Line collidepolygon() and Polygon collideline()

docs/geometry.rst

@@ -126,6 +126,8 @@ other objects.
 
     colliderect: Checks if the line collides with the given rectangle.
 
+    collidepolygon: Checks if the line collides with the given polygon.
+
     collideswith: Checks if the line collides with the given object.
 
     as_circle: Returns a circle which fully encloses the line.
@@ -174,6 +176,8 @@ other objects.
 
     collidepoint: Checks if the polygon collides with the given point.
 
+    collideline: Checks if the polygon collides with the given line.
+
     collidecircle: Checks if the polygon collides with the given circle.
 
     insert_vertex: Adds a vertex to the polygon.

docs/line.rst

@@ -320,6 +320,29 @@ Line Methods
 
       .. ## Line.collidecircle ##
 
+    .. method:: collidepolygon
+
+        | :sl:`test if a line intersects with a polygon`
+        | :sg:`collidepolygon(Polygon, only_edges=False) -> bool`
+        | :sg:`collidepolygon((x1, y1), (x2, y2), ..., only_edges=False) -> bool`
+        | :sg:`collidepolygon(x1, y1, x2, y2, ..., only_edges=False) -> bool`
+
+        Tests whether a given `Polygon` collides with the `Line`.
+        It takes either a `Polygon` or Polygon-like object as an argument and it returns
+        `True` if the polygon collides with the `Line`, `False` otherwise.
+
+        The optional `only_edges` argument can be set to `True` to only test whether the
+        edges of the polygon intersect the `Line`. This means that a Line that is
+        inscribed by the `Polygon` or completely outside of it will not be considered colliding.
+        This can be useful for performance reasons if you only care about the edges of the
+        polygon.
+
+        .. note::
+            Keep in mind that the more vertices the polygon has, the more CPU time it will
+            take to calculate the collision.
+
+      .. ## Line.collidepolygon ##
+
 
     .. method:: collideswith
 

docs/polygon.rst

@@ -157,6 +157,23 @@ Polygon Methods
 
       .. ## Polygon.collidepoint ##
 
+    .. method:: collideline
+
+        | :sl:`tests if a line intersects the polygon`
+        | :sg:`collideline(Line, only_edges=False) -> bool`
+        | :sg:`collideline((x1, y1), (x2, y2), only_edges=False) -> bool`
+        | :sg:`collideline(x1, y1, x2, y2, only_edges=False) -> bool`
+
+        Tests whether a given `Line` collides with the `Polygon`.
+        It takes either a `Line` or Line-like object as an argument and it returns `True`
+        if the `Line` collides with the `Polygon`, `False` otherwise.
+
+        The optional `only_edges` argument can be set to `True` to only test whether the
+        edges of the polygon intersect the `Line`. This means that a Line that is
+        inscribed by the `Polygon` or completely outside of it will not be considered colliding.
+
+      .. ## Polygon.collideline ##  
+
     .. method:: collidecircle
 
         | :sl:`tests if a circle is inside the polygon`
@@ -171,6 +188,7 @@ Polygon Methods
         The optional `only_edges` argument can be set to `True` to only test whether the
         edges of the polygon intersect the `Circle`. This means that a Polygon that is
         completely inscribed in, or circumscribed by the `Circle` will not be considered colliding.
+
         This can be useful for performance reasons if you only care about the edges of the
         polygon.
 

examples/polygon_line_collision.py

@@ -0,0 +1,108 @@
+from math import radians, sin, cos
+
+import pygame
+from pygame.draw import line as draw_line, polygon as draw_polygon
+from geometry import Line, regular_polygon
+
+
+# using this because we're missing line.rotate(), rotates a line around its midpoint
+def rotate_line(line, d_ang):
+    angle = radians(d_ang)
+    ca, sa = cos(angle), sin(angle)
+    xm, ym = line.midpoint
+    ax, ay = line.a
+    bx, by = line.b
+    ax -= xm
+    ay -= ym
+    bx -= xm
+    by -= ym
+    new_ax, new_ay = xm + ax * ca - ay * sa, ym + ax * sa + ay * ca
+    new_bx, new_by = xm + bx * ca - by * sa, ym + bx * sa + by * ca
+    line.a, line.b = (new_ax, new_ay), (new_bx, new_by)
+
+
+pygame.init()
+
+WHITE = (255, 255, 255)
+YELLOW = (255, 255, 0)
+RED = (255, 0, 0)
+SHAPE_THICKNESS = 3
+FPS = 60
+WIDTH, HEIGHT = 800, 800
+WIDTH2, HEIGHT2 = WIDTH // 2, HEIGHT // 2
+
+screen = pygame.display.set_mode((WIDTH, HEIGHT))
+pygame.display.set_caption("Polygon-Line Collision Visualization")
+clock = pygame.time.Clock()
+
+font = pygame.font.SysFont("Arial", 25, bold=True)
+colliding_text = font.render("Colliding", True, RED)
+colliding_textr = colliding_text.get_rect(center=(WIDTH2, 50))
+not_colliding_text = font.render("Not colliding", True, WHITE)
+not_colliding_textr = not_colliding_text.get_rect(center=(WIDTH2, 50))
+
+modei_text = font.render("Right click to toggle collision mode", True, WHITE)
+modei_textr = modei_text.get_rect(center=(WIDTH2, HEIGHT - 50))
+
+modei2_text = font.render("Left click to rotate", True, WHITE)
+modei2_textr = modei2_text.get_rect(center=(WIDTH2, HEIGHT - 80))
+
+mode0_txt = font.render("Current: EDGES ONLY", True, YELLOW)
+mode0_txtr = mode0_txt.get_rect(center=(WIDTH2, HEIGHT - 25))
+
+mode1_txt = font.render("Current: FULL", True, YELLOW)
+mode1_txtr = mode1_txt.get_rect(center=(WIDTH2, HEIGHT - 25))
+
+polygon = regular_polygon(6, (WIDTH2, HEIGHT2), 180)
+line = Line((0, 0), (135, 135))
+only_edges = False
+running = True
+color = WHITE
+
+rotating = False
+
+while running:
+    delta = (clock.tick(FPS) / 1000) * 60
+
+    line.midpoint = pygame.mouse.get_pos()
+
+    colliding = line.collidepolygon(polygon, only_edges)
+    # Alternative:
+    # colliding = polygon.collideline(line, only_edges)
+
+    if rotating:
+        rotate_line(line, 2)
+
+    color = RED if colliding else WHITE
+
+    screen.fill((10, 10, 10))
+
+    draw_polygon(screen, color, polygon.vertices, SHAPE_THICKNESS)
+    draw_line(screen, color, line.a, line.b, SHAPE_THICKNESS)
+
+    screen.blit(
+        colliding_text if colliding else not_colliding_text,
+        colliding_textr if colliding else not_colliding_textr,
+    )
+
+    screen.blit(modei2_text, modei2_textr)
+    screen.blit(modei_text, modei_textr)
+
+    screen.blit(
+        mode0_txt if only_edges else mode1_txt, mode0_txtr if only_edges else mode1_txtr
+    )
+
+    pygame.display.flip()
+
+    for event in pygame.event.get():
+        if event.type == pygame.QUIT:
+            running = False
+        elif event.type == pygame.MOUSEBUTTONDOWN:
+            if event.button == 1:
+                rotating = True
+            elif event.button == 3:
+                only_edges = not only_edges
+        elif event.type == pygame.MOUSEBUTTONUP:
+            if event.button == 1:
+                rotating = False
+pygame.quit()

geometry.pyi

@@ -111,6 +111,7 @@ class Line(Sequence[float]):
     def collidecircle(self, circle: CircleValue) -> bool: ...
     @overload
     def collidecircle(self, x: float, y: float, r: float) -> bool: ...
+    def collidepolygon(self, polygon: Polygon, only_edges: bool = False) -> bool: ...
     def as_circle(self) -> Circle: ...
     def as_rect(self) -> Rect: ...
     @overload
@@ -243,6 +244,7 @@ class Polygon:
     def collidepoint(self, x: float, y: float) -> bool: ...
     @overload
     def collidepoint(self, point: Coordinate) -> bool: ...
+    def collideline(self, line: LineValue, only_edges: bool = False) -> bool: ...
     def get_bounding_box(self) -> Rect: ...
     def is_convex(self) -> bool: ...
     @overload

src_c/collisions.c

@@ -321,6 +321,68 @@ pgCollision_PolygonPoint(pgPolygonBase *poly, double x, double y)
     return collision;
 }
 
+static inline int
+pgCollision_PolygonPoints(pgPolygonBase *poly, double x1, double y1, double x2,
+                          double y2)
+{
+    int collision1 = 0, collision2 = 0;
+    Py_ssize_t i, j;
+
+    double *vertices = poly->vertices;
+
+    for (i = 0, j = poly->verts_num - 1; i < poly->verts_num; j = i++) {
+        double xi = vertices[i * 2];
+        double yi = vertices[i * 2 + 1];
+        double xj = vertices[j * 2];
+        double yj = vertices[j * 2 + 1];
+
+        double xj_xi = xj - xi;
+        double yj_yi = yj - yi;
+
+        if (((yi > y1) != (yj > y1)) &&
+            (x1 < xj_xi * (y1 - yi) / yj_yi + xi)) {
+            collision1 = !collision1;
+        }
+
+        if (((yi > y2) != (yj > y2)) &&
+            (x2 < xj_xi * (y2 - yi) / yj_yi + xi)) {
+            collision2 = !collision2;
+        }
+    }
+
+    return collision1 || collision2;
+}
+
+static inline int
+_pgCollision_line_polyedges(pgLineBase *line, pgPolygonBase *poly)
+{
+    Py_ssize_t i, j;
+    double *vertices = poly->vertices;
+
+    for (i = 0, j = poly->verts_num - 1; i < poly->verts_num; j = i++) {
+        if (pgCollision_LineLine(
+                line, &(pgLineBase){vertices[j * 2], vertices[j * 2 + 1],
+                                    vertices[i * 2], vertices[i * 2 + 1]})) {
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+static inline int
+pgCollision_PolygonLine(pgPolygonBase *poly, pgLineBase *line, int only_edges)
+{
+    int collision = _pgCollision_line_polyedges(line, poly);
+
+    if (collision || only_edges) {
+        return collision;
+    }
+
+    return pgCollision_PolygonPoints(poly, line->x1, line->y1, line->x2,
+                                     line->y2);
+}
+
 static int
 _pgCollision_PolygonPoint_opt(pgPolygonBase *poly, double x, double y)
 {

src_c/include/collisions.h

@@ -43,7 +43,10 @@ pgRaycast_LineCircle(pgLineBase *, pgCircleBase *, double, double *);
 static int
 pgCollision_PolygonPoint(pgPolygonBase *, double, double);
 
+static int
+pgCollision_PolygonLine(pgPolygonBase *, pgLineBase *, int);
 static int
 pgCollision_CirclePolygon(pgCircleBase *, pgPolygonBase *, int);
 
+
 #endif /* ~_PG_COLLISIONS_H */

src_c/line.c

@@ -116,7 +116,7 @@ pgLine_FromObject(PyObject *obj, pgLineBase *out)
     }
     if (PySequence_Check(obj)) {
         length = PySequence_Length(obj);
-        if (length == 4) {
+        if (length == 4 && !pgPolygon_Check(obj)) {
             PyObject *tmp;
             tmp = PySequence_GetItem(obj, 0);
             if (!pg_DoubleFromObj(tmp, &(out->x1))) {
@@ -169,6 +169,9 @@ pgLine_FromObject(PyObject *obj, pgLineBase *out)
             Py_DECREF(sub);
             return IS_LINE_VALID(out);
         }
+        else {
+            return 0;
+        }
     }
     if (PyObject_HasAttrString(obj, "line")) {
         PyObject *lineattr;
@@ -692,6 +695,32 @@ pg_line_scale_ip(pgLineObject *self, PyObject *const *args, Py_ssize_t nargs) {
     Py_RETURN_NONE;
 }
 
+static PyObject *
+pg_line_collidepolygon(pgLineObject *self, PyObject *const *args,
+                       Py_ssize_t nargs)
+{
+    pgPolygonBase poly;
+    int was_sequence, result, only_edges = 0;
+
+    /* Check for the optional only_edges argument */
+    if (PyBool_Check(args[nargs - 1])) {
+        only_edges = args[nargs - 1] == Py_True;
+        nargs--;
+    }
+
+    if (!pgPolygon_FromObjectFastcall(args, nargs, &poly, &was_sequence)) {
+        return RAISE(
+            PyExc_TypeError,
+            "collidepolygon requires a Polygon or PolygonLike object");
+    }
+
+    result = pgCollision_PolygonLine(&poly, &self->line, only_edges);
+
+    PG_FREEPOLY_COND(&poly, was_sequence);
+
+    return PyBool_FromLong(result);
+}
+
 static PyObject *
 pg_line_as_circle(pgLineObject *self, PyObject *_null)
 {
@@ -718,6 +747,8 @@ static struct PyMethodDef pg_line_methods[] = {
     {"collidecircle", (PyCFunction)pg_line_collidecircle, METH_FASTCALL, NULL},
     {"colliderect", (PyCFunction)pg_line_colliderect, METH_FASTCALL, NULL},
     {"collideswith", (PyCFunction)pg_line_collideswith, METH_O, NULL},
+    {"collidepolygon", (PyCFunction)pg_line_collidepolygon, METH_FASTCALL,
+     NULL},
     {"as_rect", (PyCFunction)pg_line_as_rect, METH_NOARGS, NULL},
     {"update", (PyCFunction)pg_line_update, METH_FASTCALL, NULL},
     {"move", (PyCFunction)pg_line_move, METH_FASTCALL, NULL},

src_c/polygon.c

@@ -1190,7 +1190,6 @@ pg_polygon_is_convex(pgPolygonObject *self, PyObject *_null)
 {
     return PyBool_FromLong(_pg_polygon_is_convex_helper(&self->polygon));
 }
-
 static int
 _pg_polygon_scale_helper(pgPolygonBase *poly, double factor)
 {
@@ -1258,6 +1257,27 @@ pg_polygon_scale_ip(pgPolygonObject *self, PyObject *arg)
     Py_RETURN_NONE;
 }
 
+static PyObject *
+pg_polygon_collideline(pgPolygonObject *self, PyObject *const *args,
+                       Py_ssize_t nargs)
+{
+    pgLineBase line;
+    int only_edges = 0;
+
+    /* Check for the optional only_edges argument */
+    if (PyBool_Check(args[nargs - 1])) {
+        only_edges = args[nargs - 1] == Py_True;
+        nargs--;
+    }
+
+    if (!pgLine_FromObjectFastcall(args, nargs, &line)) {
+        return RAISE(PyExc_TypeError, "Invalid line parameter");
+    }
+
+    return PyBool_FromLong(
+        pgCollision_PolygonLine(&self->polygon, &line, only_edges));
+}
+
 static PyObject *
 pg_polygon_collidecircle(pgPolygonObject *self, PyObject *const *args,
                          Py_ssize_t nargs)
@@ -1287,6 +1307,7 @@ static struct PyMethodDef pg_polygon_methods[] = {
     {"rotate_ip", (PyCFunction)pg_polygon_rotate_ip, METH_FASTCALL, NULL},
     {"collidepoint", (PyCFunction)pg_polygon_collidepoint, METH_FASTCALL,
      NULL},
+    {"collideline", (PyCFunction)pg_polygon_collideline, METH_FASTCALL, NULL},
     {"collidecircle", (PyCFunction)pg_polygon_collidecircle, METH_FASTCALL,
      NULL},
     {"get_bounding_box", (PyCFunction)pg_polygon_get_bounding_box, METH_NOARGS,