Question

I use Sprites to draw images in a D3D window. I draw an image on every sprite within a rectangle (0, 0, width, height) and use Matrix.Transformation2D to place the image in the rendered view.

Example:

using (Sprite s = new Sprite(device))
   {
      s.Begin(SpriteFlags.AlphaBlend);
      Matrix tranz = new Matrix();
      tranz =
         Matrix.Transformation2D(new Vector2(0, 0), 0.0f,
            new Vector2(scale, scale),
            new Vector2(0, 0), Geometry.DegreeToRadian(angle),
            new Vector2(positionX, positionY));

      s.Transform = tranz;

      Vector3 spriteCenter = new Vector3(0.0f, 0.0f, 0.0f);
      Vector3 sprPosition = new Vector3(0.0f, 0.0f, 0.0f);

      s.Draw(someTexture, new Rectangle(0, 0, width, height), 
         spriteCenter, sprPosition,
         Color.FromArgb(0xff, 255, 255, 255));
      s.End();
   }

How can I detect that a certain image was clicked?

Known parameters:
1. Mouse position: mouseX, mouseY
2. All transformation2D parameters
3. Size and position of the image within a sprite.

This should be enough data to get what I want, but I have no clue what to do.

BTW – no world transformation nor other to include in the calculation. I Just transform the sprites.

Answer 1

You should be able to do it using matrix.Invert(). Pseudocode:

Foreach sprite
    Matrix inverse = tranz.Invert()
    objectCoords = mouseCoords * inverse;
    if (objectCoords in (0,0,width, height))
        return sprite

return null;