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gdevelop5:tutorials:basic-game-making-concepts [2019/07/09 04:30]
piyushpalawat99
gdevelop5:tutorials:basic-game-making-concepts [2020/01/11 01:31] (current)
4ian [Other ways of moving objects]
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 The basic concepts of GDevelop are simple. Read the following information to get started with the software. If you don't have GDevelop, [[https://​gdevelop-app.com/​download|download the latest version here]]! The basic concepts of GDevelop are simple. Read the following information to get started with the software. If you don't have GDevelop, [[https://​gdevelop-app.com/​download|download the latest version here]]!
  
-## Coordinates+## Showing things on the screen: the Objects 
 + 
 +Everything that is *displayed on the screen* is called an **"​Object"​**. Different kind of objects can be used to display different game elements on the screen. For example, most game graphics are "​Sprite"​ objects, texts can be displayed with "​Text"​ objects and special effects like a fire or sparks can be created with "​Particle Emitters"​. 
 + 
 +## Positioning Objects in the world: ​Coordinates
  
 Objects on the GDevelop screen/​scene have  X and  Y coordinates. These coordinates correspond to the horizontal position (X-axis) and the vertical position (Y-axis) on the //Cartesian plane//. Objects on the GDevelop screen/​scene have  X and  Y coordinates. These coordinates correspond to the horizontal position (X-axis) and the vertical position (Y-axis) on the //Cartesian plane//.
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 If you use trigonometric functions like the **sine** or the **cosine**, ​ you will need to express the angles in **radians**. (1 radian = 180/PI degrees and 1 degree = PI/180 radians. PI is the number which is approximately equal to 3.14159). If you use trigonometric functions like the **sine** or the **cosine**, ​ you will need to express the angles in **radians**. (1 radian = 180/PI degrees and 1 degree = PI/180 radians. PI is the number which is approximately equal to 3.14159).
  
-## Events and how objects are picked+## Events and how objects are selected by these Events
  
-Events, that you use to create the rules of your game, are composed of conditions and actions.+Events, that you use to create the rules of your game, are composed of conditions and actions. ​Most conditions and actions refer to objects: ​
  
-Most conditions and actions refer to objects. ​Conditions run a test on the objects. Actions manipulate the object.+Conditions run a **test** on the objects. ​ 
 +Actions ​**manipulate** the object. They can change the object position, appearance, etc...
  
 An action, without a condition, ​ refers to all objects. If you use an object for the first time in an event, GDevelop will test or modify **all objects** with this name in the scene. An action, without a condition, ​ refers to all objects. If you use an object for the first time in an event, GDevelop will test or modify **all objects** with this name in the scene.
 If you use the object in the same event again, GDevelop will test or modify only the objects which have been picked by the previous conditions. If you use the object in the same event again, GDevelop will test or modify only the objects which have been picked by the previous conditions.
  
-This process is an application of logic. ​For example, this event has no condition. It will delete **all** objects called "​Square":​+For example, this event has no condition. It will delete **all** objects called "​Square":​
  
 {{ :​gdevelop5:​tutorials:​delete-square.png?​nolink |}} {{ :​gdevelop5:​tutorials:​delete-square.png?​nolink |}}
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 ## Events: the order is important ## Events: the order is important
  
-**The order of events ​is critical!**+The order of events **does matter**!
  
 Events at the top are executed first. Events are executed every time your game is displayed. This display is called a frame. It executes about 60 times per second. The following examples are **not** equivalent: Events at the top are executed first. Events are executed every time your game is displayed. This display is called a frame. It executes about 60 times per second. The following examples are **not** equivalent:
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 * The second pair of events actions deletes all the "​Square"​ objects from the scene/​screen. It then creates one "​Square"​ at the scene/​screen coordinates X: 100, Y: 200 (100;​200). ​ This event shows a  square is  **visible** on the scene (before being deleted at the next frame. It will, then, be recreated immediately. * The second pair of events actions deletes all the "​Square"​ objects from the scene/​screen. It then creates one "​Square"​ at the scene/​screen coordinates X: 100, Y: 200 (100;​200). ​ This event shows a  square is  **visible** on the scene (before being deleted at the next frame. It will, then, be recreated immediately.
  
-## Moving objects using built-in forces+## Behaviors: pre-defined rules and logic for objects
  
-Moving objects can be achieved with **forces**. Forces are used to "​push"​ objects.+**Behaviors** allow to enhance an object with some *pre-defined logic*. Behaviors can be fairly simple, automating simple tasks or much more advancedFor example: ​
  
-You can specify:  +* A behavior ​can be used to automatically remove an object from the game when it goes out of the screen ​(limiting ​the game memory usage).  
-  * the Cartesian coordinates ​of a force (i.e. X and Y, in pixels). +The Physics behavior is an example of an advanced behavior which make your objects move in a realistic way, following ​the laws of physics.
-  * its polar coordinates ​(the force vector angle and length). +
-  * the **force damping**, a coefficient between 0 and 1+
  
-Each second, the force-length will be multiplied by the dispersiona value of 1 means that force will continue forever. A value of 0 will make it stop immediately. All intermediate values will cause the force to gradually stop.+Objects and Behaviors can be manipulated using events. You can read the pages about [[gdevelop5:objects|Objects]] and [[gdevelop5:​behaviors|Behaviors]] ​to know more about them.
  
-Some behaviors that you can add to your objects ​will move the objects ​by themselvesThis negates the need to use forcesIn this case see below:+## Moving ​objects: using the built-in forces 
 + 
 +Moving ​objects ​can be achieved with **forces**Forces are used to "​push"​ objects. 
 + 
 +You can specify 
 +  * the coordinates of a force on the X and Y axis, in pixels, 
 +  * or its polar coordinates (the force angle, in degrees, and length, in pixels), 
 +  * if the force is instant (will only push "a bit" the object) or continuous (will keep pushing the object until it's removed).
  
 ### Example ### Example
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 ### Other ways of moving objects ### Other ways of moving objects
  
-Some behaviors, like the Physics engine or Pathfinding,​ may move the objects by themselves. In this case, it is better not to use the builtin forces system and instead rely only on actions provided by the extensions used.+Some "behaviors", like the Physics engine or Pathfinding,​ may move the objects by themselves. In this case, it is better not to use the builtin forces system and instead rely only on actions provided by these behaviors.
  
 <note tip>​**See it in action!** 🎮Open this example online: https://​editor.gdevelop-app.com/?​project=example://​move-object-with-physics</​note>​ <note tip>​**See it in action!** 🎮Open this example online: https://​editor.gdevelop-app.com/?​project=example://​move-object-with-physics</​note>​
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 [[https://​editor.gdevelop-app.com/?​project=example://​move-object-with-physics|{{ :​gdevelop5:​tutorials:​moveobjectwithphysics.png |}}]] [[https://​editor.gdevelop-app.com/?​project=example://​move-object-with-physics|{{ :​gdevelop5:​tutorials:​moveobjectwithphysics.png |}}]]
  
 +<​note>​These other ways of moving objects are explained in [[gdevelop5:​tutorials:​how-to-move-objects|this how-to page]].</​note>​
  
- +## Storing any information in memory: ​Variables
-## Variables+
  
 A Variable allows you to store **data**. ​ For example, a variable can store a number or a text. We might compare them to drawers or boxes where we can file notes. Any data can be stored in a variable, as long as it is in //text// or //number// format. Such things as the number of lives a player has remaining, a player'​s high score, the number of bullets left, and/or the number of enemies killed are all examples of what can be stored in a variable. You are probably going to store numbers in variables as a common practice. A Variable allows you to store **data**. ​ For example, a variable can store a number or a text. We might compare them to drawers or boxes where we can file notes. Any data can be stored in a variable, as long as it is in //text// or //number// format. Such things as the number of lives a player has remaining, a player'​s high score, the number of bullets left, and/or the number of enemies killed are all examples of what can be stored in a variable. You are probably going to store numbers in variables as a common practice.
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 * **Object** variables only concern one object. For example, a hero can have a "​Health"​ or "​Ammo"​ variable. * **Object** variables only concern one object. For example, a hero can have a "​Health"​ or "​Ammo"​ variable.
  
-<​note>​Read more about variables on the [[gdevelop5:​all-features:​variables|Variables]] page. Variables are used a lot and you can see examples ​of all you can use them in most examples ​and in the tutorials.</​note>​ +<​note>​Read more about variables on the [[gdevelop5:​all-features:​variables|Variables]] page. Variables are used a lot in games: most examples use them and tutorials ​will make use of them too.</​note>​
-<note tip>Want to see how variables are used in a tutorial video? Check this tutorial [[https://​www.youtube.com/​watch?​v=SRfpBTgx-PY|Variables explained for Non-programmers]].</​note>​+
  
-## Time elapsed since last frame (TimeDelta)+<note tip>Want to see how variables are used in a video tutorial? Check this tutorial: ​ [[https://​www.youtube.com/​watch?​v=SRfpBTgx-PY|Variables explained for Non-programmers]].</​note>​ 
 + 
 +## An advanced notion: the "​time ​elapsed" ​since last frame (TimeDelta)
  
 The game evaluates events and repaints the screen several times per second: we say that the game is //​refreshed//,​ //updated// during a "​tick"​. How often this happens depends on your computer resources: a slow computer can render 25 frames per second, a fast one 60. GDevelop can usually make sure that this value is the same on all computers. However, the speed of some operations can change from computer to computer, for example, mathematical operations and the rendering of movements. The game evaluates events and repaints the screen several times per second: we say that the game is //​refreshed//,​ //updated// during a "​tick"​. How often this happens depends on your computer resources: a slow computer can render 25 frames per second, a fast one 60. GDevelop can usually make sure that this value is the same on all computers. However, the speed of some operations can change from computer to computer, for example, mathematical operations and the rendering of movements.
  
-To make the speed of changes constant, use the //​TimeDelta() expression//,​ which returns the time in seconds since the last frame.+To make the speed of changes constant, use the //`TimeDelta()expression//,​ which returns the time in seconds since the last frame.
 For example, don't do this: For example, don't do this:
  
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 * The second event is **correct and reliable** : The number 300 is multiplied by TimeDelta(). Thus, the variable will be increased at the same time on all computers. As  TimeDelta() returns a time in second, it allows you to quantify exactly the amount: In our case, the variable will grow at 300 units/​second. Thus, we can predicate that life will increase by 3000 units in 10 seconds - whatever the number of frames painted during this time. * The second event is **correct and reliable** : The number 300 is multiplied by TimeDelta(). Thus, the variable will be increased at the same time on all computers. As  TimeDelta() returns a time in second, it allows you to quantify exactly the amount: In our case, the variable will grow at 300 units/​second. Thus, we can predicate that life will increase by 3000 units in 10 seconds - whatever the number of frames painted during this time.
  
-**Remember:**  Use //​TimeDelta() // when you want to continually add some amount to a value. If your action is meant to be launched only once (for example, during a collision where you then delete the object), it's ok to use a discrete value without TimeDelta - as it does not depend ​upon the speed of the game.+<note tip>As GDevelop will run your game at a maximum of 60 images per second, you usually won't notice an issue if you're using the first event. It's still a good idea to keep an eye on this and use the version with `TimeDelta()` instead.</​note>​ 
 + 
 +**Rule of Thumb:**  Use //​TimeDelta() // when you want to continually add some amount to a value. If your action is meant to be launched only once (for example, during a collision where you then delete the object), it's ok to use a discrete value without TimeDelta - as it does not depend ​on the speed of the game.
  
 <note warning>​When you're moving an object using forces, there is no need to use TimeDelta() as GDevelop automatically uses it.</​note>​ <note warning>​When you're moving an object using forces, there is no need to use TimeDelta() as GDevelop automatically uses it.</​note>​
- 
-##Common conditions/​actions for all objects 
- 
-Every object has common conditions/​actions,​ **[[gdevelop5:​objects:​base_object:​events|read more about them here]]**. 
  
 ## And... that's almost all you need to know ## And... that's almost all you need to know