Re #2127: make crosshair linked views rotations around the focus of the crosshair

Author: Punzo

src/VTKViewport/vtkInteractorStyleRotatableMPRCrosshairs.js

@@ -4,6 +4,7 @@ import Constants from 'vtk.js/Sources/Rendering/Core/InteractorStyle/Constants';
 import vtkCoordinate from 'vtk.js/Sources/Rendering/Core/Coordinate';
 import vtkMatrixBuilder from 'vtk.js/Sources/Common/Core/MatrixBuilder';
 import { vec2, vec3, quat } from 'gl-matrix';
+import vtkMath from 'vtk.js/Sources/Common/Core/Math';
 
 const { States } = Constants;
 
@@ -250,23 +251,69 @@ function vtkInteractorStyleRotatableMPRCrosshairs(publicAPI, model) {
     const sliceNormal = thisApi.getSliceNormal();
     const axis = [-sliceNormal[0], -sliceNormal[1], -sliceNormal[2]];
 
-    const { matrix } = vtkMatrixBuilder.buildFromRadian().rotate(angle, axis);
-
     // Rotate other apis
     apis.forEach((api, index) => {
       if (index !== apiIndex) {
-        // get normal and viewUp.
+        const cameraForApi = api.genericRenderWindow
+          .getRenderWindow()
+          .getInteractor()
+          .getCurrentRenderer()
+          .getActiveCamera();
+
+        const crosshairPointForApi = api.get('cachedCrosshairWorldPosition');
+        const initialCrosshairPointForApi = api.get(
+          'initialCachedCrosshairWorldPosition'
+        );
+
+        const center = [];
+        vtkMath.subtract(
+          crosshairPointForApi,
+          initialCrosshairPointForApi,
+          center
+        );
+        const translate = [];
+        vtkMath.add(crosshairPointForApi, center, translate);
+
+        const { matrix } = vtkMatrixBuilder
+          .buildFromRadian()
+          .translate(translate[0], translate[1], translate[2])
+          .rotate(angle, axis)
+          .translate(-translate[0], -translate[1], -translate[2]);
+
+        cameraForApi.applyTransform(matrix);
 
         const sliceNormalForApi = api.getSliceNormal();
         const viewUpForApi = api.getViewUp();
+        api.setOrientation(sliceNormalForApi, viewUpForApi);
+
+        /* After rotating the focal point line of sight coordinate is not on the crosshair.
+        Find nearest point of the crosshair to the line of sight of the camera*/
+
+        /*p1 = cameraPositionForApi
+        p2 = cameraFocalPointForApi
+        q = crosshairPointForApi*/
+
+        /*Vector3 u = p2 - p1;
+        Vector3 pq = q - p1;
+        Vector3 w2 = pq - vtkMath.multiplyScalar(u, vtkMath.dot(pq, u) / u2);
+
+        Vector3 point = q - w2;*/
 
-        const newSliceNormalForApi = [];
-        const newViewUpForApi = [];
+        const cameraFocalPointForApi = cameraForApi.getFocalPoint();
+        const cameraPositionForApi = cameraForApi.getPosition();
 
-        vec3.transformMat4(newSliceNormalForApi, sliceNormalForApi, matrix);
-        vec3.transformMat4(newViewUpForApi, viewUpForApi, matrix);
+        const u = [];
+        vtkMath.subtract(cameraFocalPointForApi, cameraPositionForApi, u);
+        const pq = [];
+        vtkMath.subtract(crosshairPointForApi, cameraPositionForApi, pq);
+        const uLength2 = u[0] * u[0] + u[1] * u[1] + u[2] * u[2];
+        vtkMath.multiplyScalar(u, vtkMath.dot(pq, u) / uLength2);
+        const w2 = [];
+        vtkMath.subtract(pq, u, w2);
+        const point = [];
+        vtkMath.subtract(crosshairPointForApi, w2, point);
 
-        api.setOrientation(newSliceNormalForApi, newViewUpForApi);
+        cameraForApi.setFocalPoint(point[0], point[1], point[2]);
       }
     });
 

src/VTKViewport/vtkSVGRotatableCrosshairsWidget.js

@@ -429,6 +429,9 @@ function vtkSVGRotatableCrosshairsWidget(publicAPI, model) {
     // Set camera focal point to world coordinate for linked views
     apis.forEach((api, apiIndex) => {
       api.set('cachedCrosshairWorldPosition', worldPos);
+      if (api.get('initialCachedCrosshairWorldPosition') === undefined) {
+        api.set('initialCachedCrosshairWorldPosition', worldPos);
+      }
 
       // We are basically doing the same as getSlice but with the world coordinate
       // that we want to jump to instead of the camera focal point.