Work on distortions

shader/texture/barrel.vert

@@ -1,5 +1,5 @@
 #version 450 core
-struct DataS { vec2 pos; vec2 v1; vec2 v2; vec2 rad; };
+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;
@@ -15,32 +15,41 @@ const vec2 cs[4] =
     , vec2 (-1, 1)
     , vec2 ( 1, 1)
     };
+vec2 f (vec2 p) // transforms a vector from "world" into "screen" space
+{ return (theMat * vec4(p,0,1) - theMat * vec4(0,0,0,1)).xy; }
+vec2 g (vec2 p)
+{ return normalize(p); }
+vec2 ncToTex (vec2 p) {return 0.5 * (p + 1);}
+mat4 toTransMat (vec2 p)
+{ return mat4
+    (  1,  0, 0 ,0
+    ,  0,  1, 0 ,0
+    ,  0,  0, 1 ,0
+    ,p.x,p.y, 0 ,1
+    ) ;
+}
 void main()
 {
   int k = ks[gl_VertexID];
-  vec4 off = (theMat * vec4(data[gl_VertexID/6].pos, 0,1));
-  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)
-//                   );
+  DataS thedata = data[gl_VertexID/6];
+  vec4 off = theMat * vec4(data[gl_VertexID/6].pos, 0,1);
+  vec2 r1 = f(thedata.v1);
+  vec2 r2 = f(thedata.v2);
   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));
+  vec4 pinchx = theMat 
+      * toTransMat(thedata.t3) 
+      * toTransMat(thedata.pos)
+      * mat4
+        (thedata.t1 , 0, 0
+        ,thedata.t2 , 0, 0
+        , 0,      0 , 0, 0
+        , 0,      0 , 0, 1
+        )
+      * inverse(toTransMat(thedata.pos))
+      * inverse(theMat) 
+      * (vec4(cs[k],0,1));
+  pinch = ncToTex(pinchx.xy) - ncToTex(cs[k]);
+  texPos = ncToTex(cs[k]);
   gl_Position = vec4 (cs[k],0,1);
 }