diff options
Diffstat (limited to 'helpers.py')
| -rw-r--r-- | helpers.py | 74 |
1 files changed, 41 insertions, 33 deletions
@@ -22,52 +22,58 @@ # By Alex Levenson #================================================================== import math -# distance calculator, pt1 and pt2 are ordred pairs + def distance(pt1, pt2): - return math.sqrt((pt1[0] - pt2[0]) ** 2 + (pt1[1] - pt2[1]) ** 2) + """Distance calculator, pt1 and pt2 are ordred pairs. + """ + return math.sqrt((pt1[0] - pt2[0]) ** 2 + (pt1[1] - pt2[1]) ** 2) -# returns the angle between the line segment from pt1 --> pt2 and the x axis, from -pi to pi def getAngle(pt1, pt2): + """Returns angle between line segment pt1 -> pt2 and x axis, from -pi to pi. + """ xcomp = pt2[0] - pt1[0] ycomp = pt1[1] - pt2[1] return math.atan2(ycomp, xcomp) -# returns a list of ordered pairs that describe an equilteral triangle around the segment from pt1 --> pt2 -def constructTriangleFromLine(p1,p2): +def constructTriangleFromLine(p1, p2): + """Returns list of ordered pairs describing equilteral triangle around segment pt1 --> pt2. + """ halfHeightVector = (0.57735 * (p2[1] - p1[1]), 0.57735 * (p2[0] - p1[0])) p3 = (p1[0] + halfHeightVector[0], p1[1] - halfHeightVector[1]) p4 = (p1[0] - halfHeightVector[0], p1[1] + halfHeightVector[1]) return [p2, p3, p4] -# returns the area of a polygon def polyArea(vertices): + """Returns the area of a polygon. + """ n = len(vertices) A = 0 - p=n - 1 - q=0 + p = n - 1 + q = 0 while q < n: - A+=vertices[p][0] * vertices[q][1] - vertices[q][0] * vertices[p][1] - p=q + A += vertices[p][0] * vertices[q][1] - vertices[q][0] * vertices[p][1] + p = q q += 1 return A / 2.0 -#Some polygon magic, thanks to John W. Ratcliff on www.flipcode.com -# returns true if pt is in triangle def insideTriangle(pt, triangle): - + """Returns true if pt is in triangle. + + Some polygon magic, thanks to John W. Ratcliff on www.flipcode.com + """ ax = triangle[2][0] - triangle[1][0] ay = triangle[2][1] - triangle[1][1] bx = triangle[0][0] - triangle[2][0] by = triangle[0][1] - triangle[2][1] cx = triangle[1][0] - triangle[0][0] cy = triangle[1][1] - triangle[0][1] - apx= pt[0] - triangle[0][0] - apy= pt[1] - triangle[0][1] - bpx= pt[0] - triangle[1][0] - bpy= pt[1] - triangle[1][1] - cpx= pt[0] - triangle[2][0] - cpy= pt[1] - triangle[2][1] + apx = pt[0] - triangle[0][0] + apy = pt[1] - triangle[0][1] + bpx = pt[0] - triangle[1][0] + bpy = pt[1] - triangle[1][1] + cpx = pt[0] - triangle[2][0] + cpy = pt[1] - triangle[2][1] aCROSSbp = ax * bpy - ay * bpx cCROSSap = cx * apy - cy * apx @@ -86,39 +92,42 @@ def polySnip(vertices, u, v, w, n): Cx = vertices[w][0] Cy = vertices[w][1] - if EPSILON > (((Bx-Ax) * (Cy - Ay)) - ((By - Ay) * (Cx - Ax))): return False + if EPSILON > (((Bx-Ax) * (Cy - Ay)) - ((By - Ay) * (Cx - Ax))): + return False for p in range(0, n): - if p == u or p == v or p == w: continue + if p == u or p == v or p == w: + continue Px = vertices[p][0] Py = vertices[p][1] - if insideTriangle((Px, Py), ((Ax, Ay), (Bx, By), (Cx, Cy))): return False + if insideTriangle((Px, Py), ((Ax, Ay), (Bx, By), (Cx, Cy))): + return False return True -# decomposes a polygon into its triangles def decomposePoly(vertices): + """Decomposes a polygon into its triangles. + """ vertices = list(vertices) n = len(vertices) result = [] if(n < 3): return [] # not a poly! - # force a counter-clockwise polygon + # Force counter-clockwise polygon if 0 >= polyArea(vertices): vertices.reverse() - # remove nv-2 vertices, creating 1 triangle every time + # Remove nv-2 vertices, creating 1 triangle every time nv = n count = 2 * nv # error detection - m = 0 v = nv - 1 while nv > 2: count -= 1 if 0 >= count: return [] # Error -- probably bad polygon - # three consecutive vertices + # Three consecutive vertices u = v if nv <= u: u = 0 # previous v = u + 1 @@ -128,18 +137,17 @@ def decomposePoly(vertices): if(polySnip(vertices, u, v, w, nv)): - # record this triangle + # Record this triangle result.append((vertices[u], vertices[v], vertices[w])) - m += 1 - # remove v from remaining polygon + # Remove v from remaining polygon vertices.pop(v) nv -= 1 - # reset error detection + # Reset error detection count = 2 * nv return result -def cast_tuple_to_int(tuple): +def cast_tuple_to_int(tuple_input): """Cast tuple values to ints to avoid gtk+ and pygame's dislike of floats. """ - return [int(i) for i in tuple] + return [int(i) for i in tuple_input] |