Turn transparent when behind wall, how to do this ?

This might sounds newbie description, but I don't know if this is just the shader thing.

Ok, I have an player and a wall, when the player is in front of the wall, it's just regular shading. And when the player goes behind the wall, the ghost shape of the player is projected on the wall. I saw this effect in couple of games, the latest one is Torchlight.

Just curious if anybody knows how this can be achieved by shader. thanks.

Fang

 

hi Daniel,

thank you very much. Another newbie question, is this supposed to be applied to the wall, right ? And how do I make the switch from show-through to no show-through? I actually just start to read the shaderlib manual.

Fang

 

oh, man, this sounds exactly I wanted, I'll test it tonight. thanks you very much Daniel, you made the task trivial now

 

Thanks Daniel, I just tested, it works perfect, when the object under shader is behind something, it's plotted using a blue color. Awesome. I'm sure this shader can turn into other kool stuff as well.

 

Daniel, that's really cool. Thanks for giving me ideas!

Do you have any method to turn objects transparent only when certain meshes go behind them? (e.g. the player character)? I really like this effect in games. Seems like a much more complicated situation, but I've seen it a lot, so perhaps there is a common solution?

 

I figured that was how it needed to be done. But I hadn't thought of what you posted in this thread, so I didn't know if there was some shader trick I didn't know about, to "automate" this.

 

I'm new to unity and trying to use this code but I keep getting and error on the first lane saying 'Shader' unexpected symbol. Any tips on how to fix this? or am I just creating the shader wrong?

 

Hi @rylmtn ,

I think you made a little mistake. You created a " C# " script and not a " shader => standard surface shader " to paste this code.

 

I'm trying to use this shader for an object lit by light probes and the model appears black. Does anyone know how to integrate light probe info into this?

 

good solution but i want to make show only outline without filling

 

Hello guys, I've created a complete tutorial to achieve the desired effect:
https://gamedevelopertips.com/how-can-i-create-a-see-behind-walls-effect-in-unity/
I hope it's helpful.

 

I want to turn the Lighting off to have it be fullbright but when i do that it is not coloured anymore

 

If you want to use the shader on 2nd reply for many (semi-) transparent models in the same scene (eg a party of characters going behind a wall at the same time) keep in mind that you are going to run into drawing order problems, since the render queue used is opaque and Unity sorts front-to-back by default in these queues.

For correct transparency, apart from a suitable blend mode, you also need to use a back-to-front sorting render queue (eg Transparent). But if you try to do this with a separate transparent material, the triangles on the back of your model will mess everything up since they will always render because they will pass the "ZTest Greater" depth test (they are occluded by the geometry of the same mesh in front of them).

A solution to this situation is to use stencils: have a stencil-only pre-pass in your opaque shader and "flag" the pixels that will need to be transparent:

Code (CSharp):

1.  Pass {
2.          
3.             ZWrite Off        //we MUST NOT write to depth buffer (else below passes will also render)!
4.             ZTest Greater    //depth test will succeed when geometry is occluded
5.             ColorMask 0        //do not write anything on screen!
6.  
7.             Stencil
8.             {
9.                 Ref 1            //value that will be written to stencil buffer
10.                 Comp Always        //stencil test will always succeed
11.                 Pass Replace    //if depth test succeeds write ref value
12.             }
13.         }

When your transparent material renders later on, perform a stencil test against the same reference value:

Code (CSharp):

1.  Pass
2.         {
3.             ZTest Greater                   //we still need this as depth test will always happen after stencil test
4.             ZWrite Off                      //do not write anything to z-buffer (else geometry behind ours won't render)
5.             Blend SrcAlpha OneMinusSrcAlpha //classic transparency blend mode
6.  
7.             Stencil
8.             {
9.                 Ref 1      
10.                 Comp Equal  //if stencil buffer for this pixel equals our flag value then stencil test succeeds
11.                 Pass Keep   //do not do anything if depth + stencil tests succeeds (stencil buffer will be cleared anyway next frame)
12.             }
13.             CGPROGRAM
14.             //your shader here
15.             ENDCG
16.         }
17.