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Now that LPub is available for the Mac, fellow
Mac users may be excited to start creating instructions for your LDraw models.
If you’re like me, however, you might at first be perplexed about how to tell
LPub to show your model from different angles in different steps.
It turns out that this is accomplished with “ROTSTEP”, a meta-command borrowed
from MLCad. You can enter these statements
by hand, which is what I’ve done with the
instructions
I’ve created so far.
Here I will introduce you to ROTSTEP and provide some examples to illustrate how
it is applied. The ubiquitous CAR.DAT model has volunteered for example duty.
The Default View
Without any ROTSTEP statements, LPub renders models in this orientation:
We’ll experiment with RELative ROTSTEP statements, which will rotate the model
around the labelled axes defined by this default orientation.
The ROTSTEP Statement
Here is the general form of the ROTSTEP statements we will use:
0 ROTSTEP X Y Z REL
X, Y, and Z are the degree values that the model should be rotated around
the respective axes. For more information about other forms of the ROTSTEP
statement, consult the
MLCad extension
specification (PDF).
Refreshing Images in LPub
If you add ROTSTEP commands or otherwise modify the model using LPub’s editor
pane, you may need to refresh the images displayed for each step. First, click
the Tools menu and select “Clear Assembly Image Cache”:
Then click the “Redraw” button in the LDraw File toolbar. (It is the circular
arrow above the editor pane.) You don’t need to do this yet, but once you make
some changes you may need to.
90 Degree Rotation
Here are three screenshots showing the effects of 90 degree rotation about the
X, Y, and Z axes. Look carefully at the editor pane to see the corresponding
ROTSTEP statements - I’ve highlighted the key values.
Negative values rotate in the opposite direction. Notice that the rotation
remains in effect for subsequent steps.
Restoring or Changing the View
You can specify different rotations for as many steps as you want, of course.
Note that “0 ROTSTEP 0 0 0 REL” restores the original default view, as in the
second step of the above screenshot.
180 Degree Rotation
Here are a few more examples.
Experiment with different rotation increments. Try combining rotation about two
or more axes in one ROTSTEP statement.
An “Applied” Example
Here is a page from the instructions for my
Biplane
alternate model for the B-Wing Fighter.
I’ve flipped the model upside down with “0 ROTSTEP 0 0 180 REL” in step 4 to
reveal the pieces added to the bottom of the 4 x 6 plate.
Entering ROTSTEP Statements in Bricksmith
I’ve been learning how to use ROTSTEP statements by trial and error as I
experiment with LPub. As a result, I’ve been adding ROTSTEPs with LPub’s editor.
Once you get the hang of it, though, you may want to enter them right in
Bricksmith as you build the model.
Hold down the Option key while clicking the Model menu in Bricksmith to reveal
the “Insert Raw Command” command:
Double-click the new raw command item in the File Contents drawer and enter the
ROTSTEP statement:
Do not include the initial 0 when entering ROTSTEP statements this way.
Notes
These examples are based on LPub 4.0 and Bricksmith 2.0.
Please post any corrections, clarifications, or additional tips in reply!
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