Exercise 2 - Expanding the Map
Adding a Second Polygon
To
make the level behave properly, we need to add another polygon
connected to the first one. We'll add a corridor leading out of our
starting room and heading northwards.
Start by unhiding everything and rotating the view until you're looking at it like this:
What
we're aiming to do next is mark out an opening 1 world unit wide in the
middle of the southern wall. To do this accurately, we're going to use
the Tape Measure tool to draw some temporary construction lines. Go
slowly and pay careful attention to the following instructions, as they
need to be followed exactly to avoid going astray.
Switch to the Tape Measure tool
.
Move the mouse over the left-hand vertical edge of the southern wall,
but don't click anything yet. Watch until a red or cyan dot appears
over this edge, and a message which says either "On Edge" or
"Midpoint". Stay away from the endpoints of the edge. You're looking
for one of the following situations:

or

You also want there to be a + sign next to the tape measure cursor. If it's not there, tap the Option key (Alt on Windows) to make it appear.
When
both of these conditions are right, click and release the mouse, and
then move along the wall face in the direction of the red axis, until
you're about 1/3 of the way along. A vertical dashed guideline should
appear, snapped to a distance of 1 inch from where you started. Click
again to place the line.
Do the same thing again to create another guideline, but this time place it about 2/3 of the way along the face.
Now switch to the Pencil tool
.
Use it to draw a line from where the first guideline crosses the top
edge of the wall down to where it crosses the bottom edge. The tool
will snap to these intersection points. Do the same again for the other
guideline.
We're finished with the guidelines now, so we can delete them using the Edit>Delete Guides command. This leaves us with:
What we've just done is insert two new edges into the model, splitting what was formerly a single face into three faces.
Switch to the Push-Pull tool
and drag the middle face out until it snaps to a distance of 3 inches.
If this takes it beyond the window, click on Zoom Extents
so you can see the whole model again. It should look like this:
Before going any further, there's one thing we need to fix. Pulling out the wall face has
left us with floor and ceiling faces that are non-convex. If we tried
to export the model as it is, the exporter would try to create a single
non-convex polygon from them, which would violate the rules of Marathon
geometry.
So we need to divide the floor and ceiling into convex pieces. Switch
to the Pencil tool
and use it to draw a line between
the two ceiling vertices where the new corridor meets the old room. Make
sure the tool snaps to these vertices while you're doing this. The result should look like this:
We
need to do the same thing for the floor as well. Rotate the view up so
you can see the underside, and draw another line to cut the floor in
the same way.

Rotate the view back down again, and select and hide both of the new ceiling faces.
There's
one remaining thing to fix -- there's a spurious face in between the
two rooms. Select it and press the Delete key to get rid of it.
Adding a Monster
Let's
spice our corridor up a bit by adding an enemy to it. Rotate the view
down a little so you're looking down on the floor more. Now Copy and Paste
one of the Pfhor fighters from Objects.skp and position it on the floor
near the far end of the corridor. (Wait until you see an "On Face"
prompt before clicking to place it.)
Our
Pfhor is in the right place now, but he's facing in the wrong
direction. Fixing this will be easier if we zoom in on him. Switch
to the Zoom Window tool
and use it to drag out a rectangle around the area surrounding the fighter.
Make sure the fighter is still selected (there should be a blue rectangle around him) and switch back to the Move tool
.
Move it near the top of the blue rectangle and watch what happens. You
should see two red crosses appear, about 1/4 of the way in from each
end. (If you get four red crosses, keep moving until you're closer to
the top edge of the selection box.) This is what you want to see:
Now move the cursor onto one of the red crosses. A horizontal red protractor appears:
(If you get a green or blue protractor instead, you've got the wrong set of red crosses.)
Once
you've got the red protractor, click and drag in a circular motion. The
Pfhor rotates, snapping to the marks on the protractor. Turn him 90
degrees so he's facing down the corridor.
If you want, you can do the same thing with the Player object to change the direction the player is initially facing.
Testing Time Again
Export
the level, launch Aleph One, and you should be greeted by a Pfhor
running out of the corridor and attacking you. Beat him into submission
(or use your pistol if you're feeling wimpy), then you can go exploring
your new (slightly) expanded territory. You should find that the walls
are reassuringly solid this time!
When you get bored, you can move onto Exercise 3.
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