# how to change vtkcamera from perspective to parallel gradually

**URL:** https://discourse.vtk.org/t/how-to-change-vtkcamera-from-perspective-to-parallel-gradually/6387
**Category:** Support
**Created:** [August 16, 2021, 12:04pm UTC](https://discourse.vtk.org/t/how-to-change-vtkcamera-from-perspective-to-parallel-gradually/6387 "2021-08-16T12:04:41Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![smoothumut](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/s/9e8a1a/32.png) [@smoothumut](https://discourse.vtk.org/u/smoothumut)
#### Post date: [August 16, 2021, 12:04pm UTC](https://discourse.vtk.org/t/how-to-change-vtkcamera-from-perspective-to-parallel-gradually/6387/1 "2021-08-16T12:04:41Z")

</div>

Hi, I can make the vtkcamera perspective or orthographic by using SetParallelProjection(False/True). But my requirement is to change the view from parallel to perspective or from perspective to parallel GRADUALLY

Here is my requirements  
-The system will display my actor on the screen using perspective camera (done)

-Then user will press a “towards orthographic camera” button (done)

-Then system will decrease the “field of view” or something else by 1 on each click so that camera will display slightly more orthographic view of that actor in each click  
When the variable become 0 then the actor will be displayed fully orthograhic

I am missing something but what, no idea  
I really appreciated for your help, Thanks in advance

---

<div class="post-metadata">

### Author: ![dmreagan](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dmreagan/32/7489_2.png) [@dmreagan](https://discourse.vtk.org/u/dmreagan)
#### Post date: [August 18, 2021, 8:10pm UTC](https://discourse.vtk.org/t/how-to-change-vtkcamera-from-perspective-to-parallel-gradually/6387/2 "2021-08-18T20:10:35Z")

</div>

Try setting the focal distance with `SetDistance()`. As the distance approaches infinity, the projection will approach parallel.