Offset Support Volume Generated with STL File.

[Vipul-M-Rawal]

When generating the support volume for an STL file using PySLM, the resulting support volume appears to be offset from the expected position. This misalignment makes the generated support geometry unusable for further operations like slicing or additive manufacturing.

Expected Behavior
The support volume should align perfectly with the base STL geometry.

Actual Behavior
The generated support volume is offset relative to the input STL file.

Parameters I am using:

supportGenerator.innerSupportEdgeGap = 0.3 # [mm] - Inner support offset used between adjacent support distances
supportGenerator.outerSupportEdgeGap = 2.0 # [mm] - Outer support offset used for the boundaries of overhang regions
supportGenerator.simplifyPolygonFactor = 0.5 # - Factor used for simplifying the overall support shape
supportGenerator.triangulationSpacing = 2.0 # [mm] - Used for triangulating the extruded polygon for the bloc
supportGenerator.minimumAreaThreshold = 0.2 # Minimum area threshold to not process support region'
supportGenerator.triangulationSpacing = 4 # [mm^2] - Internal parameter used for generating the mesh of the volume
supportGenerator.supportBorderDistance = 1.0 # [mm]
supportGenerator.numSkinMeshSubdivideIterations = 2

Support teeth parameters

supportGenerator.useUpperSupportTeeth = True
supportGenerator.useLowerSupportTeeth = True
supportGenerator.supportWallThickness = 1.0 # [mm] - The thickness of the upper and support walls to strengthen teeth regions
supportGenerator.supportTeethTopLength = 0.1 # [mm] - The length of the tab for the support teeth
supportGenerator.supportTeethHeight = 1.5 # [mm] - Length of the support teeth
supportGenerator.supportTeethBaseInterval = 1.5 # [mm] - The interval between the support teeth
supportGenerator.supportTeethUpperPenetration = 0.2 # [mm] - The penetration of the support teeth into the part

supportGenerator.splineSimplificationFactor = 0.01 # - Specify the smoothing factor using spline interpolation for the support boundaries
supportGenerator.gridSpacing = [5,5] # [mm] The Grid

[drlukeparry]

I cannot understand or resolve issue because I cannot determine the orientation of the supports from the attached picture.

Please provide a full example with the model to verify the issue, including the versions of the libraries (including PySLM) that have been used in order to reproduce this.

[Vipul-M-Rawal]

I am using the given code. I have attached the model stl file along with the image :
`"""
Support generation script - Shows how to generate basic block supports using PySLM
"""

import numpy as np
import logging

from matplotlib import pyplot as plt
from pyslm.core import Part
import pyslm.support

import vispy
import trimesh
import trimesh.creation

"""
Uncomment the line below to provide debug messages for OpenGL - if issues arise.
"""

vispy.set_log_level('debug')

logging.getLogger().setLevel(logging.INFO)

CONSTANTS

OVERHANG_ANGLE = 55 # deg - Overhang angle

"""
Set the Geometry for the Example using a complicated topology optimised bracket geometry
"""
myPart = Part('myPart')
myPart.setGeometry("C:\Desktop\3-D Objects\Step.stl", fixGeometry=True)
#myPart.scaleFactor = 4.0
myPart.rotation = [0.0, 0.0, 0.0] #[62.0, 50.0, -40.0] #[10, 70, 30] #[62.0, 50.0, -40.0] #[-70.0, 50.0, -30.0] #[62.0, 50.0, -40.0]
#myPart.rotation = [76,35,-13] #[-25,0,5] #[76,35,-13]#[62,50,-40.0]

myPart.scaleFactor = 1.0
myPart.dropToPlatform(10)

""" Extract the overhang mesh - don't explicitly split the mesh"""
overhangMesh = pyslm.support.getOverhangMesh(myPart, OVERHANG_ANGLE,
splitMesh=False, useConnectivity=True)

overhangMesh.visual.face_colors = [254.0, 0., 0., 254]

"""
Generate the geometry for the supports (Point and Edge Over Hangs)
"""

First generate point and edge supports

pointOverhangs = pyslm.support.BaseSupportGenerator.findOverhangPoints(myPart)
overhangEdges = pyslm.support.BaseSupportGenerator.findOverhangEdges(myPart)

"""
Generate block supports for the part.

The GridBlockSupportGenerator class is initialised and the parameters below are specified as a reasonable starting
defaults for the algorithm. The GridBlockSupport generator overrides the BlockSupportGenerator class and provides
additional methods for generating a grid-truss structure from the support volume.
"""
supportGenerator = pyslm.support.GridBlockSupportGenerator()
supportGenerator.rayProjectionResolution = 0.05 # [mm] - The resolution of the grid used for the ray projection
supportGenerator.innerSupportEdgeGap = 0.3 # [mm] - Inner support offset used between adjacent support distances
supportGenerator.outerSupportEdgeGap = 0.3 # [mm] - Outer support offset used for the boundaries of overhang regions
supportGenerator.simplifyPolygonFactor = 0.5 # - Factor used for simplifying the overall support shape
supportGenerator.triangulationSpacing = 2.0 # [mm] - Used for triangulating the extruded polygon for the bloc
supportGenerator.minimumAreaThreshold = 0.1 # Minimum area threshold to not process support region'
supportGenerator.triangulationSpacing = 4 # [mm^2] - Internal parameter used for generating the mesh of the volume
supportGenerator.supportBorderDistance = 1.0 # [mm]
supportGenerator.numSkinMeshSubdivideIterations = 2

Support teeth parameters

supportGenerator.useUpperSupportTeeth = True
supportGenerator.useLowerSupportTeeth = True
supportGenerator.supportWallThickness = 1.0 # [mm] - The thickness of the upper and support walls to strengthen teeth regions
supportGenerator.supportTeethTopLength = 0.1 # [mm] - The length of the tab for the support teeth
supportGenerator.supportTeethHeight = 1.5 # [mm] - Length of the support teeth
supportGenerator.supportTeethBaseInterval = 1.5 # [mm] - The interval between the support teeth
supportGenerator.supportTeethUpperPenetration = 0.2 # [mm] - The penetration of the support teeth into the part

supportGenerator.splineSimplificationFactor = 10 # - Specify the smoothing factor using spline interpolation for the support boundaries
supportGenerator.gridSpacing = [5,5] # [mm] The Grid

"""
Generate a list of Grid Block Supports (trimesh objects currently). The contain the support volumes and other generated
information identified from the support surfaces identified on the part based on the choice of overhang angle.
"""
supportBlockRegions = supportGenerator.identifySupportRegions(myPart, OVERHANG_ANGLE, True)

for block in supportBlockRegions:
block.trussWidth = 1.0

blockSupports = [block.supportVolume for block in supportBlockRegions]

"""
Generate the edges for visualisation
"""
edges = myPart.geometry.edges_unique
meshVerts = myPart.geometry.vertices
centroids = myPart.geometry.triangles_center

if True:
""" Visualise Edges potentially requiring support"""
edgeRays = np.vstack([meshVerts[edge] for edge in overhangEdges])
visualize_support_edges = trimesh.load_path((edgeRays).reshape(-1, 2, 3))

edge_supports = []
for edge in overhangEdges:
    coords = np.vstack([meshVerts[edge,:]]*2)
    coords[2:,2] = 0.0

    extrudeFace = np.array([(0, 1, 3), (3, 2, 0)])
    edge_supports.append(trimesh.Trimesh(vertices=coords, faces=extrudeFace))

"""  Visualise Point Supports """

point_supports = []
cylinder_rad = 0.5 # mm
rays = []
for pnt in pointOverhangs:
    coords = np.zeros((2,3))
    coords[:,:] = meshVerts[pnt]
    coords[1,2] = 0.0

    point_supports += trimesh.creation.cylinder(radius = cylinder_rad, segment =coords)
    rays.append(coords)

# Alternatively can be visualised by lines
rays = np.hstack([meshVerts[pointOverhangs]]*2).reshape(-1, 2, 3)
rays[:, 1, 2] = 0.0
visualize_support_pnts = trimesh.load_path(rays)

Make the normal part transparent

myPart.geometry.visual.vertex_colors = [80,80,80, 125]

"""
Visualise all the support geometry
"""

""" Identify the sides of the block extrudes """
s1 = trimesh.Scene([myPart.geometry] + blockSupports)

"""
The following section exports the group of support structures from the trimesh scene.
"""

with open('overhangSupport.glb', 'wb') as f:
f.write(trimesh.exchange.gltf.export_glb(s1, include_normals=True))

"""
Show only the volume block supports generated
"""
DISPLAY_BLOCK_VOLUME = True

if DISPLAY_BLOCK_VOLUME:
s2 = trimesh.Scene([myPart.geometry, overhangMesh,
blockSupports])
s2.show()
`

Step.zip