The DDHATCH command lets you setup the required crosshatch pattern and then create an
associate hatch region or replace the associate hatch of selected regions with it. The
same functionalities are also provided by the HATCH, RHATCH and CHANGE commands. However,
DDHATCH provides a much better user interface in specifying the crosshatch pattern.
DDHATCH will create and maintain its own private hatch pattern table out from the
current pattern file used by TwinCAD, and a slide library containing slides corresponding
to these patterns. If these informations can not be found from the installed directory or
are already out-of-date, DDHATCH will begin an initialization process first before
entering the service dialogue at its start-up. See latter section for more information
about the initialization process.
If everything is fine, DDHATCH will pop up the dialogue window as show below:
You may setup the required crosshatch pattern by selecting one from the predefined
patterns or by giving direct hatch line specifications, and then click at the [
Create] button to create a new hatch region to associate with it, or click at the
[Modify] button to select existing regions and to replace their associate hatch with it.
The following describes the details of these screen items from the top of the dialogue
Use Predefined Pattern
This group title is also an option check box. You may pick at it to toggle its checking
state. If this option is enabled (i.e. being checked), the predefined pattern specified in
this group will be used for the crosshatch and those items in this group will become
- Pattern A
combo-box type value field, specifying the name of the predefined pattern to use. You may
pick it by its drop-down button to select a name directly from a list of predefined
patterns. Or, you may pick it by its value box to choose the desired pattern from the
pop-up icon menu, as shown in the Example section.
- Size A value entry
field, specifying the size of the pattern in terms of the Minimum Y-interval of the
repeated lines in the pattern. Change this size value will also update the scale factor.
- Scale A value
entry field, specifying the scale factor of the pattern. Change this scale value will also
update the size value.
- Angle A value
entry field, specifying the rotation angle of the pattern in units of degrees.
The selected pattern will be shown in the preview sub-window with a slide from the
"DDHATCH.SLB" slide library, provided that it is present. Note that the effect
of the pattern scale and rotation angle is not reflected from the preview image. To
observe the true-size image of the resulting pattern, you may click the [Preview] button.
See latter paragraphs on the [Preview] button.
User-Defined Pattern Group
If the use of the predefined pattern is disabled, then user-defined pattern will be
used and the items from this group will become effective. A user-defined pattern is a
pattern defined by direct hatch line specifications. Each hatch line specification
contains the following three parts:
- Angle Direction
angle of the hatch line in units of degree.
- Spacing Offset
distance between each repeated hatch lines in drawing unit. This value can not be zero.
- Relative Alignments
Relative position with respect to a given alignment point that one of the repeated hatch
lines must pass through. This consists of two separate value entry fields, one for the
delta-X and the other, delta-Y.
For an associate hatch region using user-defined pattern, there can be at most three
distinct hatch line specifications. These are tabulated in this group. You can modify any
of these control values by clicking at the corresponding entry field. However, to make a
hatch line specification become effective, you have to check at its corresponding
The resulting pattern will be shown in the preview sub-window, provided that the use of
predefined pattern is disabled. Note that the true size of the pattern with respect to the
current drawing is determined by the spacing between hatching lines, and is not reflected
by the preview image. To observe the true-size image of the resulting pattern, you may
click the [Preview] button. See latter paragraphs on the [Preview] button.
Align Hatch Pattern
This is an option check box. If this option is enabled, you will be asked to designate
an alignment point when you click at the [Create] button to create a new associate hatch
region. DDHATCH will prompt:
Please designate pattern alignment base point:
The pattern alignment point is a point through which the pattern origin will pass. The
default will be at point (0,0).
This is an option check box. If this option is enabled, the associate hatch region
created will have a visible boundary; otherwise, the boundary will be invisible.
All associate hatch regions created by HATCH command are with invisible boundaries.
The [Sample] Button
You may click this button to sample an existing region entity from the drawing to setup
the current hatch specification. You will be asked to pick up the region entity by the
Please select the hatch region to sample:
DDHATCH will read the associate state of the region and set the current hatch
The [Preview] Button
You may click this button to view the physical size of the crosshatch pattern that
appears in the preview sub-window from the drawing. DDHATCH will create a box of
crosshatch and prompt
A 6-unit crosshatch is created at lower left corner...
Press space bar to end this crosshatch size preview:
You may enter ZOOM and PAN commands transparently to compare the crosshatch size with
respect to your current drawing or the targeted boundary area.
Although the appearance of the current hatch pattern specification, either from
predefined pattern or from direct hatch lines, can be observed from the preview
sub-window, the relative size of the pattern to the current drawing may still not be
clearly visualized. If the pattern size is too small, i.e. small scale factor or too
narrow line spacing, the crosshatch will be too dense to have any meaning other than
solid, let along the time to generate it. If it is too large, the effect of the crosshatch
may not be so obvious.
Therefore, you may need to physically observe the relative size of the crosshatch to
the current drawing, to determine a proper size for it.
The [Modify] Button
You may click this button to select region entities, modify their states of
associativity by the current hatch specification and end the DDHATCH command operation.
You will be asked to select region entities by the prompt:
Select Regions to Modify (+):
DDHATCH will terminate after the operation completes.
The [Create] Button
You may click this button to create a new regional area of crosshatch and end the
DDHATCH command operation. DDHATCH will internally call BPOLY command first for you to
define the regional area. See BPOLY command for details of the command operation.
After the region entity is created by the BPOLY command, DDHATCH will apply the current
setting of hatch specification to it and end the command operation.
You may press the [Help] button to see the helping text. Press the [Quit] button to end
DDHATCH immediately. Pressing <ESC> key also quits DDHATCH.
DDHATCH requires additional informations from the following two disk files:
- Pattern Table: A file containing a compacted informations about the current loaded hatch
patterns in TwinCAD. It must have the same path name as the current loaded pattern file
but with a different file extension as "DDH".
- Slide Library: A file containing corresponding slides to these predefined patterns. It
must be "DDHATCH.SLB" and be located in one of the search path of TwinCAD.
If DDHATCH can not find and load in the Pattern Table, or the Pattern Table is
out-of-date because the pattern file had been updated, DDHATCH will issue the message:
** Initialize DDHATCH ...
and begin to create a new pattern table.
After the pattern table is created or loaded in, DDHATCH will search for the
"DDHATCH.SLB" slide library and check to see if there are corresponding slides
in it to each of the predefined hatch patterns. If this slide library is missing, or there
is at least one slide missing (maybe due to new pattern definition added to the pattern
file), DDHATCH will pop up a query dialogue asking you if you want DDHATCH to build one or
to add new slides for you.
Note that, without the corresponding slide, you won't be able to view the predefined
pattern from the preview sub-window. However, if you like, you may create the required
slides using MSLIDE command and update the "DDHATCH.SLB" slide library using the
DOS utility ASLIDE.EXE all by yourself.
If you permit, DDHATCH will create slides for each corresponding predefined hatch
patterns and save them into the "DDHATCH.SLB" slide library automatically. This
requires the DOS utility ASLIDE.EXE be located from the search paths.
Since the aspect ratio of the slide to create has better be the same as that of the
preview sub-window which is about square, you may have to adjust the window frame of
TwinCAD such that the drawing window is about square for better slide generation.
DDHATCH will prompt
** Before generating the required slide ...
Please adjust the drawing window to about square:
You may press the space bar to proceed the slide generation.
The DDHATCH command is an external command provided by the TCL program file
"DDHATCH.TCL" or "DDHATCH.TCA". Either file must be present in the
COMMANDS sub-directory where the TwinCAD resides. If you can not issue DDHATCH command,
you may resolve the problem by copying the "DDHATCH.TCL" to the COMMANDS