# Off center projection

I'm trying to implement the code that was freely given by a very kind developer at the following link:

Right now, all I'm trying to do is bring it in on one camera, but I have a few issues. My class, looks as follows:

``````using UnityEngine;
using System.Collections;

public class PerspectiveOffCenter : MonoBehaviour
{

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {

}

public static Matrix4x4 GeneralizedPerspectiveProjection(Vector3 pa, Vector3 pb, Vector3 pc, Vector3 pe, float near, float far)
{
Vector3 va, vb, vc;
Vector3 vr, vu, vn;

float left, right, bottom, top, eyedistance;

Matrix4x4 transformMatrix;
Matrix4x4 projectionM;
Matrix4x4 eyeTranslateM;
Matrix4x4 finalProjection;

///Calculate the orthonormal for the screen (the screen coordinate system
vr = pb - pa;
vr.Normalize();
vu = pc - pa;
vu.Normalize();
vn = Vector3.Cross(vr, vu);
vn.Normalize();

//Calculate the vector from eye (pe) to screen corners (pa, pb, pc)
va = pa-pe;
vb = pb-pe;
vc = pc-pe;

//Get the distance;; from the eye to the screen plane
eyedistance = -(Vector3.Dot(va, vn));

//Get the varaibles for the off center projection
left    = (Vector3.Dot(vr, va)*near)/eyedistance;
right   = (Vector3.Dot(vr, vb)*near)/eyedistance;
bottom  = (Vector3.Dot(vu, va)*near)/eyedistance;
top     = (Vector3.Dot(vu, vc)*near)/eyedistance;

//Get this projection
projectionM = PerspectiveOffCenter(left, right, bottom, top, near, far);

//Fill in the transform matrix
transformMatrix = new Matrix4x4();

transformMatrix[0, 0] = vr.x;
transformMatrix[0, 1] = vr.y;
transformMatrix[0, 2] = vr.z;
transformMatrix[0, 3] = 0;

transformMatrix[1, 0] = vu.x;
transformMatrix[1, 1] = vu.y;
transformMatrix[1, 2] = vu.z;
transformMatrix[1, 3] = 0;

transformMatrix[2, 0] = vn.x;
transformMatrix[2, 1] = vn.y;
transformMatrix[2, 2] = vn.z;
transformMatrix[2, 3] = 0;

transformMatrix[3, 0] = 0;
transformMatrix[3, 1] = 0;
transformMatrix[3, 2] = 0;
transformMatrix[3, 3] = 1;

//Now for the eye transform
eyeTranslateM = new Matrix4x4();

eyeTranslateM[0, 0] = 1;
eyeTranslateM[0, 1] = 0;
eyeTranslateM[0, 2] = 0;
eyeTranslateM[0, 3] = -pe.x;

eyeTranslateM[1, 0] = 0;
eyeTranslateM[1, 1] = 1;
eyeTranslateM[1, 2] = 0;
eyeTranslateM[1, 3] = -pe.y;

eyeTranslateM[2, 0] = 0;
eyeTranslateM[2, 1] = 0;
eyeTranslateM[2, 2] = 1;
eyeTranslateM[2, 3] = -pe.z;

eyeTranslateM[3, 0] = 0;
eyeTranslateM[3, 1] = 0;
eyeTranslateM[3, 2] = 0;
eyeTranslateM[3, 3] = 1f;

//Multiply all together
finalProjection = new Matrix4x4();
finalProjection = Matrix4x4.identity * projectionM*transformMatrix*eyeTranslateM;

//finally return
return finalProjection;
}

// Update is called once per frame

public void FixedUpdate ()
{
Camera cam = camera;

//calculate projection
Matrix4x4 genProjection = GeneralizedPerspectiveProjection( new Vector3(0,1,0), new Vector3(1,1,0), new Vector3(0,0,0), new Vector3(0,0,0), cam.nearClipPlane, cam.farClipPlane);
//(BottomLeftCorner, BottomRightCorner, TopLeftCorner, trackerPosition, cam.nearClipPlane, cam.farClipPlane);
cam.projectionMatrix = genProjection;

}
}
``````

My error lies in `projectionM = PerspectiveOffCenter(left, right, bottom, top, near, far);`

The debugger states:

Expression denotes a `type', where a 'variable', 'value' or 'method group' was expected.

Thus, I changed the line to read: `projectionM = new PerspectiveOffCenter(left, right, bottom, top, near, far);`

But then the error is changed to:

The type 'PerspectiveOffCenter' does not contain a constructor that takes '6' arguments.

For reasons that are obvious.

So, finally, I changed the line to read: `projectionM = new GeneralizedPerspectiveProjection(left, right, bottom, top, near, far);`

And the error I get is:

is a 'method' but a 'type' was expected.

With this last error, I'm not sure what it is I should do / missing. Can anyone see what it is that I'm missing to fix this error?

-

You're trying to complete the method `GeneralizedPerspectiveProjection()` I'm pretty sure trying to use `GeneralizedPerspectiveProjection()` within that method is a poor choice. I dodn't see anything to indicate that this was a recursive method.

``````public class PerspectiveOffCenter : MonoBehaviour
Your class is named `PerspectiveOffCenter`. Then when you're trying to run the code you pasted in you're getting the following error: