Finding point of mesh visible by another game object

Question

In my RTS game i have several enemies shooting at the player character.

Right now i use the characters transform.position as the target for the bullet, but what if the character is partly behind some other object? When enemies shoot at him, the bullet ends on the covering object.

I want the enemies to shoot at some point of the character's mesh that is not covered, still visible by the enemy.

Here is an example image of how i want enemies to act: alt text

Answer 1

There is no straight forward solution for this. There are some simple approximation methods (like casting multiple rays to off-center points inside the target object's bounds) however those aren't reliable. This problem can get infinitly complex as there can be multiple objects limiting the view. So it's possible that only a tiny tiny fraction of the target is visible and it's a nightmare to find that with raycasts and analyzing the occluding geometry to find "holes".

A similar problem is solved with VisPortals, but this requires you to setup those areas and visportals manually.

Another way (if a reliable method is required) is to render the scene into a render texture from the attackers point of view using a replacement shader. This way you can render scene geometry black and enemies white. By analysing the pixel data of the render texture you can determine areas where enemies are visible on a per-pixel basis. This of course shouldn't be done every frame since such a check is quite performance heavy.

In the end you should ask yourself if such a system is worth all the hassle. A lot older games had an AI that did exactly what you've shown in your question as "wrong". Other games simply use "A*" or something similar to find a path to the target and simply move along that path until the target is in range and have a direct line of sight.

Finding point of mesh visible by another game object

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