There is an alternative approach in which at at pixel we traverse to display list. In a ray-casting renderer the following process takes place. For each object in the display-list compute the intersection of the given ray Find the closest intersection if there is one Illuminate the point of intersection Many parts of this process should already be somewhat familiar to you. For instance the process of computing the equation of a ray given a screen space coordinate is exactly the inverse of the modeling transform discussed in previous lectures. Actually, it is more straightforward to rederive this expression from first principles using the eye point , the look-at point , and the up vector as before, but the result would be identical.
Lets consider a sphere.
As you know the geometry of a sphere is defined by it center and its radius. The source . The scene file .