Why do we solve for t here? What can I get after solver for t? I’m confused here.

@bbcd0921 We solve for $t$ because this provides us with many important outputs:

• We know if the ray intersection is valid by checking if $t > 0$.
• We get where the ray hit the surface by plugging $t$ back into the ray equation $r(t) = o + td$.
• We can compare this value of $t$ with other potential intersections to determine which surface the ray hit first.