raycast with transparent shader

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Hello there unity community! This will be my first question and I fear it is one without a good answer.

I'm creating a game with a slightly isometric perspective, but featuring 3d objects with interiors. You issue orders to your soldiers by clicking the map, they create a path and head towards it (using navmesh and agents)

Now I have this problem.. you need to be able to issue orders to move inside the buildings, between floords.. but.. there are roofs.

So to tackle this is I wrote a cutaway shader that I can control. This works beautifully. However it presents another problem. To actually tell the agents where in 3d space to move, i raycast from the camera and get a position of first collision. However, because this transparency is being created in a shader, this raycast still sees the object as if it has a roof (which makes sense..)

My question to the brilliant minds of the unity community:

Is there an elegant solution for dealing with raycasting through transparent objects?

alt text

I come from a visual effects background so.. i've got some ideas of generating a world position pass, then figuring out the pixel color under the mouse, then using this to generate the actual location in 3d space.. somehow all offscreen..

but i know this issue has come up before in game development. I think about all the times that i've fired a rife through a fence (that is made with a transparent texture) when the texture is present, the bullet collides with the fence, when firing through the gaps, it strikes the character behind. How are they doing this?

Answer 1

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Answer by whydoidoit · Oct 21, 2013 at 08:06 PM

So try this:

Flag the floor/ceiling objects with a tag of "Floor"
Use RaycastAll to get a list of all of the hits

Work through that list ignoring floor tagged objects that are above your cutaway position and take the first non-cutaway object as being your hit.

  using System.Linq;
     ...
     bool Cast(Vector3 position, Vector3 direction, float distance, out RaycastHit result, LayerMask mask, float cutOffPoint)
     {
     
        var hits = Physics.RaycastAll(position, direction, distance, mask).OrderBy(h=>h.distance);
        foreach(var hit in hits)
        {
            if(!hit.collider.CompareTag("Floor") || hit.point.y < cutOffPoint)
            {
                  result = hit;
                  return true;
            }
        }
        return false;
     
     }

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mradfo21 · Oct 21, 2013 at 08:09 PM 0

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thats a very good idea!

whydoidoit · Oct 22, 2013 at 10:44 AM 0

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If it works for you, could you tick the answer?

raycast with transparent shader

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