Question How to mask out part of a 3D object outside of boundaries of another 3D object

Hi,

I have a 3D Object imitating an archery target. I also have a few 3D objects (planes) that imitate marks where shots hit the target. At present, the mark objects are drawn fully including the areas that go outside of the boundaries of the target. Is it possible to mask out these mark areas to show only what is within the target? The image shows what it is now and what I am trying to achieve.

I have made some research and looks like the way to do it would be through writing some code in the shader (I am using URP). However, it is not clear what exactly should I do. Your help would be greatly appreciated!

Thanks,

IT

 

So, I dug a little bit deeper, and applied a stencil shader like the following. I created a Sprite (circle) located right in front of the target and used this shader for it:

Code (CSharp):

1.  
2. Shader "Custom/StencilMask" {
3.  
4.     Properties {
5.             _Color ("Color", Color) = (1,1,1,1)
6.             _StencilMask("Stencil Mask", Range(0, 255)) = 1
7.         }
8.         SubShader {
9.             Tags { "RenderType"="Transparent" "Queue"="Geometry-1"}
10.             LOD 200
11.  
12.             //ColorMask 0
13.             Stencil {
14.                 Ref 1
15.                 Comp Never
16.                 Fail Replace
17.             }
18.             Pass{}
19.         }
20.  
21. }
22.  

For the Mark, I used the following shader:

Code (CSharp):

1.  
2. Shader "Custom/StencilEffect" {
3.     Properties {
4.         _MainTex ("Base (RGB)", 2D) = "white" {}
5.     }
6.     SubShader {
7.         Tags { "RenderType"="Opaque"}
8.  
9.         Stencil {
10.             Ref 1
11.             Comp equal
12.             Pass Keep
13.         }
14.  
15.         CGPROGRAM
16.         #pragma surface surf Lambert
17.  
18.         sampler2D _MainTex;
19.  
20.         struct Input {
21.             float2 uv_MainTex;
22.         };
23.  
24.         void surf (Input IN, inout SurfaceOutput o) {
25.             half4 c = tex2D (_MainTex, IN.uv_MainTex);
26.             o.Albedo = c.rgb;
27.             o.Alpha = c.a;
28.         }
29.         ENDCG
30.     }
31.     FallBack "Diffuse"
32. }
33.  

So, two issues now. I do not see the marks only if I look at them from the back side of the target (not from the camera view) as shown in the images. Second issue: my Marks are pink rectangles now, a texture with a circle is gone. Anyway to apply it using a custom shader?

Thanks a lot!

IT

 

So, I have almost solved the issue.

First, I created a transparent sprite circle and put it on top of the target. Used the following shader:

Code (CSharp):

1.  
2. Shader "Custom/StencilMaskShader"
3. {
4.     Properties
5.     {
6.         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
7.         _Color ("Tint", Color) = (1,1,1,1)
8.         [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
9.         [HideInInspector] _RendererColor ("RendererColor", Color) = (1,1,1,1)
10.         [HideInInspector] _Flip ("Flip", Vector) = (1,1,1,1)
11.         [PerRendererData] _AlphaTex ("External Alpha", 2D) = "white" {}
12.         [PerRendererData] _EnableExternalAlpha ("Enable External Alpha", Float) = 0
13.     }
14.  
15.     SubShader
16.     {
17.         Tags
18.         {
19.             "Queue"="Transparent"
20.             "IgnoreProjector"="True"
21.             "RenderType"="Transparent"
22.             "PreviewType"="Plane"
23.             "CanUseSpriteAtlas"="True"
24.         }
25.  
26.         Cull Off
27.         Lighting Off
28.         ZWrite Off
29.         Blend One OneMinusSrcAlpha
30.  
31.         //stencil operation
32.         Stencil{
33.             Ref 1
34.             Comp Always
35.             Pass Replace
36.         }
37.  
38.         Pass
39.         {
40.             CGPROGRAM
41.                 #pragma vertex SpriteVert
42.                 #pragma fragment SpriteFrag
43.                 #pragma target 2.0
44.                 #pragma multi_compile_instancing
45.                 #pragma multi_compile_local _ PIXELSNAP_ON
46.                 #pragma multi_compile _ ETC1_EXTERNAL_ALPHA
47.                 #include "UnitySprites.cginc"
48.             ENDCG
49.         }
50.     }
51. }

Then, I created a 3D Plane with a mark texture, and added the following to the shader:

Code (CSharp):

1.  
2. Stencil
3. {
4.      Ref 1
5.      Comp Equal
6. }
7.  

It is working as expected except for one problem. Although the sprite mask is shown as circle, when the stencil effect is used, it appears not as circle but a figure with edges/faces. Can anyone give a hint how to fix it?

Thanks!