cutaway shader using discard

Hi, i tried to write a cutaway shader to get the effect here http://gm-cdn.gamezebo.netdna-cdn.com/wp-content/uploads/2015/02/overland-windmill-600x4201.jpg, i attatched the result i got.

i result i got does not render inside faces as you can see(like a cross section), also i want to use a solid color for ground at the cutaway like in the example above.

this is the code for it - (i modified a toon shader) using discard to stop rendering fragments after a certain distance(x,y,z directions) from a gameobject(blue cube) that i control.

Code (CSharp):

1. fragmentInput vert(vertexInput i){
2.                     fragmentInput o;
3.                     o.pos = mul(UNITY_MATRIX_MVP, i.vertex);
4.                     o.uv = TRANSFORM_TEX(i.texcoord, _MainTex);
5.                  
6.                      o.Pos_In_World_Coords = mul(_Object2World, i.vertex);
7.                     // Here we set up the normal and light dir for use in the fragment shader, both in object space.
8.                     o.normal = i.normal;
9.                     o.lightDir = ObjSpaceLightDir(i.vertex);
10.                     return o;
11.                 }
12.            
13.                 float4 frag(fragmentInput i) : COLOR
14.                 {
15.                     // Normalize the vectors to fix interpolation shortening.
16.                     i.normal = normalize(i.normal);
17.                     i.lightDir = normalize(i.lightDir);
18.                     // Get dot product to use as ramp UV coords.
19.                     // Transformed from -1 to 1 range to 0 - 1 range so it can use the full dimensions of the ramp texture.
20.                     float NdotL = dot(i.normal, i.lightDir) * 0.5 + 0.5;
21.                                      
22.                     // Put the vector maths in brackets so it doesn't try and do scalar-vector maths where it doesn't need to.
23.                     fixed4 c;
24.                     c.rgb = (tex2D(_MainTex, i.uv).rgb * tex2D(_RampTex, NdotL.xx).rgb * _LightColor0.rgb * _Color.rgb) * 2;
25.                     c.a = 1.0;
26.                  
27.                     if (abs(i.Pos_In_World_Coords.y - _Point.y) > _Distance || abs(i.Pos_In_World_Coords.x- _Point.x) > _Distance || abs(i.Pos_In_World_Coords.z - _Point.z) > _Distance)
28.                     {
29.                        discard; // drop the fragment if xyz coordinate > _Distance
30.                     }
31.                     return c;
32.                  
33.                  }

i found a thread similar to it in unreal forums https://forums.unrealengine.com/showthread.php?1441-Cross-Section-Shader-help-please , i dont know how to use opacity mask in code.

 

Try adding this after your Tags:

Code (CSharp):

1. Cull Off

 

it worked, if i dont want to show the interiors of cross section(ex: a thick ground plane) what to do?any idea?

 

It looks like you're looking for this:
http://forum.unity3d.com/threads/simple-cross-section-shader.34508/#post-1477352

 

i figured it out after going through that thread , they were doing the same thing with plane equation. Now i added shadows to it using this http://forum.unity3d.com/threads/adding-shadows-to-custom-shader-vert-frag.108612/
it still has a few problems:
-not able to change the color of the shadow
-still getting shadows for the entire object even though i cut it(second image)
For the second problem google says unity still thinks it has all the vertices and calculates the shadow accordingly, so i have to somehow skip the shadow calculation at those vertices.

Any thoughts?