Volume shader tricubic filtering bugfix for WebGL

lavavu · Jul 12, 2018 · 6b033a6 · 6b033a6
1 parent 13679c0
commit 6b033a6
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Showing 2 changed files with 30 additions and 34 deletions.
diff --git a/lavavu/html/viewer.html b/lavavu/html/viewer.html
@@ -536,19 +536,26 @@
 
 #ifdef WEBGL
 
-vec2 islices;
-float maxslice;
-vec2 cmin;
-vec2 cmax;
+vec2 islices = vec2(1.0 / slices.x, 1.0 / slices.y);
+float maxslice = slices.x * slices.y - 1.0;
+vec2 cmin = vec2(0.5/(slices.x*slices.y), 0.5/(slices.x*slices.y));
+vec2 cmax = vec2(1.0, 1.0) - cmin;
+
 
 float sample(vec3 pos)
 {
   //Get z slice index and position between two slices
   float Z = pos.z * maxslice;
   float slice = floor(Z); //Index of first slice
   Z = fract(Z);
+  //Edge case at z min (possible with tricubic filtering)
+  if (int(slice) < 0)
+  {
+    slice = 0.0;
+    Z = 0.0;
+  }
   //Edge case at z max
-  if (int(slice) > int(maxslice)-1)
+  else if (int(slice) > int(maxslice)-1)
   {
     slice = maxslice-1.0;
     Z = 1.0;
@@ -602,10 +609,8 @@
 }
 
 #else
-float sample(vec3 pos)
-{
-  return texture3D(uVolume, pos).x;
-}
+
+#define sample(pos) texture3D(uVolume, pos).x
 
 float tex3D(vec3 pos)
 {
@@ -615,7 +620,7 @@
     density = interpolate_tricubic_fast(pos);
   else
 #endif
-    density = sample(pos);
+    density = texture3D(uVolume, pos).x;
 
   //Normalise the density over provided range
   //(used for float textures only, all other formats are already [0,1])
@@ -684,13 +689,6 @@
     bbMin = clamp(uBBMin, vec3(0.0), vec3(1.0));
     bbMax = clamp(uBBMax, vec3(0.0), vec3(1.0));
 
-#ifdef WEBGL
-    islices = vec2(1.0 / slices.x, 1.0 / slices.y);
-    maxslice = slices.x * slices.y - 1.0;
-    cmin = vec2(0.5/(slices.x*slices.y), 0.5/(slices.x*slices.y));
-    cmax = vec2(1.0, 1.0) - cmin;
-#endif
-
     //Compute eye space coord from window space to get the ray direction
     mat4 invMVMatrix = transpose(uMVMatrix);
     //ObjectSpace *[MV] = EyeSpace *[P] = Clip /w = Normalised device coords ->VP-> Window

diff --git a/lavavu/shaders/volumeShader.frag b/lavavu/shaders/volumeShader.frag
@@ -61,19 +61,26 @@ float interpolate_tricubic_fast(vec3 coord);
 
 #ifdef WEBGL
 
-vec2 islices;
-float maxslice;
-vec2 cmin;
-vec2 cmax;
+vec2 islices = vec2(1.0 / slices.x, 1.0 / slices.y);
+float maxslice = slices.x * slices.y - 1.0;
+vec2 cmin = vec2(0.5/(slices.x*slices.y), 0.5/(slices.x*slices.y));
+vec2 cmax = vec2(1.0, 1.0) - cmin;
+
 
 float sample(vec3 pos)
 {
   //Get z slice index and position between two slices
   float Z = pos.z * maxslice;
   float slice = floor(Z); //Index of first slice
   Z = fract(Z);
+  //Edge case at z min (possible with tricubic filtering)
+  if (int(slice) < 0)
+  {
+    slice = 0.0;
+    Z = 0.0;
+  }
   //Edge case at z max
-  if (int(slice) > int(maxslice)-1)
+  else if (int(slice) > int(maxslice)-1)
   {
     slice = maxslice-1.0;
     Z = 1.0;
@@ -127,10 +134,8 @@ mat4 transpose(in mat4 m)
 }
 
 #else
-float sample(vec3 pos)
-{
-  return texture3D(uVolume, pos).x;
-}
+
+#define sample(pos) texture3D(uVolume, pos).x
 
 float tex3D(vec3 pos)
 {
@@ -140,7 +145,7 @@ float tex3D(vec3 pos)
     density = interpolate_tricubic_fast(pos);
   else
 #endif
-    density = sample(pos);
+    density = texture3D(uVolume, pos).x;
 
   //Normalise the density over provided range
   //(used for float textures only, all other formats are already [0,1])
@@ -209,13 +214,6 @@ void main()
     bbMin = clamp(uBBMin, vec3(0.0), vec3(1.0));
     bbMax = clamp(uBBMax, vec3(0.0), vec3(1.0));
 
-#ifdef WEBGL
-    islices = vec2(1.0 / slices.x, 1.0 / slices.y);
-    maxslice = slices.x * slices.y - 1.0;
-    cmin = vec2(0.5/(slices.x*slices.y), 0.5/(slices.x*slices.y));
-    cmax = vec2(1.0, 1.0) - cmin;
-#endif
-
     //Compute eye space coord from window space to get the ray direction
     mat4 invMVMatrix = transpose(uMVMatrix);
     //ObjectSpace *[MV] = EyeSpace *[P] = Clip /w = Normalised device coords ->VP-> Window