Signed Distance Functions #61
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Add a `__hash__()` function and create missing bits of the context to allow for easy VM execution.
This allows creating meshes in new ways. Implementation is built on the existing `Model()` class hierarchy with a new `signed_distance()` method.
The positive outside convention is just more common in examples found online and so I think probably less confusing.
Picks 1/100th of the largest axis range.
Cython seems to be generating bad code with them being cpdef.
Also, ensure that we don't push a `!trim` through another CSG operation if either the `!trim` or the other operation involve boundary effects.
This is *very, very* slow and requires the `rtree` package be installed.
jonathanhogg
added
🚀 enhancement
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This PR adds support for generating meshes from signed distance functions (/fields). It adds a new
!sdfmodel node that takes either afunction=attribute or a set of sub-nodes.The
function=attribute takes an actual Flitter function taking a 3-vector position (in the model coordinate system) and returning a signed distance (with the positive is outside convention).If a set of sub-nodes is given instead then these are evaluated in the same way that a CSG model hierarchy is evaluated except all of the operations and primitives are SDFs. This hierarchy may contain
!sdfnodes specifying custom functions.The
!trim,!union,!intersectand!differencenodes are extended to have newsmooth=,fillet=andchamfer=attributes that allow for various boundary effects. These only work in an SDF hierarchy and are ignored for normal mesh CSG operations.The top level
!sdfnode should also be supplied withminimum=andmaximum=attributes taking 3-vectors of the model-coordinate bounds to evaluate the SDF over, and aresolution=attribute giving the density to evaluate the function over as a length in the model coordinate system – smaller values require greater computation.maximumdefaults to1andminimumdefaults to negativemaximum.