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.. _tut_ordinate_dimension:
Tutorial for Ordinate Dimensions
================================
Please read the :ref:`tut_linear_dimension` before, if you haven't.
.. note::
`Ezdxf` does not consider all DIMSTYLE variables, so the rendering results
are different from CAD applications.
Local Coordinate System
-----------------------
Ordinate dimensioning is used when the x- and the y-coordinates from a
location (feature), are the only dimensions necessary. The dimensions to each
feature, originate from one datum location, called "origin" in this tutorial.
The local coordinate system (LCS) in which the measurement is done,
is defined by the `origin` and the `rotation` angle around the z-axis in the
rendering UCS, which is the :ref:`WCS` by default.
Factory Methods to Create Ordinate Dimensions
---------------------------------------------
All factory methods for creating ordinate dimensions expect global coordinates
to define the feature location.
Global Feature Location
~~~~~~~~~~~~~~~~~~~~~~~
The first example shows ordinate dimensions defined in the render UCS,
in this example the :ref:`WCS`, this is how the DIMENSION entity expects the
coordinates of the feature location:
.. code-block:: Python
import ezdxf
from ezdxf.math import Vec3
from ezdxf.render import forms
# Use argument setup=True to setup the default dimension styles.
doc = ezdxf.new(setup=True)
# Add new entities to the modelspace:
msp = doc.modelspace()
# Add a rectangle: width=4, height = 2.5, lower left corner is WCS(x=2, y=3)
origin = Vec3(2, 3)
msp.add_lwpolyline(
forms.translate(forms.box(4, 2.5), origin),
close=True
)
# Add an x-type ordinate DIMENSION with global feature locations:
msp.add_ordinate_x_dim(
# lower left corner
feature_location=origin + (0, 0), # feature location in the WCS
offset=(0, -2), # end of leader, relative to the feature location
origin=origin,
).render()
msp.add_ordinate_x_dim(
# lower right corner
feature_location=origin + (4, 0), # feature location in the WCS
offset=(0, -2),
origin=origin,
).render()
# Add an y-type ordinate DIMENSION with global feature locations:
msp.add_ordinate_y_dim(
# lower right corner
feature_location=origin + (4, 0), # feature location in the WCS
offset=(2, 0),
origin=origin,
).render()
msp.add_ordinate_y_dim(
# upper right corner
feature_location=origin + (4, 2.5), # feature location in the WCS
offset=(2, 0),
origin=origin,
).render()
# Necessary second step to create the BLOCK entity with the dimension geometry.
# Additional processing of the DIMENSION entity could happen between adding
# the entity and the rendering call.
doc.saveas("ord_global_features.dxf")
The return value `dim` is **not** a dimension entity, instead a
:class:`~ezdxf.entities.DimStyleOverride` object is
returned, the dimension entity is stored as :attr:`dim.dimension`.
.. image:: gfx/dim_ord_global.png
Local Feature Location
~~~~~~~~~~~~~~~~~~~~~~
The previous examples shows that the calculation of the global feature location
is cumbersome and it gets even more complicated for a rotated LCS.
This example shows how to use a render :class:`~ezdxf.math.UCS` for using
locale coordinates to define the feature locations:
.. code-block:: Python
import ezdxf
from ezdxf.math import Vec3, UCS
from ezdxf.render import forms
doc = ezdxf.new(setup=True)
msp = doc.modelspace()
# Create a special DIMSTYLE for "vertical" centered measurement text:
dimstyle = doc.dimstyles.duplicate_entry("EZDXF", "ORD_CENTER")
dimstyle.dxf.dimtad = 0 # "vertical" centered measurement text
# Add a rectangle: width=4, height = 2.5, lower left corner is WCS(x=2, y=3),
# rotated about 30 degrees:
origin = Vec3(2, 3)
msp.add_lwpolyline(
forms.translate(forms.rotate(forms.box(4, 2.5), 30), origin),
close=True
)
# Define the rotated local render UCS.
# The origin is the lower-left corner of the rectangle and the axis are
# aligned to the rectangle edges:
# The y-axis "uy" is calculated automatically by the right-hand rule.
ucs = UCS(origin, ux=Vec3.from_deg_angle(30), uz=(0, 0, 1))
# Add a x-type ordinate DIMENSION with local feature locations:
# the origin is now the origin of the UCS, which is (0, 0) the default value of
# "origin" and the feature coordinates are located in the UCS:
msp.add_ordinate_x_dim(
# lower left corner
feature_location=(0, 0), # feature location in the UCS
offset=(0.25, -2), # # leader with a "knee"
dimstyle="ORD_CENTER",
).render(ucs=ucs) # Important when using a render UCS!
msp.add_ordinate_x_dim(
# lower right corner
feature_location=(4, 0), # feature location in the UCS
offset=(0.25, -2), # leader with a "knee"
dimstyle="ORD_CENTER",
).render(ucs=ucs) # Important when using a render UCS!
# Add a y-type ordinate DIMENSION with local feature coordinates:
msp.add_ordinate_y_dim(
# lower right corner
feature_location=(4, 0), # feature location in the UCS
offset=(2, 0.25), # leader with a "knee"
dimstyle="ORD_CENTER",
).render(ucs=ucs) # Important when using a render UCS!
msp.add_ordinate_y_dim(
# upper right corner
feature_location=(4, 2.5), # feature location in the UCS
offset=(2, 0.25), # leader with a "knee"
dimstyle="ORD_CENTER",
).render(ucs=ucs) # Important when using a render UCS!
doc.saveas("ord_local_features.dxf")
.. image:: gfx/dim_ord_local.png
Placing Measurement Text
------------------------
The `ezdxf` ordinate DIMENSION renderer places the measurement text always at
the default location, because the location of the leader end point is given by
the argument `offset` in the factory methods, which provides a flexible way
to place the measurement text, overriding the text location by an explicit
user location is not supported, also the user text rotation is not supported,
the text is always aligned to the local coordinate system x- and y-axis.
.. seealso::
- Graphical reference of many DIMVARS and some advanced information:
:ref:`dimstyle_table_internals`
- Source code file `standards.py`_ shows how to create your own DIMSTYLES.
- The Script `dimension_ordinate.py`_ shows examples for angular dimensions.
Overriding Measurement Text
---------------------------
See Linear Dimension Tutorial: :ref:`tut_angular_dim_overriding_text_rotation`
Measurement Text Formatting and Styling
---------------------------------------
See Linear Dimension Tutorial: :ref:`tut_measurement_text_formatting_and_styling`
Tolerances and Limits
---------------------
See Linear Dimension Tutorial: :ref:`tut_tolerances_and_limits`
.. _dimension_ordinate.py: https://github.com/mozman/ezdxf/blob/master/examples/render/dimension_ordinate.py
.. _standards.py: https://github.com/mozman/ezdxf/blob/master/src/ezdxf/tools/standards.py
|
