Erwan's Blog

There are times where you need to get text input from the player like his name, etc.

Although this is possible to do it with XNA only, it is a bit of a hassle : you need to put a timer between each keystroke, etc and result is not perfect.

Lets use Nuclex framework.
Yes the same Nuclex we used in a previous article for gamepad inputs.

Code is rather simpler : we add a reference to nuclex framework, add an event handler and finally draw our string on screen. As simple as that !

Source is there : .XNA_DEMO_24
See vide lower in this article.


Imports Microsoft.Xna.Framework
Imports Microsoft.Xna.Framework.Graphics
Imports Microsoft.Xna.Framework.Audio
Imports Microsoft.Xna.Framework.Content
Imports Microsoft.Xna.Framework.Media
Imports Microsoft.Xna.Framework.Input
Imports Nuclex.Input

Public Class Game
Inherits Microsoft.Xna.Framework.Game
Dim graphics As GraphicsDeviceManager
Dim SpriteBatch As SpriteBatch
Dim input As InputManager
Dim myfont As SpriteFont
Dim msg As String
Dim dummyTexture As Texture2D
Public Sub New()
graphics = New GraphicsDeviceManager(Me)
input = New InputManager(Services, Window.Handle)
Components.Add(input)
Window.Title = "Test"
End Sub
Protected Overrides Sub Initialize()
MyBase.Initialize()
AddHandler input.GetKeyboard.CharacterEntered, AddressOf keyboardCharacterEntered
End Sub
Protected Overrides Sub LoadContent()
SpriteBatch = New SpriteBatch(GraphicsDevice)
myfont = Content.Load(Of SpriteFont)("xnb\myfont")
MyBase.LoadContent()
End Sub
Private Sub keyboardCharacterEntered(character As Char)
If Asc(character) = 8 Then
If msg.Length > 0 Then msg = msg.Remove(msg.Length - 1)
Else
If Asc(character) >= 32 And Asc(character) <= 126 Then msg += character End If End Sub Protected Overrides Sub UnloadContent() MyBase.UnloadContent() End Sub Protected Overrides Sub Update(ByVal gameTime As Microsoft.Xna.Framework.GameTime) MyBase.Update(gameTime) End Sub Protected Overrides Sub Draw(ByVal gameTime As Microsoft.Xna.Framework.GameTime) GraphicsDevice.Clear(Color.CornflowerBlue) SpriteBatch.Begin() If msg <> "" Then SpriteBatch.DrawString(myfont, msg, New Vector2(10, 10), Color.White)
SpriteBatch.End()
MyBase.Draw(gameTime)
End Sub
End Class


One thing that gives makes a game more dynamic is animated sprite.
Indeed, moving a fix shape all over the screen is nice. Moving an animated shape is better 🙂

Lets start with the below sprite sheet (yes it is link – hope no one will sue me for copyright infringement, this is only for educating purpose).

What we have here is 8 28*32 frames.
First frame is at position x=0, second frame at position x=28, third frame at position x=56, etc… you get the idea.
Which means that it we number our frame, we could easily get the position x=frame*28.

Second trick is one overloaded draw method which enables us to draw in a destination rectanble (on screen) from source rectangle (in a texture, our sprite sheet !).

Add to that some simple trick in the keyboard input where we would alternate two frames for one specific movement, and you obtain an animated sprite !

Source code : xna_demo_23.

A video (or screenshot) as always.

And the text source code if you want to have a quick glimpse at it.


Imports Microsoft.Xna.Framework
Imports Microsoft.Xna.Framework.Graphics
Imports Microsoft.Xna.Framework.Audio
Imports Microsoft.Xna.Framework.Content
Imports Microsoft.Xna.Framework.Media
Imports Microsoft.Xna.Framework.Input

A week ago, I posted an article about a basic car racing game I have written.

This time comes version 3.

-it uses a screenmanager (to manage several screens)
-it supports gamepad (any)
-it supports 2 players
-the car is now a class

A future version should support network gaming over tcpip.

Binary here : carv3 .
Remember that you have to install xna runtime.

If you are interested by the source code, contact me.
As always, any feedback, suggestions, ideas, remarks welcome!

Another needed feature in games is the ability to display multiple screens : intro, help, main game screen, etc …
For sure we could use one unique screen and redraw the whole thing each time but that would quickly become messy with lots of cases.

Here attached a demo that can be used as a basis.
As always our main module will call the first xna class (clsmain) : standard stuff.

From there we will call the menu screen.
In that screen, you can either call the help screen the game screen.
In these 2 screens, you can always go back to the menu screenpushing F10.

The code to go from one screen to the other is always :

my_screen_name= New class_name(Me.game)
ScreenManager.ShowScreen(my_screen_name)
Me.Close()


The source code : xna_demo_01 .
A project template to help starting new projects : XNA_SCREENMANAGER.

A video to illustrate.

In previous articles, we have seen many basics which should help to make a game : scrolling, moving shapes, collision, inputs (mouse, keyboard, gamepad)…

However, you may sometimes need to implement some physic principles : gravity, friction, restitution, etc.

This is where Farseer Physics Engine comes to the rescue.
Farseer Physics Engine is a collision detection system with realistic physics responses.

2 importants concepts to start with :
–World
The world object is the manager of it all. It iterates all the objects in the world each time you call the Step() function and makes sure everything is consistent and stable.
–Body
The body keeps track of world position. It is basically a point is space that is affected by forces such as impulses from collisions and gravity.

Lets add a project reference to farseer (note : I used msbuild /property:configuration=release « Farseer Physics XNA.csproj » to build it).
Then we will create a world, add a body to it and draw a texture based on the body position.

I encourage you to play with the world properties such as restitution, friction etc to see how it affects your world.
Also, notice how easy it is to detect collision (although I manage only plain shape for now, no convex shapes).

The source code : XNA_DEMO_19

A video to illustrate it.