diff options
| -rw-r--r-- | src/main.zig | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/src/main.zig b/src/main.zig index c862e1e..a60526a 100644 --- a/src/main.zig +++ b/src/main.zig @@ -84,22 +84,34 @@ const Ray = struct { } }; -fn hitSphere(center: Point3, radius: f64, r: Ray) bool { +fn hitSphere(center: Point3, radius: f64, r: Ray) f64 { const oc = r.origin.sub(center); const a = Vec3.dot(r.dir, r.dir); const b = 2.0 * Vec3.dot(oc, r.dir); const c = Vec3.dot(oc, oc) - radius * radius; const discriminant = b * b - 4.0 * a * c; - return discriminant > 0.0; + if (discriminant < 0.0) { + // r does not intersect the sphere. + return -1.0; + } else { + // root of the equation. + return (-b - @sqrt(discriminant)) / (2.0 * a); + } } fn rayColor(r: Ray) Color { - if (hitSphere(Point3{ .x = 0.0, .y = 0.0, .z = -1.0 }, 0.5, r)) { - return Color{ .x = 1.0, .y = 0.0, .z = 0.0 }; + const sphereOrigin = Point3{ .x = 0.0, .y = 0.0, .z = -1.0 }; + const sphereRadius = 0.5; + + const t = hitSphere(sphereOrigin, sphereRadius, r); + if (t > 0.0) { + // r hints the sphere. + const sphereNormal = r.at(t).sub(sphereOrigin).normalized(); + return (Color{ .x = sphereNormal.x + 1.0, .y = sphereNormal.y + 1.0, .z = sphereNormal.z + 1.0 }).mul(0.5); } const unit_dir = r.dir.normalized(); - const t = 0.5 * (unit_dir.y + 1.0); - return (Color{ .x = 1.0, .y = 1.0, .z = 1.0 }).mul(1.0 - t).add((Color{ .x = 0.5, .y = 0.7, .z = 1.0 }).mul(t)); + const s = 0.5 * (unit_dir.y + 1.0); + return (Color{ .x = 1.0, .y = 1.0, .z = 1.0 }).mul(1.0 - s).add((Color{ .x = 0.5, .y = 0.7, .z = 1.0 }).mul(s)); } fn writeColor(out: anytype, c: Color) !void { |