How to implement aimspot on billiard ball

Questions & Answers
1

Hi,

I have a white ball. When I press right mouse button blue spot should appear on the ball(aimspot). It should be possible to move this spot.
What is the simplest solution in Unity? Additional texture with uv shifting?

2

A simple solution might be to attach a Projector to the tip of the cue stick, that projects a texture with a blue circle in it. The projector will take care of texturemapping the circle texture onto whatever geometry it hits. This is really easy to set up, but has a few added side-effects that you’ll want to take care of:

  1. Firstly, it’ll project the aim spot onto
    other balls behind the cue ball if
    they happen to be in its line of
    sight, and that’s definitely not
    what you want. You can fix that by
    adding the cue ball to a layer of
    its own, and then add everything BUT
    that layer to the Projector’s
    IgnoreLayers. That way, it’ll only
    project on the cue ball.
  2. Secondly, it will change the size of
    the aimspot based on the cue tip’s
    distance to the cue ball. That will
    give you a larger spot when the cue
    tip is far away and a small one
    close up, which may or may not be
    okay, that’s up to you. If you want
    it to remain constant, you can
    change the Projector’s field of view
    as a function of distance so that it
    becomes small when far away and
    wider when close up.

There is also a way that doesn’t involve a Projector. You can do a Physics.Raycast from the cue stick’s tip and forward. It returns a RaycastHit-object, that gives you a lot of useful information about the geometry it hit (the cue ball). See:

http://unity3d.com/support/documentation/ScriptReference/RaycastHit.html

Perhaps you can use the UV coordinates or the point the ray hit to position the aim spot texture.