Rotate a point in 3D space with sine and cosine

I got my camera controlled by the mouse. Now I want a sphere to be always in the center of my view(just for testing). I tried that by assigning the sine of the Y rotation of the camera times 10 as the X coordinate and the same for the Y coordinate but with cosine:

SphereX = 10 * math.sin(YRotation)
SphereY = 10 * math.cos(YRotation)


But now I would like to know how to set the Z position. I can set the proper height of the sphere by doing that:

SphereZ = 10 * math.sin(XRotation)


But the problem is, that the sphere is only moving up and down and the moving towards the camera is ignored. How can I fix that?

• You want the sphere to be in front of the camera, at a constant distance no matter where you move the camera? Or you want to do something like orbiting the sphere and being able to zoom in and out on it? – MichaelHouse Aug 8 '13 at 23:01
• The first one. :D – Liess Jemai Aug 8 '13 at 23:03
• Are you set on using sine and cosine? Might be easier with matrices: gamedev.stackexchange.com/questions/11594 – MichaelHouse Aug 8 '13 at 23:20
• Actually I just want the direction the camera is looking at. I wanted to solve that by calculating a kind of a target. – Liess Jemai Aug 8 '13 at 23:26
• Got it working. The camera direction is the negative of the third row of the viewing matrix. – Liess Jemai Aug 8 '13 at 23:58