SDF Utilities¶

isoext.sdf provides optional utilities for working with signed distance functions. These are convenient for testing and demos, but you can always compute values with your own code.

Note: These utilities are not required — see Working with Grids for examples using raw PyTorch.

import isoext
from isoext.sdf import *
from isoext import viewer

grid = isoext.UniformGrid([128, 128, 128])

Primitives¶

SphereSDF¶

SphereSDF(radius: float)

sphere = SphereSDF(radius=0.7)
grid.set_values(sphere(grid.get_points()))
v, f = isoext.marching_cubes(grid)
viewer.embed(v, f)

TorusSDF¶

TorusSDF(R: float, r: float)  # R=major radius, r=tube radius

torus = TorusSDF(R=0.6, r=0.2)
grid.set_values(torus(grid.get_points()))
v, f = isoext.marching_cubes(grid)
viewer.embed(v, f, color="gold")

CuboidSDF¶

CuboidSDF(size: list[float])  # Full size in [x, y, z]

cube = CuboidSDF(size=[1.0, 1.0, 1.0])
grid.set_values(cube(grid.get_points()))
v, f = isoext.marching_cubes(grid)
viewer.embed(v, f, color="salmon")

CSG Operations¶

Combine shapes using Constructive Solid Geometry:

Operation	Description
`UnionOp([...])`	Combine shapes (min of SDFs)
`IntersectionOp([...])`	Keep overlap (max of SDFs)
`NegationOp(sdf)`	Invert inside/outside
`SmoothUnionOp([...], k)`	Smooth blend with radius k

# Sphere with a hole drilled through it
sphere = SphereSDF(radius=0.7)
hole = CuboidSDF(size=[0.3, 0.3, 2.0])
drilled = IntersectionOp([sphere, NegationOp(hole)])

grid.set_values(drilled(grid.get_points()))
v, f = isoext.marching_cubes(grid)
viewer.embed(v, f, color="orchid")

Transformations¶

Transform	Description
`TranslationOp(sdf, offset)`	Move by `[x, y, z]`
`RotationOp(sdf, axis, angle)`	Rotate around axis (degrees by default)

# Two spheres with smooth blending
s1 = TranslationOp(SphereSDF(radius=0.4), offset=[-0.3, 0, 0])
s2 = TranslationOp(SphereSDF(radius=0.4), offset=[0.3, 0, 0])
blended = SmoothUnionOp([s1, s2], k=0.15)

grid.set_values(blended(grid.get_points()))
v, f = isoext.marching_cubes(grid)
viewer.embed(v, f, color="tomato")