# MPR slice interaction causes background to expand

**URL:** https://discourse.vtk.org/t/mpr-slice-interaction-causes-background-to-expand/16222
**Category:** Support
**Tags:** code
**Created:** [January 12, 2026, 1:11pm UTC](https://discourse.vtk.org/t/mpr-slice-interaction-causes-background-to-expand/16222 "2026-01-12T13:11:28Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![KSJ](https://discourse.vtk.org/user_avatar/discourse.vtk.org/ksj/32/8659_2.png) [@KSJ](https://discourse.vtk.org/u/KSJ)
#### Post date: [January 12, 2026, 1:11pm UTC](https://discourse.vtk.org/t/mpr-slice-interaction-causes-background-to-expand/16222/1 "2026-01-12T13:11:28Z")

</div>

### **Question**

I am implementing an MPR viewer using VTK (axial / sagittal / coronal) based on the FourPaneViewer / ResliceCursor examples.

My setup includes:

- `vtkResliceImageViewer`

- `vtkResliceCursorWidget`

- `vtkImagePlaneWidget`

- Custom `LeftButtonPressEvent` observer to reposition the reslice cursor

- Parallel projection camera

**Problem:**  
When I move slices (mouse click, scroll, or reslice cursor interaction), the image itself stays centered but the **background expands or shrinks**

I have tried:

- Enabling parallel projection

- Calling `ResetCamera()` only once

- Disabling auto camera clipping (`SetAutoAdjustCameraClippingRange(false)`)

- Restoring `ParallelScale` after slice changes

But the background scaling issue still occurs

![Recording 2026-01-13 104238](https://discourse.vtk.org/uploads/default/original/2X/6/624a4fce63acd534668db20e2aade80e8d666656.gif)