fix: Segmentation slice range is wrong when nearly orthonormal as well as for segmentation volumes

packages/core/src/loaders/volumeLoader.ts

@@ -454,6 +454,11 @@ export function registerVolumeLoader(
   volumeLoaders[scheme] = volumeLoader;
 }
 
+/** Gets the array of volume loader schemes */
+export function getVolumeLoaderSchemes(): string[] {
+  return Object.keys(volumeLoaders);
+}
+
 /**
  * Registers a new unknownVolumeLoader and returns the previous one
  *

packages/core/src/utilities/getSliceRange.ts

@@ -1,8 +1,9 @@
 import vtkMatrixBuilder from '@kitware/vtk.js/Common/Core/MatrixBuilder';
 import getVolumeActorCorners from './getVolumeActorCorners';
 import type { VolumeActor, Point3, ActorSliceRange } from '../types';
+import { EPSILON } from '../constants';
 
-const isOne = (v) => Math.abs(v) > 0.99 && Math.abs(v) < 1.01;
+const isOne = (v) => Math.abs(Math.abs(v) - 1) < EPSILON;
 const isUnit = (v, off) =>
   isOne(v[off]) || isOne(v[off + 1]) || isOne(v[off + 2]);
 

packages/core/src/utilities/getTargetVolumeAndSpacingInNormalDir.ts

@@ -3,10 +3,22 @@ import { EPSILON } from '../constants';
 // import type { VolumeViewport } from '../RenderingEngine'
 import { ICamera, IImageVolume, IVolumeViewport } from '../types';
 import getSpacingInNormalDirection from './getSpacingInNormalDirection';
+import { getVolumeLoaderSchemes } from '../loaders/volumeLoader';
 
 // One EPSILON part larger multiplier
 const EPSILON_PART = 1 + EPSILON;
 
+const startsWith = (str, starts) =>
+  starts === str.substring(0, Math.min(str.length, starts.length));
+
+// Check if this is a primary volume
+// For now, that means it came from some sort of image loader, but
+// should be specifically designated.
+const isPrimaryVolume = (volume): boolean =>
+  !!getVolumeLoaderSchemes().find((scheme) =>
+    startsWith(volume.volumeId, scheme)
+  );
+
 /**
  * Given a volume viewport and camera, find the target volume.
  * The imageVolume is retrieved from cache for the specified targetVolumeId or
@@ -82,9 +94,16 @@ export default function getTargetVolumeAndSpacingInNormalDir(
     actorUID: null,
   };
 
+  const hasPrimaryVolume = imageVolumes.find(isPrimaryVolume);
+
   for (let i = 0; i < imageVolumes.length; i++) {
     const imageVolume = imageVolumes[i];
 
+    if (hasPrimaryVolume && !isPrimaryVolume(imageVolume)) {
+      // Secondary volumes like segmentation don't count towards spacing
+      continue;
+    }
+
     const spacingInNormalDirection = getSpacingInNormalDirection(
       imageVolume,
       viewPlaneNormal