = GetMousePosition();
+
         if (angleMode == 0)
         {
             // Calculate angle between two vectors, considering a common origin (v0)
-            v1 = Vector2Add(v0, (Vector2){ 100.0f, 80.0f });
-            v2 = GetMousePosition();
-            angle = Vector2Angle(Vector2Normalize(Vector2Subtract(v1, v0)), Vector2Normalize(Vector2Subtract(v2, v0)))*RAD2DEG;
+            Vector2 v1Normal = Vector2Normalize(Vector2Subtract(v1, v0));
+            Vector2 v2Normal = Vector2Normalize(Vector2Subtract(v2, v0));
+
+            angle = Vector2Angle(v1Normal, v2Normal)*RAD2DEG;
         }
         else if (angleMode == 1)
         {
             // Calculate angle defined by a two vectors line, in reference to horizontal line
-            v1 = (Vector2){ screenWidth/2, screenHeight/2 };
-            v2 = GetMousePosition();
-            angle = Vector2LineAngle(v1, v2)*RAD2DEG;
+            angle = Vector2LineAngle(v0, v2)*RAD2DEG;
         }
         //----------------------------------------------------------------------------------
 
@@ -66,32 +74,40 @@ int main(void)
 
             ClearBackground(RAYWHITE);
 
-            if (angleMode == 0) DrawText("v0", v0.x, v0.y, 10, DARKGRAY);
-            DrawText("v1", v1.x, v1.y, 10, DARKGRAY);
-            DrawText("v2", v2.x, v2.y, 10, DARKGRAY);
-
             if (angleMode == 0)
             {
-                DrawText("MODE: Angle between V1 and V2", 10, 10, 20, BLACK);
+                DrawText("MODE 0: Angle between V1 and V2", 10, 10, 20, BLACK);
+                DrawText("Right Click to Move V2", 10, 30, 20, DARKGRAY);
 
                 DrawLineEx(v0, v1, 2.0f, BLACK);
                 DrawLineEx(v0, v2, 2.0f, RED);
 
-                float startangle = 90 - Vector2LineAngle(v0, v1)*RAD2DEG;
-                DrawCircleSector(v0, 40.0f, startangle, startangle + angle - 360.0f*(angle > 180.0f), 32, Fade(GREEN, 0.6f));
+                DrawCircleSector(v0, 40.0f, startangle, startangle - angle, 32, Fade(GREEN, 0.6f));
             }
             else if (angleMode == 1)
             {
-                DrawText("MODE: Angle formed by line V1 to V2", 10, 10, 20, BLACK);
+                DrawText("MODE 1: Angle formed by line V1 to V2", 10, 10, 20, BLACK);
 
                 DrawLine(0, screenHeight/2, screenWidth, screenHeight/2, LIGHTGRAY);
-                DrawLineEx(v1, v2, 2.0f, RED);
+                DrawLineEx(v0, v2, 2.0f, RED);
 
-                DrawCircleSector(v1, 40.0f, 90.0f, 180 - angle - 90, 32, Fade(GREEN, 0.6f));
+                DrawCircleSector(v0, 40.0f, startangle, startangle - angle, 32, Fade(GREEN, 0.6f));
             }
 
+            DrawText("v0", v0.x, v0.y, 10, DARKGRAY);
+
+            // If the line from v0 to v1 would overlap the text, move it's position up 10
+            if (angleMode == 0 && Vector2Subtract(v0, v1).y > 0.0f) DrawText("v1", v1.x, v1.y-10.0f, 10, DARKGRAY);
+            if (angleMode == 0 && Vector2Subtract(v0, v1).y < 0.0f) DrawText("v1", v1.x, v1.y, 10, DARKGRAY);
+
+            // If angle mode 1, use v1 to emphasize the horizontal line
+            if (angleMode == 1) DrawText("v1", v0.x + 40.0f, v0.y, 10, DARKGRAY);
+
+            // position adjusted by -10 so it isn't hidden by cursor
+            DrawText("v2", v2.x-10.0f, v2.y-10.0f, 10, DARKGRAY);
+
             DrawText("Press SPACE to change MODE", 460, 10, 20, DARKGRAY);
-            DrawText(TextFormat("ANGLE: %2.2f", angle), 10, 40, 20, LIME);
+            DrawText(TextFormat("ANGLE: %2.2f", angle), 10, 70, 20, LIME);
 
         EndDrawing();
         //----------------------------------------------------------------------------------

src/raymath.h

@@ -323,6 +323,8 @@ RMAPI float Vector2Angle(Vector2 v1, Vector2 v2)
 
     float dot = v1.x*v2.x + v1.y*v2.y;
     float det = v1.x*v2.y - v1.y*v2.x;
+
+    // TODO(10/9/2023): Currently angles move clockwise, determine if this is wanted behavior
     result = -atan2f(det, dot);
 
     return result;
@@ -335,7 +337,8 @@ RMAPI float Vector2LineAngle(Vector2 start, Vector2 end)
 {
     float result = 0.0f;
 
-    result = atan2f(end.y - start.y, end.x - start.x);
+    // TODO(10/9/2023): Currently angles move clockwise, determine if this is wanted behavior
+    result = -atan2f(end.y - start.y, end.x - start.x);
 
     return result;
 }