Best data structure needed to create a game?
Blitz3D Forums/Blitz3D Programming/Best data structure needed to create a game?
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| there are some guidelines? who shared it? |
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| What exactly do you mean by Data Structure? Really, I suppose it depends on the game. I'm sure many might correct me or point out things I'm bnot aware of or such, but if I understand your question correctly: I find that when requiring data that may be added to or deleted continuously with no necessarily defined length or limit, or when multiple variable types associated are needed, Custom Types work best. When a fixed or known limit is required for a smaller variety of variable types, then I use arrays. For example, consider a "Space Invaders" game. there's a set limit on the number of aliens, so perhaps an array would suffice, whilst in a game such as "Asteroids" where asteroids are creaetd and destroyed all the time, then a Custom Type would suit. The manner in which these data are manipulated is another matter, and once more, very much down to the style of the game and personal preference. Any means of minimising iteration, or being able to identify object items directly is always advantageous. Overall, I'd say that some more info would be required to give you a more precise and relevant answer. |
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| With the name Data Structure i mean the structure of TYPE. Hovewer you have right intented what i mean. i wait an answer of this type... Yes i need some guidelines like advanced tutorials on platform but in general on some well used data structure used in games. thanks for your post malice. |
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| Introduction - What Are They? TYPE is your best friend. It is used to create a 'collection' of objects that share the same parameters and need to be interated through quickly and easily. Think about SPACE INVADERS. There are many aliens on the screen at one time. Each of these aliens have a few variables that they all need: x and y coordinates plus a variable to control which graphic to display (legs out or legs in). Now, we could make hundreds of variables like invader1x, invader1y, invader2x, invader2y, etc. to control all the aliens, but that wouldn't make much sense would it? You could use an array to track them; invader(number,x,y,graphic), and the loop through them with a FOR ... NEXT loop but that is a lot of work! The TYPE variable collection was created to handle just this sort of need. TYPE defines an object collection. Each object in that collection inherits its own copy of the variables defined by the TYPE's FIELD command. Each variable of each object in the collection can be read individually and can be easily iterated through quickly. Use the FIELD command to assign the variables you want between the TYPE and END TYPE commands. If it helps, think of a TYPE collection as a database. Each object is a record of the database, and every variable is a field of the record. Using commands like BEFORE, AFTER, and FOR ... EACH, you can move change the pointer of the 'database' to point to a different record and retrieve/set the variable 'field' values. Not a database guru? Need another example? Okay. Let's say you are setting up an auditorium for a speech or event and you are putting up hundreds of chairs for the spectators. The chairs have to be in a certain place on the floor, and some will need to be raised up a bit higher than others (visiting dignitaries, the mayor is coming, etc.). So being the computer genius you are, you start figuring out how you can layout the chairs with the least amount of effort. You realize that the floor is checkered, so its really a huge grid! This will make it easy! You just need to number the floor on a piece of graph paper and put into the grid how high each chair should be, based on where the boss told you the important people are to sit. So, for each chair, you will have a row and column on the graph paper (x and y location) and a level to adjust the chair to (height). Good, we are organized. Now, even though we have it all on paper, we still have to do the work of placing all the chairs. After you are done, let's say your boss walks up to you and says "they aren't centered right .. move'em all over 1 square". Ah crap! You have them all perfect, and even though it is a simple thing to move a chair one square to the right (after all, their order and height won't change) - you still have to move each and every chair! Should would be nice if you could just wave your hand and say "For each chair in the room, add 1 square to its x location" and have it just magically happen. Alas, in the real world, get busy - you've got a lot of chairs to move! In Blitz, you could have set up a TYPE called CHAIR, set the TYPE's FIELDS as X, Y, and HEIGHT. You would then create as many chairs as you need with the NEW command (each time you call NEW, it makes a new chair, with its OWN X, Y, and HEIGHT variables) and assign them the X, Y, and HEIGHT values you decide upon. In our example above, when the boss told you to move the chairs over 1 box, you probably groaned inside. That's a lot of work! In Blitz, we could use four lines of code to adjust all our CHAIR objects to the new position (using FOR ... EACH commands). Defining A Type Custom types are defined using the 'Type' keyword. For example: Type MyType Field x,y End Type Creates a custom type called 'MyType' with 2 fields - x and y. Fields within a custom type may themselves be of any basic type or custom type. Type tags are used to determine the type of a field. For example: Type MyType Field x,y Field description$ Field delta_x#,delta_y# End Type Creating a Type Instance You can create variables or arrays of custom types using a '.' type tag followed by the type name. For example: Global mine.MyType Dim all_mine.MyType( 100 ) Before a custom type variable or array element can be used, it must be initialized using the 'New' operator. For example: mine.MyType=New MyType The 'New' operator creates an 'object' of type 'MyType', and returns a 'pointer' to the new object. The identifier following the 'New' operator must be a valid custom type name. The fields within a custom type are accessed using the '\' character. For example: mine\x=100 Print mine\x Destroying a Type Instance When you've finished with an object, you should delete it using the 'Delete' command. For example: Delete mine This releases the memory used by the object. Determining Existance The special keyword 'Null' is used to represent non-existent objects. An object is non-existent if it hasn't been initialized yet using 'New', or has been released using 'Delete'. For example: mine.MyType=New MyType If mine<>Null Print "exists!" Else Print "doesn't exist!" EndIf Delete mine If mine<>Null Print "exists!" Else Print "doesn't exist!" EndIf ...will print the following: exists! doesn't exist! Each custom type has an associated list of objects known as a 'type list'. When an object is created using 'New', it is automatically added to the type list. When an object is released using 'Delete', it is removed from the type list. This list is dynamic - once an instance has been deleted, its place in the collection is deleted and all the other objects after it will 'move up' in the collection hiearchy. Iteration Through Type Lists The 'First', 'Last', 'After' and 'Before' operators allow you to access type lists. The 'First' operator returns the object at the start of the type list. For example: mine.MyType=First MyType This sets the 'mine.MyType' variable to the first object of custom type 'MyType'. Similarly, 'Last' returns the object at the end of the list. If the type list is empty, 'First' and 'Last' return 'Null'. You can use 'After' to find the object after an object, and 'Before' to find the object before an object. For example: mine.MyType=First MyType ;mine=first object in the type list mine=After( mine ) ;mine=second object mine=After( mine ) ;mine=third object mine=Before( mine ) ;mine=second object mine=Before( mine ) ;mine=first again! 'After' and 'Before' return 'Null' if there is no such object. For example: mine.MyType=Last MyType ;mine=last object mine=After( mine ) ;object after last does not exist! When an object is created using 'New', it is placed at the end of it's type list by default. However, You can move objects around within the type list using Insert. For example: mine1.MyType=New MyType mine2.MyType=New MyType Insert mine2 Before mine1 This has the effect of placing the 'mine2' object before the 'mine1' object in the type list. You can also use 'After' instead of 'Before' with Insert. Here's an example of moving an object to the start of it's type list: Insert mine Before First MyType A special form of For...Next allows you to easily iterate over all object of a custom type. For example: For mine.MyType=Each MyType Next This will cause the variable 'mine.MyType' to loop through all existing objects of cutom type MyType. Finally, the 'Delete Each' command allows you to delete all objects of a particular type. For example: Delete Each MyType |
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| @stanrol - you could have just linked to the blitz3d manual rather than copy the entire text... |
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| This is basic layout that I use - I have a type called "TYPE_game" that holds everything else, and there is then 1 global instance of that called "game" I then have other types setup for different objects, in this example there's one for my pacman called "TYPE_pacman", and there's an instance of this within the "game" object. I find that keeping everything within the one "game" instance makes it much easier to debug because it means you can't use a variable without first setting it up in the type, meaning typos are much less likely. Also it means you can clear and reset the game very quickly by just deleting and recreating the "game" type instance. Hope this makes some sense! Global game.TYPE_game Type TYPE_game Field CAM_camera1 Field CAM_orientation#[3] Field CAM_position#[3] Field LIGHT_light1 Field LIGHT_ambient[3] Field MESH_level Field pacman1.TYPE_pacman End Type Type TYPE_pacman Field pivot Field x# , y# , z# Field yaw# Field mesh_animmesh Field mesh_body_UPPER Field mesh_body_LOWER Field mouth_angle# Field mouth_direction End Type |
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| There is no right or wrong - its whatever works best for you. |
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| There is no right or wrong - its whatever works best for you. Seconded. I've changed my coding style, methods and indentation appearance over a dozen times since I started programming, and will probably continue to do so. :D |
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