fix(shiftedOpacity): Do not shift opacity values of 0

Kitware · Nov 7, 2023 · 0b2600b · 0b2600b
1 parent c601192
commit 0b2600b
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Showing 2 changed files with 12 additions and 2 deletions.
diff --git a/src/utils/vtk-helpers.ts b/src/utils/vtk-helpers.ts
@@ -129,7 +129,13 @@ export function getShiftedOpacityFromPreset(
 
     const [xmin, xmax] = effectiveRange;
     const width = xmax - xmin;
-    return points.map(([x, y]) => [(x - xmin) / width + shift, y - shiftAlpha]);
+    return points.map(([x, y]) => {
+      // Non-zero values should be affected by shift
+      // but preset values of zero should not
+      const shifted = y - shiftAlpha;
+      const yVal = y || shifted ? shifted : -1;
+      return [(x - xmin) / width + shift, yVal];
+    });
   }
   return null;
 }

diff --git a/src/vtk/PiecewiseWidget/index.js b/src/vtk/PiecewiseWidget/index.js
@@ -52,7 +52,11 @@ export function samplePiecewiseLinear(
       } else if (slope === -Infinity) {
         sampledPoints.push(0);
       } else {
-        sampledPoints.push(slope * (sx - p1[0]) + (p1[1] - shiftAlpha));
+        // Non-zero values should be affected by shift
+        // but original values of zero should not
+        const shifted = p1[1] - shiftAlpha;
+        const y = p1[1] || shifted ? shifted : -1;
+        sampledPoints.push(slope * (sx - p1[0]) + y);
       }
     }
   }