From afa4a696ab06dca87d775ab6d01a2e3674954151 Mon Sep 17 00:00:00 2001
From: PaddleStroke <pierrelouis.boyer@gmail.com>
Date: Mon, 26 Feb 2024 15:56:01 +0100
Subject: [PATCH] Assembly: Fix Object disappears when dragging with slider
 #12449

---
 src/Gui/View3DInventorViewer.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Gui/View3DInventorViewer.cpp b/src/Gui/View3DInventorViewer.cpp
index 671e6ee5b7..9d64f2f240 100644
--- a/src/Gui/View3DInventorViewer.cpp
+++ b/src/Gui/View3DInventorViewer.cpp
@@ -2732,7 +2732,17 @@ SbVec3f View3DInventorViewer::getPointOnLine(const SbVec2s& pnt, const SbVec3f&
     SbVec3f pt, ptOnFocalPlaneAndOnLine, ptOnFocalPlane;
     SbPlane focalPlane = vol.getPlane(focalDist);
     vol.projectPointToLine(pnt2d, line);
-    focalPlane.intersect(line, ptOnFocalPlane);
+
+    if (!focalPlane.intersect(line, ptOnFocalPlane)) {
+        return {};  // No intersection found
+    }
+
+    // Check if line is orthogonal to the focal plane
+    SbVec3f focalPlaneNormal = focalPlane.getNormal();
+    float dotProduct = fabs(axis.dot(focalPlaneNormal));
+    if (dotProduct > 1.0 - 1e-6) {
+        return {};
+    }
 
     SbLine projectedLine = projectLineOntoPlane(axisCenter, axisCenter + axis, focalPlane);
     ptOnFocalPlaneAndOnLine = projectedLine.getClosestPoint(ptOnFocalPlane);