# projectionCenter does not affect PerspectiveProjection

**URL:** <https://forum.kirupa.com/t/projectioncenter-does-not-affect-perspectiveprojection/302369>\
**Category:** flash\
**Created:** [December 28, 2009, 10:26pm UTC](https://forum.kirupa.com/t/projectioncenter-does-not-affect-perspectiveprojection/302369 "2009-12-28T22:26:17Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Rainman4500](https://avatars.discourse-cdn.com/v4/letter/r/ea5d25/32.png) [@Rainman4500](https://forum.kirupa.com/u/Rainman4500)\
**Post date:** [December 28, 2009, 10:26pm UTC](https://forum.kirupa.com/t/projectioncenter-does-not-affect-perspectiveprojection/302369/1 "2009-12-28T22:26:17Z")

</div>

Complex question for hard core 3D programmers !

I am manually drawing 3D lines on screens. I am NOT using the native X Y Z properties of Sprite.  
private var displayCoordinates:Vector.\<Number\> = new Vector.\<Number\>;  
private var displayMatrix:Matrix3D = new Matrix3D();  
var pp:PerspectiveProjection = new PerspectiveProjection();

```
        pp.projectionCenter = new Point(sizeX/2,sizeY/2);
        displayMatrix = pp.toMatrix3D();

        Utils3D.projectVectors(displayMatrix, worldVertices, displayCoordinates,uvts);

```

// draw on screen based displaycoordinates

No matter what values I put in pp.projectionCenter the Lines always center towards 0,0.

Put another way projectionCenterdoes not change the return value of pp.toMatrix3D()…ever;

I can manually correct this by looping over displayCoordinates and adding the X/2 and Y/2 but seems that I’m missing something important.

Any clues?

Stéphane