Develop Reference

Moving Draw() code to a Class

I'm creating a game in monogame, and I've loaded tiles in my game inside the Draw() function like so:
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
spriteBatch.Draw(danChar, charPosition, Color.White);
// loop below loads the 'grass' tiles only
// assuming gameworld size of 770x450
for (int i = 0; i < 770; i += 31) // adds 31 to i (per tile)
{
position = new Vector2(i, 392); // places incrementation into vector position
spriteBatch.Draw(gameTile, position, Color.White); // draws the tile each time
if (i == 744)
{
i = i + 26; // fills last space between 744 and 770
position = new Vector2(i, 392);
}
spriteBatch.Draw(gameTile, position, Color.White);
}
// loop below loads the brick tiles only (ones without grass)
spriteBatch.End(); // ends the spriteBatch call
base.Draw(gameTime);
}
However I would prefer that this was a separate class rather than being placed directly into the draw function, however I'm not too sure how to do this and would appreciate any help given.
Thanks in advance!

If you just want to move the code as is to another class, create your class (e.g. something like GameWorld seems to appropriate for your code)
public class GameWorld
{
// You may wish to move your gameTile definition into this class if it is the only
// class that uses it, and handle the content loading for it in here.
// e.g. if you're currently loading the texture in the LoadContent method in your game
// class, create a LoadContent method here and pass in ContentManger as a parameter.
// I've passed in the texture as a parameter to the Draw method in this example to
// simplify as I'm not sure how you're managing your textures.
public void Draw(SpriteBatch spriteBatch, GameTime gameTime, Texture2D gameTile)
{
// loop below loads the 'grass' tiles only
// assuming gameworld size of 770x450
for (int i = 0; i < 770; i += 31) // adds 31 to i (per tile)
{
Vector2 position = new Vector2(i, 392); // places incrementation into vector position
spriteBatch.Draw(gameTile, position, Color.White); // draws the tile each time
if (i == 744)
{
i = i + 26; // fills last space between 744 and 770
position = new Vector2(i, 392);
}
spriteBatch.Draw(gameTile, position, Color.White);
}
// loop below loads the brick tiles only (ones without grass)
}
}
Then the Draw method in your Game class would look like
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
spriteBatch.Draw(danChar, charPosition, Color.White);
// Assuming you've created/loaded an instance of the GameWorld class
// called gameWorld in Initialize/LoadContent
gameWorld.Draw(spriteBatch, gameTime, gameTile);
spriteBatch.End(); // ends the spriteBatch call
base.Draw(gameTime);
}
Just make sure you're calling the Draw methods in the correct order. e.g. you want your player to appear above any background tiles.
I believe the default SpriteSortMode is Deferred which draws in the order the calls are made (i.e. from the back to the front).
You can specify a different SpriteSortMode in your call to spriteBatch.Begin() if you need to but for a simple game just move the Draw calls around.
More info on SpriteSortMode at MSDN if needed.
Similarly you can chain your Update, LoadContent methods into these classes if you wish, making sure to pass in anything you need as arguments.
Update:
To define gameWorld as an instance of the GameWorld class, you define it near the top of your game class, then typically initialize it in the Initialize method.
So your game class will look something like
public class MyGameName : Microsoft.Xna.Framework.Game
{
private SpriteBatch spriteBatch;
// other variable declarations
// Add a declaration for gameWorld
private GameWorld gameWorld;
protected override Initialize()
{
// Add the following line to initialize your gameWorld instance
gameWorld = new GameWorld();
}
// other existing code - your LoadContent, Update, Draw methods etc.
}

Redraw only one texture, not all of them

I'm a little noob with XNA and I've encountered a problem. I have one texture called "dot", that I use to draw a line across the screen. Then I have a texture that I call "tool", that I want to move around when I touch it with my finger. The problem I have is that for the tool to be cleared and redrawn I call the graphicsDevice.Clear-method in XNA. But when I do that, my lines also disappears. So my question is how can i move around the tool, without causing my lines to disappear? Is there a way to only redraw the tool, without redrawing the lines? Heres a snippet of my code, first update-method:
protected override void Update (GameTime gameTime)
{
float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
TouchCollection touchCollection = TouchPanel.GetState ();
foreach (TouchLocation tl in touchCollection) {
if ((tl.State == TouchLocationState.Pressed) || (tl.State == TouchLocationState.Moved)) {
toolPos = touchCollection [0].Position;
}
}
base.Update (gameTime);
}
And the draw-method:
protected override void Draw (GameTime gameTime)
{
graphics.GraphicsDevice.Clear (Color.Black);
newVector = nextVector (oldVector);
spriteBatch.Begin ();
DrawEvenlySpacedSprites (dot, oldVector, newVector, 0.9f);
spriteBatch.Draw (tool, toolPos, Color.White);
spriteBatch.End ();
oldVector = new Vector2 (newVector.X, newVector.Y);
base.Draw (gameTime);
}

Try using a RenderTarget2D with RenderTargetUsage.PreserveContents. If you didn't use render targets yet, here's a tutorial: http://rbwhitaker.wikidot.com/render-to-texture
All you have to do is to specify RenderTargetUsage.PreserveContents in target's constructor, draw dots to it, and draw the target and tool to the screen. It should look like this:
protected override void Draw (GameTime gameTime)
{
graphics.GraphicsDevice.Clear (Color.Black);
newVector = nextVector (oldVector);
GraphicsDevice.SetRenderTarget(renderTarget);
spriteBatch.Begin ();
DrawEvenlySpacedSprites (dot, oldVector, newVector, 0.9f);
spriteBatch.End ();
GraphicsDevice.SetRenderTarget(null);
spriteBatch.Begin();
spriteBatch.Draw(renderTarget, new Vector2(), Color.White);
spriteBatch.Draw (tool, toolPos, Color.White);
spriteBatch.End()
oldVector = new Vector2 (newVector.X, newVector.Y);
base.Draw (gameTime);
}

XNA - weird frame rate drop when using Draw and DrawString together

I have a Board class in my game. This Board class is responsible for drawing a number of Zone objects, which currently all have the same texture.
So my draw calls go like: Game1.Draw calls Board.Draw which calls Zone.Draw for every zone object, which calls Spritebatch.Draw
Draw method of Game1
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.Black);
spriteBatch.Begin(SpriteSortMode.Deferred, null, null, null, null, null, cam.Transform);
board.Draw(gameTime);
spriteBatch.End();
}
Draw method in Board class (Board.Draw)
public void Draw(GameTime gameTime)
{
if (zones != null)
{
for (int x = 1; x < xbound-1; x++)
{
for (int y = 1; y < ybound-1; y++)
{
zones[x, y].Draw(gameTime);
}
}
}
}
Draw method in Zone (Zone.Draw)
public void Draw(GameTime gameTime)
{
if (Tile != null)
{
Game1.spriteBatch.Draw(Tile, new Rectangle((int)pos.X, (int)pos.Y, size, size), Color.White);
//Game1.spriteBatch.DrawString(font2, pos.X.ToString() + "," + pos.Y.ToString(), pos, Color.Blue);
}
}
Everything works fine until I start drawing strings. Uncommenting the DrawString call results in a catastrophic FPS drop from consistent 60 to 20-25.
But here's the weird part. I created a different method for drawing the strings, instead of doing it in Zone's Draw. I called this method after Board.Draw finished drawing the Zones.
New seperate method for drawing the strings
public void DrawNumbers(GameTime gameTime)
{
if (zones != null)
{
for (int x = 1; x < xbound - 1; x++)
{
for (int y = 1; y < ybound - 1; y++)
{
Game1.spriteBatch.DrawString(font2, x.ToString() + "," + y.ToString(), zones[x, y].getPos(), Color.Blue);
}
}
}
}
Now Game1's Draw looks like this
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.Black);
spriteBatch.Begin(SpriteSortMode.Deferred, null, null, null, null, null, cam.Transform);
board.Draw(gameTime);
spriteBatch.End();
spriteBatch.Begin(SpriteSortMode.Deferred, null, null, null, null, null, cam.Transform);
board.DrawNumbers(gameTime);
spriteBatch.End();
}
Doing it this way provides no performance hit! I get constant 60FPS again, which sounds counter-intuitive for me...
Any idea why its doing this? Why does calling DrawString right after a Draw call seem to be so costly?
Please edit or inquire if the question isn't clear.
Thanks in advance.

The fact that you're interspersing Draw() with DrawString() is a bit of a red herring; the relevant fact here is that you're repeatedly swapping textures.
Your zone objects are all on one texture. So when you first draw all the zones, and then draw all of the strings, this is what's happening in the video driver:
OK, we're about to draw polygons using zoneTexture. Set up our device state.
Draw all of the zone polygons.
Now we're going to draw polygons using fontTexture. Set up our device state.
Draw all of the string polygons.
Done.
On the other hand, when you intersperse your text with your zones, it looks more like this:
OK, we're about to draw polygons using zoneTexture. Set up our device state.
Draw the polygons for Zone 1.
Hold on, we've got to draw some text using fontTexture. Set up our device state.
Draw the polygons for the text for Zone 1.
OK, we've still got more zones to draw using zoneTexture. Set up our device state.
Draw the polygons for Zone 2.
Oops, Zone 2 also has text using fontTexture. Set up our device state.
Draw the polygons for the text for Zone 2.
OK, time for the next zone using zoneTexture. Set up our device state.
And on, and on, and on...
As you can see, interspersing Draw() calls which require different device states forces the graphics driver to do a heck of a lot more work! So that's why you're seeing a drop in FPS.

Draw() method in XNA stops working inside a for loop

So far, this is my first XNA game and I'm having real trouble trying to learn this.
I'm following a tutorial from Microsoft, found here: XNA Xbox Live Indie Games
Every now and again, the code breaks. Admittedly, I have taken a couple of bits out that I didn't think I'd need and I've created two enemy classes rather than just the one, but I don't think I hit any major faultlines with my adjustments.
In the Draw() method in the main Game1.cs file, I've had to include a for loop that will iterate through a list of available enemies and draw them upon update. However, the line of code flags up as incorrect, and I have absolutely no idea why. I followed the tutorial, and it looks like it should work, but it doesn't. Here's the entire Draw() method:
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.ForestGreen);
backRect.Width = 800;
backRect.Height = 480;
// TODO: Add your drawing code here
// Start drawing
spriteBatch.Begin();
spriteBatch.Draw(backgroundTexture, backRect, Color.White);
// Draw the Player
player.Draw(spriteBatch);
for (int i = 0; i < goblins.Count; i++)
{
goblins[i].Draw(spriteBatch);
}
// Stop drawing
spriteBatch.End();
base.Draw(gameTime);
}
It's the code inside the for loop that won't work. Any ideas how to fix it and/or any suggestions for a better tutorial?

I like this tutorial a lot:
http://xbox.create.msdn.com/en-US/education/tutorial/2dgame/getting_started
It got me started off pretty well.

You always need to call SpriteBatch.Begin() and SpriteBatch.End() on your sprite-batches. I am not sure about mixing them, but try to avoid it and use as few spritebatches as possible.
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.ForestGreen);
backRect.Width = 800;
backRect.Height = 480;
// TODO: Add your drawing code here
// Start drawing
spriteBatch.Begin();
spriteBatch.Draw(backgroundTexture, backRect, Color.White);
// Draw the Player
spriteBatch.Draw(playerTexture, playerRect, Color.White);
for (int i = 0; i < goblins.Count; i++)
{
spriteBatch.Draw(goblins[i].Texture, goblins[i].Rect, Color.White);
}
// Stop drawing
spriteBatch.End();
base.Draw(gameTime);
}
See here for the documentation.

adding a 2D Sprite with a mouse click

i'm just beginning to code in C# / XNA
I've made a very simple little program in XNA, its a drawn rectangle, with 3 randomly generated balls inside,
the balls are defined in their own class and I've been following this tutorial
http://www.bluerosegames.com/brg/xna101.aspx
the balls are generated using
int ballCount = 3;
and what i wanted to do is make it so a mouse click would increase the int by 1, adding another ball to the screen
my code looks like this, but I'm not sure if it's right / possible
mouseStateCurrent = Mouse.GetState();
if (mouseStateCurrent.LeftButton == ButtonState.Pressed &&
mouseStatePrevious.LeftButton == ButtonState.Released)
{
ballCount = ballCount+1;
}
mouseStatePrevious = mouseStateCurrent;
any help advice would be helpful :)
i am using a code to draw the balls already that looks like this
spriteBatch.Begin();
spriteBatch.Draw(debugColor, TextBox, Color.White);
spriteBatch.Draw(background, backgroundRectangle, Color.White);
foreach (BouncingBall ball in balls)
{
ball.Draw(spriteBatch);
}
spriteBatch.End();
base.Draw(gameTime);
is it possible to edit this to get the "click to add balls" effect?

If balls is defined as a List<BouncingBall> that is accessible to the Game class, in your MouseClick event you can use balls.Add(new BouncingBall());. Because you are using a foreach loop, it will increment the number of balls each loop and your Draw code will already cater for any new balls added.

In your draw method you can do something like
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
for(var i=0;i<ballcount;i++)
{
spriteBatch.Draw()
}
spriteBatch.End();
base.Draw(gameTime);
}