Added Ray type

src/ray.nim

@@ -0,0 +1,34 @@
+from "./tuple" import Tuple4, isPoint, isVector, `+`, `*`
+
+type
+    Ray* = object
+        origin: Tuple4
+        direction: Tuple4
+    RayCreationError = object of CatchableError
+
+proc ray(origin, direction: Tuple4): Ray =
+    if(not origin.isPoint() or not direction.isVector()):
+        raise newException(RayCreationError, "origin must be a point and direction must be a vector")
+    result.origin = origin
+    result.direction = direction
+
+proc position(ray: Ray, t: float): Tuple4 =
+    ray.origin + ray.direction * t
+
+when isMainModule:
+    import unittest
+    from "./tuple" import point, vector, `==`
+    suite "ray":
+        test "Ray creation":
+            let origin = point(1.0, 2.0, 3.0)
+            let direction = vector(4.0, 5.0, 6.0)
+            let ray = ray(origin, direction)
+            check(ray.origin == origin)
+            check(ray.direction == direction)
+
+        test "Computing a point from a distance":
+            let ray = ray(point(2.0, 3.0, 4.0), vector(1.0, 0.0, 0.0))
+            check(ray.position(0.0) == point(2.0, 3.0, 4.0))
+            check(ray.position(1.0) == point(3.0, 3.0, 4.0))
+            check(ray.position(-1.0) == point(1.0, 3.0, 4.0))
+            check(ray.position(2.5) == point(4.5, 3.0, 4.0))