[Assignment 1] line - sphere intersection: which root should be kept for the quadratic equation ?

[LihengGong]

The text book states:

If the discriminant is positive, there are two solutions: one solution where the ray enters the sphere and one where it leaves.

Question is:

• Which root should be kept?
• How do we know which one is where the ray enters and which one is where the ray leaves?

[hankstag]

yes, if there are two intersection points then you should pick the one that's closer to the camera