Tag Archives: intermediate

GameMaker: Tower defense path-finding


Most of units turning back to take advantage of appearing hole in the maze

This example may be useful for ones making games of Tower Defense genre, as well as other games that require instances to dynamically re-adjust their path as new obstacles are being added.

System, included in this example, recalculates paths only when needed, thus providing minimum resource usage.
As well it detects if units have been blocked (to exclude possibility of cheating by enclosing units), and has a lesser sub-system to recycle & reuse paths.

Overall, should be intermediately useful.

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GameMaker: Pointing to an off-screen object


Illustration

This intermediate example demonstrates, how to create a rather nice interface element being an arrow that points between a on-screen object (normally player) and a off-screen location, that needs to be reached. In this case, arrow indicates exact direction to target, and is made to clamp accurately to screen edges (preserving direction vector), to avoid confusion on behalf of player.
Such feature is specifically useful for exploration games, where goal(s) may be at different distance from player, and some guidance is required.

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Source code follows,

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GameMaker: Orbiting


Interactive demo. Mouseover to activate, drag planets around.

This is an example of making an instance orbit around other instance in GameMaker.

In contrast to other similar examples (and commonly given advice of the kind), it allows to define orbiting speed in a common way (pixels/frame instead of degrees/frame).

This is accomplished by calculating the distance to orbit' center (from current position), calculating the orbit' length, and thus converting pixel speed to degree speed.

New position is then calculated and instance' speed is adjusted for it to reach it the next frame.
This allows to use direction in collision calculations as per usual.

Overall, the code is simple enough but documented regardless.

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Code follows,

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GameMaker: 8-way shooting with 4 keys


This is a specific example for shooting in 8 directions by having 4 'shoot' keys, which, in different combinations, determine direction. While not being exactly a common control scheme, in some situations this proves to be better than different schemes with single attack button, as it allows projectiles to be fired in directions independent from movement, essentially granting something similar to 'analog sticks' of gamepads.
Example is simple, well commented, and would be rather easy to implement.

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GameMaker: “notification” window


In the example, 'notifier' is just being annoying on purpose

This is an example for adding smooth-looking slide effect to game's window in GameMaker.
I suppose that ones to use my old program 'GMConverter' might have seen it there.
Despite of simplicity, it doesn't seem to be a common thing to see in games and applications.
Taking low ability of people to understand my original code, this example is well-commented and attempts to simplify usage where possible.

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GameMaker: Collision with 2d array


How it looks and how it is internally

This example demonstrates how to organize system where some level information is presented as a 2-dimensional array (item data indicating block index), and organize collisions with that.

Could basically say that this is a smaller version of my Terra example. Except simpler, using arrays, and Lite-compatible. As well it does not support truly infinite worlds (has a 32000x32000 limit), but target user is not likely to need that anyway.

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GameMaker: ‘strategy’ unit selection

Today I've made a simple example for strategy-like unit selection.
That is, selecting units (instances) with mouse, with selection rectangle and selected units being displayed accordingly.
Example is well-commented and should be easy to use.
Principle of work is simple - to detect units that overlap selection rectangle, game should cycle through them, performing collision_rectangle checks. Amount of calculations and code complexity is cut here by local variable usage (if you did not know, local variables 'var' will be available inside of with constructions without any prefixes).

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Source code follows,

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GameMaker: Taking screenshot of area larger than screen


Above: in-game view. Below: taken screenshot of entire room

This is an example that I've actually made a long time ago, but apparently it remains a common unresolved problem.
For multiple cases you may need to take a screenshot (or copy to surface) entire room, while only portion of it can be seen at once (window/screen size limitations).
A perfect work-around for this is to force screen drawing into a surface of chosen size, after adjusting view settings.

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GameMaker: Surfaces and scrollable content

In some cases, a moment comes when you need to display specific content in a area smaller than itself, thus requiring scrolling.

GameMaker does not support 'clip rectangle' type of command for its reasons, however it is easy to 'clip' area to be drawn by using an 'buffer' surface to draw content in, before drawing that to screen.
Attached example illustrates sample implementation of such.

Most often, content of such would be text. And maybe an image. Or two.

Since images would require a bit more code, example does simple and efficient - long long text is rendered into a surface, which is later drawn into an other 'buffer' surface to display it as part of window on screen.
Also there is a scrollbar, which obviously can be improved, if it needs to serve purposes other than displaying position of 'window'.

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