RF: Do not modulate vector opacity by vector magnitude. Do not display vectors

with length 0 or NaN values.

fsleyes/assets/gl/gl14/glvector_frag.prog

@@ -88,9 +88,9 @@ PARAM zColour      = {{ param_zColour         }};
 PARAM colourXform  = {{ param_colourXform     }};
 
 
-# Bail if the textureq coordinate
+# Bail if the texture coordinate
 # is out of the image space.
-# We use voxValue out of convenience
+# We use voxValue as a temporary
 {{
 arb_call('textest.prog',
          texCoord='{{ varying_vecTexCoord }}',
@@ -105,6 +105,26 @@ TEX voxValue,  {{ varying_vecTexCoord  }}, {{ texture_vectorTexture   }}, 3D;
 TEX modValue,  {{ varying_modTexCoord  }}, {{ texture_modulateTexture }}, 3D;
 TEX clipValue, {{ varying_clipTexCoord }}, {{ texture_clipTexture     }}, 3D;
 
+# Kill the fragment if this vector
+# has length 0 or contains NaNs
+# We use clipResult as a temporary
+# kill if length is 0
+DP3 clipResult.x, voxValue, voxValue;
+MUL clipResult.x, clipResult.x, -1;
+SGE clipResult.x, clipResult.x, 0;
+MUL clipResult.x, clipResult.x, -1;
+KIL clipResult.x;
+# kill if vector contains NaNs.
+# There is no nan test, or equality
+# test, so we test whether
+# (value >= value) || (value < value)
+DP3 clipResult.x, voxValue, voxValue;
+SGE clipResult.y, clipResult.x, clipResult.x;
+SLT clipResult.z, clipResult.x, clipResult.x;
+ADD clipResult.x, clipResult.y, clipResult.z;
+SUB clipResult.x, clipResult.x, 0.5;
+KIL clipResult.x;
+
 # Clobber the clipping/modulation
 # values we just looked up if their
 # texture coords were out of bounds.
@@ -165,10 +185,11 @@ ABS voxValue, voxValue;
 
 # Cumulatively combine the rgb
 # channels of those three colours
-MOV fragColour, 0;
-MAD fragColour, voxValue.x, xColour, fragColour;
-MAD fragColour, voxValue.y, yColour, fragColour;
-MAD fragColour, voxValue.z, zColour, fragColour;
+MOV fragColour,   0;
+MAD fragColour,   voxValue.x, xColour, fragColour;
+MAD fragColour,   voxValue.y, yColour, fragColour;
+MAD fragColour,   voxValue.z, zColour, fragColour;
+MOV fragColour.w, xColour.w;
 
 # Apply the bri/con scale and offset
 MAD fragColour.rgb, fragColour, colourXform.x, colourXform.y;

fsleyes/assets/gl/gl21/glvector_frag.glsl

@@ -142,6 +142,12 @@ void main(void) {
     voxValue = texture3D(vectorTexture, fragVecTexCoord).xyz;
   }
 
+  /* Do not draw vectors with length 0 or with NaNs */
+  float len = length(voxValue.xyz);
+  if (len == 0 || len != len) {
+    discard;
+  }
+
   /* Look up the modulation and clipping values */
   float modValue;
   float clipValue;
@@ -199,10 +205,15 @@ void main(void) {
   voxValue += voxValXform[3].x;
   voxValue  = abs(voxValue);
 
-  /* Combine the xyz component colours. */
+  /*
+   * Combine the xyz component colours.
+   * Opacity should be ident0ical across
+   * the three colours.
+   */
   vec4 voxColour = voxValue.x * xColour +
                    voxValue.y * yColour +
                    voxValue.z * zColour;
+  voxColour.a    = xColour.a;
 
   /*
    * Apply the colour scale/offset -