Allow for multiple distortions at once

shader/texture/barrel.vert

@@ -3,8 +3,8 @@ struct DataS { vec2 pos; vec2 v1; vec2 v2; vec2 t1; vec2 t2; vec2 t3; };
 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;
+out vec2 distmask[2];
+out vec2 pinch[2];
 const int ks[6] =   
     {0,1,2          //  2--3
     ,2,1,3          //  |  |
@@ -31,12 +31,14 @@ mat4 toTransMat (vec2 p)
 void main()
 {
   int k = ks[gl_VertexID];
-  DataS thedata = data[gl_VertexID/6];
-  vec4 off = theMat * vec4(data[gl_VertexID/6].pos, 0,1);
+  for(int i = 0; i < 2; ++i)
+  {
+  vec4 off = theMat * vec4(data[i + gl_VertexID/6].pos, 0,1);
+  DataS thedata = data[i + gl_VertexID/6];
   vec2 r1 = f(thedata.v1);
   vec2 r2 = f(thedata.v2);
   mat2 distT = inverse (mat2(r1,r2));
-  distmask = distT * (cs[k] - off.xy);
+  distmask[i] = (distT * (cs[k] - off.xy));
   vec4 pinchx = theMat 
       * toTransMat(thedata.t3) 
       * toTransMat(thedata.pos)
@@ -49,7 +51,8 @@ void main()
       * inverse(toTransMat(thedata.pos))
       * inverse(theMat) 
       * (vec4(cs[k],0,1));
-  pinch = ncToTex(pinchx.xy) - ncToTex(cs[k]);
+  pinch[i] = ncToTex(pinchx.xy) - ncToTex(cs[k]);
+  }
   texPos = ncToTex(cs[k]);
   gl_Position = vec4 (cs[k],0,1);
 }