Convert a point from world to camera space in Unity3D

Question

I want to convert a point in world coordinates ( P_w ) to camera coordinates ( P_c ).

To do so I first have to translate P_w by the negative camera position (in world coordinates C_pos ) and after that rotate P_w - C_pos x degrees around the x-axis, y degrees around the y-axis and z degrees around the z-axis.

I wrote this function in Unity to do this:

static public Vector4 convertWorldToCameraCoordinatesByDegrees (Vector3 point, PhotoData photoData)
{
    // translate the point by the negative camera-offset 
    //and convert to Vector4
    Vector4 translatedPoint = point - photoData.cameraPosition;
    // by default translatedPoint.w is 0
    translatedPoint.w = 1.0f;       

    // create rotation matrices
    Matrix4x4 rotationMatrixX = Matrix4x4.identity;
    Matrix4x4 rotationMatrixY = Matrix4x4.identity;
    Matrix4x4 rotationMatrixZ = Matrix4x4.identity;

    // setup rotationMatrixX
    rotationMatrixX.SetRow (1, 
        new Vector4 (0,
            Mathf.Cos (photoData.rotation.x),
            - Mathf.Sin (photoData.rotation.x),
            0));
    rotationMatrixX.SetRow (2,
        new Vector4 (0,
            Mathf.Sin (photoData.rotation.x),
            Mathf.Cos (photoData.rotation.x),
            0));

    // setup rotationMatrixY
    rotationMatrixY.SetRow (0, 
        new Vector4 (Mathf.Cos (photoData.rotation.y),
             0,
             Mathf.Sin (photoData.rotation.y),
             0));
    rotationMatrixY.SetRow (2,
        new Vector4 (- Mathf.Sin (photoData.rotation.y),
            0,
            Mathf.Cos (photoData.rotation.y),
            0));                            

    // setup rotationMatrixZ
    rotationMatrixZ.SetRow (0, 
        new Vector4 (Mathf.Cos (photoData.rotation.z),
            - Mathf.Sin (photoData.rotation.z),
            0,
            0));
    rotationMatrixZ.SetRow (1,
        new Vector4 (Mathf.Sin (photoData.rotation.z),
            Mathf.Cos (photoData.rotation.z),
            0,
            0));

    // unity doc says z-x-y in this order
    Matrix4x4 rotationMatrix = rotationMatrixY * rotationMatrixX * rotationMatrixZ;

    Vector4 transformedPoint = rotationMatrix * translatedPoint;

    return transformedPoint;
}

But the results are different from another function where build my roations matrix using the up, forward and right vector of my camera.

PhotoData is a class that has some information about the camera including the position and the rotation. PhotoData.rotation is a Vector3 which has the camera rotation around the x, the y, and the z axis as x-, y-, z-values.

Can someone tell me why this is not working?

// edit: Some people have mentioned build-in functions, but I have to compute this with out them. I forgot to write it in the original post. I wrote this algorithm first in c++ and wanted to test it in Unity since it's easier to verify it.

Answer 1

Looking at your code and think you are massively overcomplicating simple task, or I do not understand the question. You can definitely use Camera.WorldToScreenPoint

http://docs.unity3d.com/ScriptReference/Camera.WorldToScreenPoint.html