[FIX] fixed severe bug where vectors on surfaces got clipped although they are in the render plane

src/modules/imageSpaceLIC/shaders/WMImageSpaceLIC-Transformation-fragment.glsl

@@ -108,7 +108,7 @@ void main()
         discard;
     }
 
-    // project the vectors to image space
+    // project the vectors to image space as the input vector is in the tangent space
     vecProjected = projectVector( vec ).xyz;
 
 #endif
@@ -152,19 +152,12 @@ void main()
     // if( isZero( cmap.r - 1.0, 0.15 ) )
     //     gl_FragData[1] = vec4( 1.0, 0.0, 0.0, 1.0 );
     // }
+    gl_FragData[1] = colormapping();
 
-    // is the vector very orthogonal to the surface?
+    // is the vector very orthogonal to the surface? We scale our advection according to this.
+    float dotS = abs( dot( v_normal, vec.xyz ) );
+    vec2 dotScaled = ( 1.0 - dotS ) * scaleMaxToOne( vecProjected ).xy;
 
-    float dotS = dot( v_normal, vec.xyz );
-    vec2 dotScaled = ( 1.0 + sign( dotS ) ) * scaleMaxToOne( vecProjected ).xy;
-    // MPI Paper Hack;
-    // dotScaled = 40.0*vecProjected.xy;
     gl_FragData[0] = vec4( vec2( 0.5 ) + ( 0.5  * dotScaled ), light, noise3D );
-
-    // MPI PAper Hack:
-    // {
-    // //gl_FragData[1] = colormapping();
-    // }
-    gl_FragData[1] = colormapping();
 }
 

src/modules/imageSpaceLIC/shaders/WMImageSpaceLIC-Transformation-varyings.glsl

@@ -27,6 +27,11 @@
  */
 varying vec3 v_normal;
 
+/**
+ * The normal interpolated and projected to screenspace
+ */
+varying vec3 v_normalProjected;
+
 /**
  * The light source in local coordinates
  */

src/modules/imageSpaceLIC/shaders/WMImageSpaceLIC-Transformation-vertex.glsl

@@ -33,12 +33,12 @@
 /**
  * How much should the slice be moved along u_vertexShiftDirection?
  */
-uniform int u_vertexShift;
+uniform int u_vertexShift = 0;
 
 /**
  * The direction along which the slice gets moved
  */
-uniform vec3 u_vertexShiftDirection;
+uniform vec3 u_vertexShiftDirection = vec3( 0.0, 0.0, 0.0 );
 
 /**
  * Size of input texture in pixels
@@ -96,6 +96,10 @@ void main()
     // some light precalculations
     v_normal = gl_Normal;
 
+    // NOTE: we normalize the vec here although we need to normalize it again in the fragment shader since the projected vector might be very
+    // small and we want to avoid numerical issues when interpolating.
+    v_normalProjected = normalize( projectVector( vec4( gl_Normal.xyz, 0.0 ) ) );
+
     // if we use 3d noise textures and auto resolution feature:
 #ifdef NOISE3D_ENABLED
     vec4 vec1 = vec4( float( u_texture0SizeX ) / float( u_texture1SizeX ),