Work on distortion shader

shader/texture/barrel.vert

@@ -1,9 +1,10 @@
 #version 450 core
-struct DataS { vec2 pos; vec2 rad1; vec2 rad2; };
+struct DataS { vec2 pos; vec2 v1; vec2 v2; vec2 rad; };
 layout (std430, binding = 9) readonly buffer Data { DataS data[]; };
 layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
 out vec2 texPos;
 out vec2 distmask;
+out vec2 pinch;
 const int ks[6] =   
     {0,1,2          //  2--3
     ,2,1,3          //  |  |
@@ -18,10 +19,28 @@ void main()
 {
   int k = ks[gl_VertexID];
   vec4 off = (theMat * vec4(data[gl_VertexID/6].pos, 0,1));
-  float r = distance
-        ((theMat * vec4(data[gl_VertexID/6].rad1, 0,1)).xy
-        ,(theMat * vec4(0,0, 0,1)).xy);
-  distmask = (cs[k] - off.xy)/r;
+  vec2 r1 = (theMat * vec4(data[gl_VertexID/6].v1, 0,1)).xy
+            - (theMat * vec4(0,0,0,1)).xy;
+  vec2 r2 = (theMat * vec4(data[gl_VertexID/6].v2, 0,1)).xy
+            - (theMat * vec4(0,0, 0,1)).xy;
+  pinch = 
+        (theMat * vec4(data[gl_VertexID/6].rad, 0,1)).xy
+        - (theMat * vec4(0,0, 0,1)).xy;
+//  mat2 distT = mat2(-1/r1.x, -1/r2.x
+//                   ,1/r1.y, -1/r2.y
+//                   );
+//  mat2 distT = mat2(2, 0
+//                   ,-1/sqrt(2), 1/sqrt(2)
+//                   );
+//  mat2 distT = mat2(1/r1.x, 2*sqrt(2)
+//                    ,1/r1.y, 2*sqrt(2)
+//                   );
+  mat2 distT = inverse (mat2(r1,r2));
+//  mat2 distT = mat2(1/r1.x, 1/r2.x
+//                   ,1/r1.y, 1/r2.y
+//                   );
+  //distmask = (cs[k] - off.xy)/r;
+  distmask = distT * (cs[k] - off.xy);
   texPos = 0.5 * (cs[k]+vec2(1,1));
   gl_Position = vec4 (cs[k],0,1);
 }