Rotate Sprite

[prondzyk]

Hi my first post
I was writning code which rotate sprite and follows the cursor.

Code: [Select]


Sprite.SetCenter(Sprite.GetSize() / 2.f);
if (App.GetInput().GetMouseX() <= Sprite.GetPosition().x) {
   Sprite.SetRotation  (-1 * 360/ 3.1415926535 * (atan(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) / static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))));
      } else {
      Sprite.SetRotation  (-1 * 360/ 3.1415926535 *(atan(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) /      static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))));
      }

but it doesn't work properly. Sprite (its rifle)isn't parallel to cursor.
It look like that:


What is wrong?

[Laurent]

First, use atan2 rather than atan. The former gives the unique angle corresponding to the cos/sin pair, while the latter will give the same result for opposite angles (cos/sin == -cos/-sin).

Then, you should use App.ConvertCoords to map mouse coordinates to "scene" coordinates. It may not be important if you use the default view, but it's cleaner and will avoid stupid errors if you use views later

[prondzyk]

Now I have:

Code: [Select]


Sprite.SetCenter(Sprite.GetSize() / 2.f);
if (App.GetInput().GetMouseX() <= Sprite.GetPosition().x) {
   Sprite.SetRotation  (-1* 360 / 3.1415926535 * (atan2(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) , static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))));
      } else {
      Sprite.SetRotation  (-1* 360 / 3.1415926535 *(atan2(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) ,      static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))));
      }
App.ConvertCoords(App.GetInput().GetMouseX(), App.GetInput().GetMouseY());
but still doesn't work properly. The same story :/

EDIT:
Success! It must look like this:

Code: [Select]

Sprite.SetCenter(Sprite.GetSize() / 2.f);
if (App.GetInput().GetMouseX() <= Sprite.GetPosition().x) {
   Sprite.SetRotation  (((-1* 360 / 3.1415926535 * (atan2(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) , static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))))/2)+90);
      } else {
      Sprite.SetRotation  (((-1* 360 / 3.1415926535 *(atan2(   static_cast<double> (Sprite.GetPosition().y - App.GetInput().GetMouseY()) ,      static_cast<double> (Sprite.GetPosition().x - App.GetInput().GetMouseX()))))/2)+90);
      }
Thanks for help!