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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