Allow transparent segmentations

Author: mlavik1

Assets/Scripts/VolumeObject/VolumeRenderedObject.cs

@@ -254,17 +254,19 @@ public void UpdateSegmentationLabels()
             float minDataValue = secondaryDataset.GetMinDataValue();
             float maxDataValue = secondaryDataset.GetMaxDataValue();
             secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(0.0f, 0.0f));
-            secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(1.0f, 1.0f));
             for (int i = 0; i < segmentationLabels.Count; i++)
             {
                 SegmentationLabel segmentationLabel = segmentationLabels[i];
                 float t = segmentationLabel.id / maxDataValue;
+                float segmAlpha = segmentationLabel.colour.a;
                 secondaryTransferFunction.colourControlPoints.Add(new TFColourControlPoint(t, segmentationLabel.colour));
-                if (i == 0)
-                {
-                    secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(t - 0.01f, 0.0f));
-                    secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(t, 1.0f));
-                }
+                if (t > 0.0f)
+                    secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(Mathf.Max(t - 0.001f, 0.0f), segmAlpha));
+                secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(t, segmAlpha));
+                if (i == segmentationLabels.Count - 1)
+                    secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(1.0f, segmAlpha));
+                else
+                    secondaryTransferFunction.alphaControlPoints.Add(new TFAlphaControlPoint(t + 0.001f, segmAlpha));
             }
             secondaryTransferFunction.GenerateTexture();
             secondaryTransferFunction.GetTexture().filterMode = FilterMode.Point;

Assets/Shaders/DirectVolumeRenderingShader.shader

@@ -476,13 +476,17 @@
                     const float secondaryDensity = getSecondaryDensity(currPos);
                     if (secondaryDensity > 0.0)
                     {
-                        col = getSecondaryTF1DColour(secondaryDensity);
-                        float3 gradient = getGradient(currPos);
-                        float gradMag = length(gradient);
-                        float3 normal = gradient / gradMag;
-                        col.rgb = calculateLighting(col.rgb, normal, getLightDirection(-ray.direction), -ray.direction, 0.15);
-                        col.a = 1.0;
-                        break;
+                        float4 secondaryColour = getSecondaryTF1DColour(secondaryDensity);
+                        if (secondaryColour.a > 0.0)
+                        {
+                            col = secondaryColour;
+                            float3 gradient = getGradient(currPos);
+                            float gradMag = length(gradient);
+                            float3 normal = gradient / gradMag;
+                            col.rgb = calculateLighting(col.rgb, normal, getLightDirection(-ray.direction), -ray.direction, 0.15);
+                            col.a = 1.0;
+                            break;
+                        }
                     }
 #endif
                     if (density > _MinVal && density < _MaxVal)