Implement (not fully working) alternate shadow volumes

shader/lighting/lineShadow.geom

@@ -3,9 +3,10 @@ layout (lines_adjacency) in;
 layout (triangle_strip, max_vertices = 4) out;
 layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
 uniform vec3 lightPos;
-uniform vec4 lumRad;
+uniform float radiusUniform;
 //vec4 shift (vec4 p) { return (vec4 (p.xyz + (lumRad.a*normalize(p.xyz-lightPos)), 1));}
 vec4 shift (vec4 p) { return (vec4 (p.xyz + (100000*(p.xyz-lightPos)), 1));}
+vec4 shiftBy (float x,vec4 p) { return (vec4 (lightPos + (x*normalize(p.xyz-lightPos)), 1));}
 //vec4 shift (vec4 p) { return (vec4 (lightPos + (lumRad.a*normalize(p.xyz-lightPos)), 1));}
 // copied from lighting/cap.geom, should not be changed on its own
 vec4 projNear (vec4 pos)
@@ -18,6 +19,7 @@ vec4 projNear (vec4 pos)
     return vec4 ( xy, 140 , 1) ;
 }
 vec4 shiftNear (vec4 pos)
+//{ vec4 sp = shiftBy(radiusUniform,pos);
 { vec4 sp = shift(pos);
     if (sp.z > 140)
     { return projNear(pos) ; }
@@ -27,6 +29,7 @@ vec4 shiftNear (vec4 pos)
 vec4 f (vec4 p) {return (theMat * p);}
 void main()
 {
+    float ru2 = radiusUniform * radiusUniform ;
     vec4 p0 = gl_in[0].gl_Position;
     vec4 p1 = gl_in[1].gl_Position;
     vec4 mid = 0.5*(p0 + p1);
@@ -41,7 +44,8 @@ void main()
     // first test if the edge is part of the silhouette
     // that is, if the normals of the faces connected by the edge point are in
     // "different directions" wrt the light direction
-    if ( dot(n0 , lightDir) * dot(n1 , lightDir) <= 0 )
+    if ( dot(n0 , lightDir) * dot(n1 , lightDir) <= 0 && 
+                (dot(lightDir,lightDir) < ru2 || dot(lightDir2,lightDir2) < ru2) )
                 // using <= rather than < seems to get rid of overlapping shadow
                 // artefacts
     {