addition to raylib to create matrix from 3 euler angles (#938)

examples/models/models_yaw_pitch_roll.c

@@ -92,6 +92,7 @@ int main(void)
         while (pitchOffset < -180) pitchOffset += 360;
         pitchOffset *= 10;
 
+        /* matrix transform done with multiplication to combine rotations
         Matrix transform = MatrixIdentity();
 
         transform = MatrixMultiply(transform, MatrixRotateZ(DEG2RAD*roll));
@@ -99,8 +100,11 @@ int main(void)
         transform = MatrixMultiply(transform, MatrixRotateY(DEG2RAD*yaw));
 
         model.transform = transform;
-        //----------------------------------------------------------------------------------
+        */
+        // matrix created from multiple axes at once
+        model.transform = MatrixRotateXYZ((Vector3){DEG2RAD*pitch,DEG2RAD*yaw,DEG2RAD*roll});
 
+        //----------------------------------------------------------------------------------
         // Draw
         //----------------------------------------------------------------------------------
         BeginDrawing();

src/raymath.h

@@ -794,6 +794,33 @@ RMDEF Matrix MatrixRotate(Vector3 axis, float angle)
     return result;
 }
 
+// Returns xyz-rotation matrix (angles in radians)
+RMDEF Matrix MatrixRotateXYZ(Vector3 ang)
+{
+    Matrix result = MatrixIdentity();
+
+    float cosz = cosf(-ang.z);
+    float sinz = sinf(-ang.z);
+    float cosy = cosf(-ang.y);
+    float siny = sinf(-ang.y);
+    float cosx = cosf(-ang.x);
+    float sinx = sinf(-ang.x);
+
+    result.m0 = cosz * cosy;
+    result.m4 = (cosz * siny * sinx) - (sinz * cosx);
+    result.m8 = (cosz * siny * cosx) + (sinz * sinx);
+
+    result.m1 = sinz * cosy;
+    result.m5 = (sinz * siny * sinx) + (cosz * cosx);
+    result.m9 = (sinz * siny * cosx) - (cosz * sinx);
+
+    result.m2 = -siny;
+    result.m6 = cosy * sinx;
+    result.m10= cosy * cosx;
+
+    return result;
+}
+
 // Returns x-rotation matrix (angle in radians)
 RMDEF Matrix MatrixRotateX(float angle)
 {