feat: add strips on road

src/car.py

@@ -54,6 +54,7 @@ class Car:
 
         if not self.forward and not self.backward:
             self.speed -= sign(self.speed) * self.FRICTION * dt
+            self.speed = max(0, self.speed)
 
         if abs(self.speed) < 1e-4:
             self.speed = 0

src/objects/road.py

@@ -10,9 +10,14 @@ from src.vec import Vec
 class Road(TrackObject):
     type = TrackObjectType.Road
 
+    STRIP_LENGTH = 0.5
+    STRIP_GAP = 0.5
+
     def __init__(self, pts: list[RoadPoint]) -> None:
         super().__init__()
         self.pts: list[RoadPoint] = pts
+        self.strips: list[tuple[Vec, Vec]] = []
+        self.compute_strips()
 
     @classmethod
     def load(cls, data: dict) -> Road:
@@ -40,6 +45,15 @@ class Road(TrackObject):
         pygame.draw.lines(surf, (255, 255, 255), True, side1)
         pygame.draw.lines(surf, (255, 255, 255), True, side2)
 
+        for p1, p2 in self.strips:
+            pygame.draw.line(
+                surf,
+                (255, 255, 255),
+                camera.world2screen(p1),
+                camera.world2screen(p2),
+                6,
+            )
+
     def get_collision_polygons(self) -> list[list[Vec]]:
         side1: list[Vec] = []
         side2: list[Vec] = []
@@ -49,9 +63,50 @@ class Road(TrackObject):
             p3: Vec = p1 - pt.normal * pt.width
             side1.append(p2)
             side2.append(p3)
-
         return [side1, side2]
 
+    def compute_strips(self):
+        n: int = len(self.pts)
+        vecs: list[Vec] = [
+            self.pts[(i + 1) % n].pos - pt.pos for i, pt in enumerate(self.pts)
+        ]
+        lengths: list[float] = [v.mag() for v in vecs]
+        cum_sums: list[float] = [0]
+        for l in lengths:
+            cum_sums.append(cum_sums[-1] + l)
+        self.strips = []
+        total_length: float = sum(lengths)
+
+        def get_pt(length: float) -> tuple[int, float]:
+            length %= total_length
+            for i, cs in list(enumerate(cum_sums))[::-1]:
+                if cs <= length:
+                    return (i, (length - cs) / lengths[i])
+            raise ValueError()
+
+        l0: float = 0
+        while l0 < total_length:
+            l1: float = l0 + self.STRIP_LENGTH
+            i0, t0 = get_pt(l0)
+            i1, t1 = get_pt(l1)
+            p0: Vec = self.pts[i0].pos + vecs[i0] * t0
+            p1: Vec = self.pts[i1].pos + vecs[i1] * t1
+            if i0 == i1:
+                self.strips.append((p0, p1))
+            elif (i0 + 1) % n == i1:
+                pm: Vec = self.pts[i1].pos
+                self.strips.append((p0, pm))
+                self.strips.append((pm, p1))
+            else:
+                self.strips.append((p0, self.pts[(i0 + 1) % n].pos))
+                i = (i0 + 1) % n
+                while i != i1:
+                    i2 = (i + 1) % n
+                    self.strips.append((self.pts[i].pos, self.pts[i2].pos))
+                    i = i2
+                self.strips.append((self.pts[i1].pos, p1))
+            l0 = l1 + self.STRIP_GAP
+
 
 class RoadPoint:
     def __init__(self, pos: Vec, normal: Vec, width: float) -> None: