ezdxf的座標系統

Table of contents

ezdxf的座標系統

背景

使用手冊
- object coordinate system (OCS)
- User coordinate system (UCS)
Tutorial

item	num
`[e for e in doc.modelspace()]`	3858
`[e for e in msp if e.dxf.layer=='98112']`	301
`len([e for e in msp if e.dxf.layer=='98112' and e.dxftype()=='POLYLINE'])`	277(其餘為`e.dxftype()`為`'TEXT'`)
`set([i.plain_text() for i in txt.plain_text()`	26~97共17個不連續值
`set([i.plain_text() for i in [e for e in msp if e.dxf.layer=='98111' and e.dxftype()=='TEXT']])`	20~95每隔5之整數字元、分散在65條`POLYLINE`
`[i for i in e.points()][:5]`	`[Vec3(313858.7020155214, 2771736.841981305, 86.0),...]` (‘TEXT’沒有`points()`)
`e.dxf.elevation`	`Vec3(0.0, 0.0, 86.0)`
`e.get_mode()`	`'AcDb2dPolyline'`

WCS to OCS

def wcs_to_ocs(point):
    px, py, pz = Vec3(point)  # point in WCS
    x = px * Ax.x + py * Ax.y + pz * Ax.z
    y = px * Ay.x + py * Ay.y + pz * Ay.z
    z = px * Az.x + py * Az.y + pz * Az.z
    return Vec3(x, y, z)

OCS to WCS

Wx = wcs_to_ocs((1, 0, 0))
Wy = wcs_to_ocs((0, 1, 0))
Wz = wcs_to_ocs((0, 0, 1))

def ocs_to_wcs(point):
    px, py, pz = Vec3(point)  # point in OCS
    x = px * Wx.x + py * Wx.y + pz * Wx.z
    y = px * Wy.x + py * Wy.y + pz * Wy.z
    z = px * Wz.x + py * Wz.y + pz * Wz.z
    return Vec3(x, y, z)

e.ocs()

['from_wcs',
 'points_from_wcs',
 'points_to_wcs',
 'render_axis',
 'to_wcs',
 'transform',
 'ux',
 'uy',
 'uz']

Tutorial for OCS/UCS Usage

Placing 2D Circle in 3D Space

import ezdxf
from ezdxf.math import OCS

doc = ezdxf.new('R2010')
msp = doc.modelspace()

# For this example the OCS is rotated around x-axis about 45 degree
# OCS z-axis: x=0, y=1, z=1
# extrusion vector must not normalized here
ocs = OCS((0, 1, 1))
msp.add_circle(
    # You can place the 2D circle in 3D space
    # but you have to convert WCS into OCS
    center=ocs.from_wcs((0, 2, 2)),
    # center in OCS: (0.0, 0.0, 2.82842712474619)
    radius=1,
    dxfattribs={
        # here the extrusion vector should be normalized,
        # which is granted by using the ocs.uz
        'extrusion': ocs.uz,
        'color': 1,
    })
# mark center point of circle in WCS
msp.add_point((0, 2, 2), dxfattribs={'color': 1})

3D Polyline

Using UCS to Place 3D Polyline

# using an UCS simplifies 3D operations, but UCS definition can happen later
# calculating corner points in local (UCS) coordinates without Vec3 class
angle = math.radians(360 / 5)
corners_ucs = [(math.cos(angle * n), math.sin(angle * n), 0) for n in range(5)]

# let's do some transformations by UCS
transformation_ucs = UCS().rotate_local_z(math.radians(15))  # 1. rotation around z-axis
transformation_ucs.shift((0, .333, .333))  # 2. translation (inplace)
corners_ucs = list(transformation_ucs.points_to_wcs(corners_ucs))

location_ucs = UCS(origin=(0, 2, 2)).rotate_local_x(math.radians(-45))
msp.add_polyline3d(
    points=corners_ucs,
    close=True,
    dxfattribs={
        'color': 1,
    }
).transform(location_ucs.matrix)

# Add lines from the center of the POLYLINE to the corners
center_ucs = transformation_ucs.to_wcs((0, 0, 0))
for corner in corners_ucs:
    msp.add_line(
        center_ucs, corner, dxfattribs={'color': 1}
    ).transform(location_ucs.matrix)

add_line

add_line(start: UVec, end: UVec, dxfattribs=None)→ Line¶
Add a Line entity from start to end.

Parameters:
start – 2D/3D point in WCS
end – 2D/3D point in WCS
dxfattribs – additional DXF attributes

points=[p for p in zip(xv,yv)]
M=len(points)
for i in range(M-1):
  msp.add_line(points[i], points[i+1], dxfattribs={"color": clrs[intv]})

add_polyline2d

add_polyline2d(points: Iterable[UVec], format: str | None = None, *, close: bool = False, dxfattribs=None)→ Polyline¶
Add a 2D Polyline entity.

Parameters:
points – iterable of 2D points in WCS(OCS)
close – True for a closed polyline
format – user defined point format like add_lwpolyline(), default is None
dxfattribs – additional DXF attributes

add_polyline3d

3d points in wcs(World coordinate system )

add_polyline3d(points: Iterable[UVec], *, close: bool = False, dxfattribs=None)→ Polyline¶
Add a 3D Polyline entity.

Parameters:
points – iterable of 3D points in WCS
close – True for a closed polyline
dxfattribs – additional DXF attributes

polyline.points()

points()→ Iterator[Vec3]¶
Returns iterable of all polyline vertices as (x, y, z) tuples, not as Vertex objects.

Tutorial for the Geo Add-on

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