codding UV for get best resault in pinching

hello
for first , i'm sorry for My bad thread title ( i don't know what i should say if you can change it )

i have a 2D project but im my project we need change the vertex position

i have problem because my Plane made from 4 vertex and if i want change the position of both vertex in right
i get bad resault

like up-right plane in the uploaded image

anybody have any way to get resault like down-right plane in the image?

my used code to generate up-right plane is a normaly way

Code (csharp):

1.  
2. Mesh1.vertices = new Vector3[] { sphere1.position, sphere2.position,  sphere3.position, sphere4.position};
3.             Mesh1.triangles = new int[] { 0, 1, 3, 0, 3, 2 };
4.             Mesh1.uv = new Vector2[] { new Vector2(0,0), new Vector2(0,1)
5.                                     , new Vector2(1, 1), new Vector2(1, 0)
6.             };
7.  

 

acourding to this page there is no way
http://answers.unity3d.com/questions/1091692/texture-on-custom-mesh-splits-at-edge.html
acording to this pdf ( i cant understand true what say)
http://web.cs.ucdavis.edu/~amenta/s12/perspectiveCorrect.pdf
i hope can get correct result with help of the blow link
http://stackoverflow.com/questions/12414708/correct-glsl-affine-texture-mapping/12439387#12439387

 

after many try and search i found a good way to get my resault
i use this C# code


thanx to Jessy for good thread

Code (csharp):

1.  
2.  
3.             Mesh1.vertices = new Vector3[] { sphere1.position, sphere2.position, sphere3.position, sphere4.position };
4.             Mesh1.triangles = new int[] { 0, 1, 2, 0, 2, 3 };  
5.  
6.             Vector3[] vertices = Mesh1.vertices;
7.  
8.             var shiftedPositions = new Vector2[] {
9.                new Vector2(0 ,0),
10.                new Vector2(0, vertices[1].y - vertices[0].y),
11.                new Vector2(Mathf.Abs(vertices[0].x - vertices[3].x) , vertices[2].y - vertices[3].y),
12.                new Vector2(Mathf.Abs(vertices[0].x - vertices[3].x) , 0)
13.            };
14.  
15.             var keshesh = Mathf.Abs(vertices[3].x - vertices[0].x)  ;
16.  
17.             Debug.Log(keshesh);
18.  
19.             Mesh1.uv = shiftedPositions;
20.  
21.             var widths_heights = new Vector2[4];
22.             widths_heights[0].x = widths_heights[3].x = shiftedPositions[3].x / keshesh;
23.             widths_heights[1].x = widths_heights[2].x = shiftedPositions[3].x / keshesh;
24.             widths_heights[0].y = widths_heights[1].y = shiftedPositions[1].y;
25.             widths_heights[2].y = widths_heights[3].y = shiftedPositions[2].y;
26.            
27.             Mesh1.uv2 = widths_heights;
28.  

and this shader

Code (csharp):

1.  
2. Shader "Custom/UVfixing" {
3.    
4.     Properties {
5.    
6.         _MainTex ("Base (RGB)", 2D) = "white" {}
7.     }
8.    
9.     SubShader {
10.        Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
11.         LOD 400
12.         ZWrite Off
13.         ColorMask RGB
14.         pass{
15.             CGPROGRAM
16.  
17.             uniform sampler2D _MainTex;
18.            
19.             #pragma vertex vert            
20.             #pragma fragment frag
21.            
22.  
23.         struct vertexInput {
24.             float4 vertex : POSITION;          
25.             float4 texcoord  : TEXCOORD0;
26.             float4 texcoord1  : TEXCOORD1;        
27.         };
28.  
29.         struct vertexOutput {
30.             float4 pos : SV_POSITION;
31.             float2 uv  : TEXCOORD0;
32.             float2 uv2  : TEXCOORD1;          
33.         };
34.  
35.         vertexOutput vert(vertexInput input)
36.         {
37.             vertexOutput output;
38.             output.pos = mul(UNITY_MATRIX_MVP,  input.vertex);
39.            
40.             output.uv = input.texcoord;
41.             output.uv2  = input.texcoord1 ;
42.            
43.             return output;
44.         }
45.  
46.         float4 frag(vertexOutput input) : COLOR
47.         {      
48.             return  tex2D(_MainTex, float2(input.uv)/float2(input.uv2 ));      
49.         }
50.        
51.          ENDCG
52.     }
53.     }
54.    
55. }
56.  

and get this resault


thanx allot all of masters