Get standard uvs for 9 sliced image shader

I'm woking on UI shaders and noticed that the uvs I get from a simple image as input differ from the ones from a 9-sliced image. This totally makes sense, but I wasn't expecting it. I'm wondering if there is a way to still get the simple uv data in the shader.
Comparison:

Spoiler: Shader code

Code (CSharp):

1. Shader "UI/Simple UV"
2. {
3.     Properties
4.     {
5.         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
6.         _Color ("Tint", Color) = (1,1,1,1)
7.     }
8.  
9.     CGINCLUDE
10.     #include "UnityCG.cginc"
11.     #include "UnityUI.cginc"
12.    
13.     fixed4 _Color;
14.     fixed4 _TextureSampleAdd;
15.    
16.     struct appdata_t
17.     {
18.         float4 vertex   : POSITION;
19.         float4 color    : COLOR;
20.         float2 texcoord : TEXCOORD0;
21.     };
22.  
23.     struct v2f
24.     {
25.         float4 vertex   : SV_POSITION;
26.         fixed4 color    : COLOR;
27.         half2 texcoord  : TEXCOORD0;
28.     };
29.    
30.     v2f vert(appdata_t IN)
31.     {
32.         v2f OUT;
33.         OUT.vertex = UnityObjectToClipPos(IN.vertex);
34.  
35.         OUT.texcoord = IN.texcoord;
36.        
37.         #ifdef UNITY_HALF_TEXEL_OFFSET
38.         OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
39.         #endif
40.        
41.         OUT.color = IN.color * _Color;
42.         return OUT;
43.     }
44.  
45.     sampler2D _MainTex;
46.     fixed4 frag(v2f IN) : SV_Target
47.     {
48.         return (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color * half4(IN.texcoord.xy, 0.0, 1.0);
49.     }
50.     ENDCG
51.    
52.     SubShader
53.     {
54.         Tags
55.         {
56.             "Queue"="Transparent"
57.             "IgnoreProjector"="True"
58.             "RenderType"="Transparent"
59.             "PreviewType"="Plane"
60.             "CanUseSpriteAtlas"="True"
61.         }
62.  
63.         Cull Off
64.         Lighting Off
65.         ZWrite Off
66.         ZTest [unity_GUIZTestMode]
67.         Blend SrcAlpha OneMinusSrcAlpha
68.  
69.         Pass
70.         {
71.         CGPROGRAM
72.             #pragma vertex vert
73.             #pragma fragment frag
74.         ENDCG
75.         }
76.     }
77. }

 

I have this problem too, did you ever solve it?
Thanks

 

Nope, I didn't need it in the end. But from working quite a bit on ui shaders,I recommend checking out MeshModifiers: https://docs.unity3d.com/ScriptReference/UI.BaseMeshEffect.html
With those you should be easily able to do what you want to do (e.g. put the original uv information in the vertex color).

 

There's a simple solution to this that is probably sufficient for most cases. At least it works in mine.

In the vertex shader:

Code (CSharp):

1. float2 baseUv = float2(0, 0);
2. baseUv.x = slicedUv.x > 0.5 ? 1 : 0;
3. baseUv.y = slicedUv.y > 0.5 ? 1 : 0;

This works on the following assumptions:
1. You're using this material on a UI element that only has 4 vertices (1 in each corner)
2. The sliced _MainTex borders do not exceed 50% of the texture size

 

Unity's 9 slice UI elements work by actually slicing the mesh into 9 quads, so it's a mesh with 16 vertices, not 4, hence why this isn't solvable by applying a shader to a sprite already set to use the built in 9-slice support. It'll also break on any atlased sprite as their UVs are not necessarily in a 0.0 to 1.0 range, so that 0.5 test won't work there either.

 

Yeah, as I played around with it more I discovered it's a truly flimsy solution. :-/
Seems like there should be an easier way to do this...

I guess one way would be to calculate bottom-left, top-right vertex in CS, then set those values on the material and use them to infer the UV in the vertex shader.

 

As already pointed out, ui elements have a very nice base class with which you can do all kind of magic without the need of setting material properties

 

Here's one that works for me
Just make sure in the shader you are looking at vertex color channel Red instead of U coordinates.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using System.Linq;
4. using UnityEngine;
5. using UnityEngine.Pool;
6. using UnityEngine.UI;
7.  
8. public class ImageSliceWithUV : BaseMeshEffect
9. {
10.  
11.     protected ImageSliceWithUV()
12.     {}
13.    
14.     public override void ModifyMesh(VertexHelper vh)
15.     {
16.         List<UIVertex> verts = new List<UIVertex>();
17.         vh.GetUIVertexStream(verts);
18.  
19.         var orderedVerts = verts.OrderBy(v => v.position.x).ToList();
20.         var minX = orderedVerts.First().position.x;
21.         var maxX = orderedVerts.Last().position.x;
22.                                      
23.         for (int i = 0; i < verts.Count; i++)
24.         {
25.             UIVertex vertex = verts[i];
26.             Vector3 position = vertex.position;
27.            
28.             vertex.color.r = (byte)(Mathf.InverseLerp(minX, maxX, position.x) * 255);
29.             verts[i] = vertex;
30.         }
31.  
32.         vh.Clear();
33.         vh.AddUIVertexTriangleStream(verts);
34.     }
35. }
36.