Add Control Points to Levels.
Add Control Points to Levels
Control points are a wonderful new invention which allows aliens to follow you all over the
level without all that tedious mucking about in hyperspace. Erm.
Ok, what control points actually do is give the aliens a 'road map' of the level; sort of
invisible lines on the floor for them to trundle around. Such paths have been used in other
games to make aliens patrol around convincingly. The difference with AB3D is that the aliens
can use this map to get to you, if they know where you are, from the other side of the level,
assuming there is a path from where they are to where you are.
Also, if you make a sound somewhere near to an alien which is active, it will 'hear it' and
run to the control point it heard the sound coming from. If you continue shooting, therefore,
it will eventually make its way all the way over to where you are! In the diagram below, for
example, the player is standing near control point A. He has just fired his gun, and the
alien at point C will therefore run to control point B, which is the one towards where the player
is. When the alien reaches point B it will listen for the player to make more sounds, trying
to see if it can track him further. If it doesn't hear anything, it will wander off looking for
| +------------+ C
PLACING CONTROL POINTS
Control points must be joined with straight lines and MUST NOT cross walls which the aliens
cannot climb over. Therefore control points must be placed at all junctions and corners
so that aliens can navigate properly. Also, if you want aliens to venture into a dead end,
even if it is only a short one, you must put a control point near the end of the dead end.
1. To place control points, select the icon on the right hand end of the scrollable icon bar;
it looks like the 'add point' icon only with a pink dot rather than a green one.
2. Move the cursor into the edit area and click where you want to position a control point
with the mouse buttons. If you click the LEFT mouse button, the control point will be pink,
indicating that it is in the LOWER part of a zone. If instead you use the RIGHT mouse button,
the control point will be BLUE, indicating that it is in the upper part of the zone. Hence
you can cause aliens to navigate across winding gantries without falling off.
NB YOU CAN ONLY HAVE 100 CONTROL POINTS PER LEVEL SO USE THEM WISELY!
You can also MOVE control points by clicking on the 'O->' icon, grabbing a control point by
moving the cursor over it and pressing 'g', then placing it somewhere else by clicking with the
left or right mouse buttons as above.
LINKING CONTROL POINTS
So that the aliens can move around, you must link the control points together. There are two
ways they can be linked: PHYSICALLY or VISUALLY. Points linked PHYSICALLY describe a route for
walking aliens. Points linked VISUALLY describe extra routes for flying aliens. Hence if you have
a chasm with walkways on either side, the control points on each walkway would be linked visually,
because flying aliens could get across but walking aliens could not.
Control points which are linked PHYSICALLY are assumed to also be linked VISUALLY (but not the other
PHYSICAL links may be one-directional or two-directional. ONE directional links may only be
walked in one direction but are linked VISUALLY in both directions; TWO directional links may
be walked in both directions.
NB: If an alien cannot physically reach you (eg an impassable chasm or an unclimbable cliff), but
DOES know where you are, he may attempt to reach a position linked VISUALLY to your position
so he can take pot shots at you. To take a simple example: say the player is on top of a
cliff. Below him is a gorge, across which there is no bridge. There is a staircase leading
up to the OTHER side of the gorge from the bottom, but not up to the side the player is on.
Imagine there are several walking aliens with guns in the bottom of the gorge. The player
doesn't want to jump down with them still there, so he keeps popping out and shooting, then
ducking back out of harms way. The aliens cannot reach him, and nor can they see him properly
from the bottom of the gorge. They will therefore climb the staircase to the other rim of the
gorge where they can see the player and shoot at him!
1. Select the 'link control points' icon. This is near to the 'add control point' icon and looks
like a pink dot with three black lines radiating from it.
2. Clicking on a control point (say point A) and then on another (say point B) with the LEFT
mouse button toggles the PHYSICAL LINK from A to B. Clicking on them in the opposite order
toggles the link from B to A. To link them two-directionally, therefore, it is necessary to
click A, then B, then B again, and finally A. One-directional links are indicated by a red
arrow indicating the possible direction of travel; two directional links are indicated by
a blue, unarrowed line.
3. Clicking on a control point (A) and then on another (B) with the RIGHT mouse button toggles
the VISUAL link between the two points. If the two points are already linked visually, the
link will be removed. If they are linked physically in one or two directions, or not linked at
all, the existing link (or lack of it) will be replaced by a purple line indicating a VISUAL
Obviously it is unreasonable to expect someone to click-click-click their way through a room
containing 20+ control points, so it is only (usually) necessary to define the PHYSICAL links
by hand. The VISUAL links can be auto-generated by pressing RSHIFT and V together, with the cursor
somewhere in the edit area. Visual links will be automatically created between any points with a
line of sight between them which are not already linked physically. This takes a little while,
but console yourself with the thought that it's about 250,000 times faster than you could do it
NOTE: If you have a tall pillar with a control point on either side, then the autolinker WILL
link the two points, because there is no hole in the map seperating them. The ONLY time
the autolinker will not link points across a zone is if that zone's roof and floor are at the
same height; ie no travel across it is possible at ANY height.
ASSOCIATING CONTROL POINTS WITH ZONES:
Since you can have up to 256 zones but only 100 control points, it seems fairly obvious that
not all zones can have a control point in them. Therefore the question of which control point an
alien is nearest when standing in any particulat zone must be decided by you in advance.
This can be done in two ways, both of which begin by clicking on the 'associate zone with control
point icon (which looks like a small triangle near to a pink dot). Next, you either
1. Select a zone with the RIGHT mouse button and click on the control point you want to associate
with it with the LEFT mouse button. Make it a reasonable choice, ie don't pick a point on the
other side of a solid wall.
Repeat this process with each zone until you have covered the whole level.
UPPERS: This process is VERY accurate and yields the most bug-free maps.
DOWNERS: It takes AGES, and it's easy to forget to do certain bits of the map.
2. Press RSHIFT and A together with the cursor on the edit area. This will auto-associate zones
and control points. Again, this takes a little while but speeds things up a lot.
UPPERS: Takes no effort and doesn't miss anything out
DOWNERS: It can quite often make mistakes; linking zones to points not in visual sight of
I prefer to initially use method 2, then tidy up with method 1 if I notice any aliens stuck in
corners or walking into walls.
You must also link any upper parts of zones (eg gantries) with control points, and this must be
done manually because of the error-prone nature of the process. Select the 'link upper zone to
control point' icon (like the other one but with a double-triangle) and associate as before.
It is perfectly OK to link a lower zone to an upper control point or an upper zone to a lower
control point. See diagram for an explanation of why you might want to do this.
Zone A -> | *1 |
| # # |
| # # |
| Zone B -> # # |
| # # |
| # # |
| # # |
| Zone C -> # +2 # |
| # # |
Zone D -> | |
In the diagram point 2 (+) is a blue (upper zone control point), and point 1 (*) is a
pink, lower zone control point. Zones B and C comprise a gantry above a large room,
whilst zones A and D are corridors leading out onto that gantry. As you can see, given
the arrangement above, the upper part of zone C and the lower part of zone D should BOTH
be linked to point 2, and the lower part of zone A and the upper part of zone B should
both be connected to point 1.
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