# isosurfacesforp3d / src / tetrahedrons.py

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228``` ```class Vector: # struct XYZ def __init__(self, x, y, z): self.x = x self.y = y self.z = z def __str__(self): return str(self.x) + " " + str(self.y) + " " + str(self.z) class Gridcell: # struct GRIDCELL def __init__(self, p, n, val): self.p = p # p=[8] self.n = n # n=[8] self.val = val # val=[8] class Triangle: # struct TRIANGLE def __init__(self, p1, p2, p3): self.p = [p1, p2, p3] # vertices def flip(self): self.p.reverse() # return triangle as an ascii STL facet def __str__(self): return ("facet normal 0 0 0\nouter loop\nvertex %s\nvertex %s\nvertex %s\nendloop\nendfacet" % (self.p[0], self.p[1], self.p[2])) # return a 3d list of values def readdata(f=lambda x, y, z: x * x + y * y + z * z, size=5.0, steps=11): m = int(steps / 2) ki = [] for i in range(steps): kj = [] for j in range(steps): kd = [] for k in range(steps): kd.append(f(size * (i - m) / m, size * (j - m) / m, size * (k - m) / m)) kj.append(kd) ki.append(kj) return ki from math import cos, exp, atan2 def lobes(x, y, z): try: theta = atan2(x, y) # sin t = o except: theta = 0 try: phi = atan2(z, y) except: phi = 0 r = x * x + y * y + z * z ct = cos(theta) cp = cos(phi) return ct * ct * cp * cp * exp(-r / 10) def main(): data = readdata(lobes, 5, 41) isolevel = 0.1 dr = lambda x, y, z:data[x][y][z] xmin = 0 xmax = len(data) - 1 ymin = 0 ymax = len(data[0]) - 1 zmin = 0 zmax = len(data[0][0]) - 1 #print(data) export(dr, isolevel, xmin, xmax, ymin, ymax, zmin, zmax) def export(density_function, isolevel, xmin, xmax, ymin, ymax, zmin, zmax): triangles = [] p = [None] * 8 val = [None] * 8 for i in range(xmin, xmax): for j in range(ymin, ymax): for k in range(zmin, zmax): #print(i,j,k) p[0] = Vector(i, j, k) val[0] = density_function(i, j, k) p[1] = Vector(i + 1, j, k) val[1] = density_function(i + 1, j, k) p[2] = Vector(i + 1, j + 1, k) val[2] = density_function(i + 1, j + 1, k) p[3] = Vector(i, j + 1, k) val[3] = density_function(i, j + 1, k) p[4] = Vector(i, j, k + 1) val[4] = density_function(i, j, k + 1) p[5] = Vector(i + 1, j, k + 1) val[5] = density_function(i + 1, j, k + 1) p[6] = Vector(i + 1, j + 1, k + 1) val[6] = density_function(i + 1, j + 1, k + 1) p[7] = Vector(i, j + 1, k + 1) val[7] = density_function(i, j + 1, k + 1) grid = Gridcell(p, [], val) triangles.extend(PolygoniseTri(grid, isolevel, 0, 2, 3, 7)) triangles.extend(PolygoniseTri(grid, isolevel, 0, 2, 6, 7)) triangles.extend(PolygoniseTri(grid, isolevel, 0, 4, 6, 7)) triangles.extend(PolygoniseTri(grid, isolevel, 0, 6, 1, 2)) triangles.extend(PolygoniseTri(grid, isolevel, 0, 6, 1, 4)) triangles.extend(PolygoniseTri(grid, isolevel, 5, 6, 1, 4)) export_triangles(triangles) def export_triangles(triangles): # stl format print("solid points") for tri in triangles: print(tri) print("endsolid points") def t000F(g, iso, v0, v1, v2, v3): return [] def t0E01(g, iso, v0, v1, v2, v3): return [Triangle( VertexInterp(iso, g.p[v0], g.p[v1], g.val[v0], g.val[v1]), VertexInterp(iso, g.p[v0], g.p[v2], g.val[v0], g.val[v2]), VertexInterp(iso, g.p[v0], g.p[v3], g.val[v0], g.val[v3])) ] def t0D02(g, iso, v0, v1, v2, v3): return [Triangle( VertexInterp(iso, g.p[v1], g.p[v0], g.val[v1], g.val[v0]), VertexInterp(iso, g.p[v1], g.p[v3], g.val[v1], g.val[v3]), VertexInterp(iso, g.p[v1], g.p[v2], g.val[v1], g.val[v2])) ] def t0C03(g, iso, v0, v1, v2, v3): tri = Triangle( VertexInterp(iso, g.p[v0], g.p[v3], g.val[v0], g.val[v3]), VertexInterp(iso, g.p[v0], g.p[v2], g.val[v0], g.val[v2]), VertexInterp(iso, g.p[v1], g.p[v3], g.val[v1], g.val[v3])) return [tri, Triangle( tri.p[2], VertexInterp(iso, g.p[v1], g.p[v2], g.val[v1], g.val[v2]), tri.p[1]) ] def t0B04(g, iso, v0, v1, v2, v3): return [Triangle( VertexInterp(iso, g.p[v2], g.p[v0], g.val[v2], g.val[v0]), VertexInterp(iso, g.p[v2], g.p[v1], g.val[v2], g.val[v1]), VertexInterp(iso, g.p[v2], g.p[v3], g.val[v2], g.val[v3])) ] def t0A05(g, iso, v0, v1, v2, v3): tri = Triangle( VertexInterp(iso, g.p[v0], g.p[v1], g.val[v0], g.val[v1]), VertexInterp(iso, g.p[v2], g.p[v3], g.val[v2], g.val[v3]), VertexInterp(iso, g.p[v0], g.p[v3], g.val[v0], g.val[v3])) return [tri, Triangle( tri.p[0], VertexInterp(iso, g.p[v1], g.p[v2], g.val[v1], g.val[v2]), tri.p[1]) ] def t0906(g, iso, v0, v1, v2, v3): tri = Triangle( VertexInterp(iso, g.p[v0], g.p[v1], g.val[v0], g.val[v1]), VertexInterp(iso, g.p[v1], g.p[v3], g.val[v1], g.val[v3]), VertexInterp(iso, g.p[v2], g.p[v3], g.val[v2], g.val[v3])) return [tri, Triangle( tri.p[0], VertexInterp(iso, g.p[v0], g.p[v2], g.val[v0], g.val[v2]), tri.p[2]) ] def t0708(g, iso, v0, v1, v2, v3): return [Triangle( VertexInterp(iso, g.p[v3], g.p[v0], g.val[v3], g.val[v0]), VertexInterp(iso, g.p[v3], g.p[v2], g.val[v3], g.val[v2]), VertexInterp(iso, g.p[v3], g.p[v1], g.val[v3], g.val[v1])) ] trianglefs_dict = {7:t0708, 8:t0708, 9:t0906, 6:t0906, 10:t0A05, 5:t0A05, 11:t0B04, 4:t0B04, 12:t0C03, 3:t0C03, 13:t0D02, 2:t0D02, 14:t0E01, 1:t0E01, 0:t000F, 15:t000F} trianglefs = list(trianglefs_dict[i] for i in range(16)) def PolygoniseTri(g, iso, v0, v1, v2, v3): triangles = [] # Determine which of the 16 cases we have given which vertices # are above or below the isosurface triindex = 0 if g.val[v0] < iso: triindex |= 1 if g.val[v1] < iso: triindex |= 2 if g.val[v2] < iso: triindex |= 4 if g.val[v3] < iso: triindex |= 8 l = trianglefs[triindex](g, iso, v0, v1, v2, v3) if triindex == 7 or (triindex != 8 and triindex & 8): for tri in l: tri.flip() return l def VertexInterp(isolevel, p1, p2, valp1, valp2): if abs(isolevel - valp1) < 0.00001: return(p1) if abs(isolevel - valp2) < 0.00001: return(p2) if abs(valp1 - valp2) < 0.00001: return(p1) mu = (isolevel - valp1) / (valp2 - valp1) return Vector(p1.x + mu * (p2.x - p1.x), p1.y + mu * (p2.y - p1.y), p1.z + mu * (p2.z - p1.z)) if __name__ == "__main__": main() ```