Ray Base Vector Construction

Parametric Ray Equation:

R(t) = e + (s-e).t

For this we require s and e

e = camera position

s = image plane pixel center

Given:

1. camera position

2. camera view direction

3. Distance between eye and image plane

4. Direction of camera or image plane center

Eye Coordinate System:

In Coding we can built it using following code:

SbVec3f Camera::calculateN(){
 n = direction * (-1);
 n.normalize();
 return n;
}
SbVec3f Camera::calculateU(){
 SbVec3f V = getViewUp();
 SbVec3f normal = calculateN();
 u = V.cross(normal);
 u.normalize();
 return u;
}
SbVec3f Camera::calculateV(){
 v = n.cross(u);
 v.normalize();
 return v;
}

In above code we know the direction in which camera is looking so for calculating n vector we just need to reverse the direction which can be done by multiplying it with -1.

SbVec3f is data type in coin3d which help you to define vectors.

To normalize a vector we have predefined method for vector algebra in C++ normalize()

Next thing we need to construct Image Plane which I explain in my next post