Hello professor. I was just finishing my version of tinyraytracer written in Rust. In

Issues with shadows when rendering duck about tinyraytracer HOT 1 CLOSED

ssloy commented on May 18, 2024

Issues with shadows when rendering duck

from tinyraytracer.

Comments (1)

ema2159 commented on May 18, 2024

Answering my own question, the issue was that I was calculating the intersection between the ray and the planes without considering whether the plane was behind the ray or not. Originally, I was calculating the plane-ray intersection as follows:

        let d = -normal.dot(&self.a.coords); // Parameter of plane equation

        let n_dot_raydir = -normal.dot(&ray.direction);
        if n_dot_raydir <= 0. {
            return None;
        }

        // If it exists, calculate the intersection point
        let t = (normal.dot(&ray.origin.coords) + d) / n_dot_raydir;
        let intersection_point = ray.origin + t * ray.direction;

without taking into consideration the fact that if t is negative, the intersection point is behind the ray, so it should be discarded.
It is sufficient to check for that condition and discard the point accordingly as follows:

        let d = -normal.dot(&self.a.coords); // Parameter of plane equation

        let n_dot_raydir = -normal.dot(&ray.direction);
        if n_dot_raydir <= 0. {
            return None;
        }

        // If it exists, calculate the intersection point
        let t = (normal.dot(&ray.origin.coords) + d) / n_dot_raydir;
        if t < 0. {
            return None;
        } 
        let intersection_point = ray.origin + t * ray.direction;