Why targetRadius should be "43"?
Hi,
I am practicing C# by replicating a simple exercise in Monogame: the code draws a ball, and when I click on the mouse, if the cursor is inside the ball the score value increases; otherwise it does not.
To achieve this, the ball position was put in relation with a targetRadius, which is "43", and if I change the value it does not work anymore.
I am trying to understand what is happening here, why the radius should be "43" to have the things achieved?
The position of the ball and the radius are defined as follows:
Vector2 targetPosition;
const int targetRadius = 43;
Then the ball (target) is drawn by subtracting the radius from the coordinates of its position, why is it doing this?
_spriteBatch.Draw(target, new Vector2(targetPosition.X - targetRadius, targetPosition.Y - targetRadius), Color.Aquamarine);
It works, but I don't understand why..10 Replies
It is 2D or 3D? Do you have screenshot or something else to illustrate the ball, etc? It looks like 2D, because no
Z in your code but you called it a ball.It's 2D
yeah, you are right, actually it is a circle, not a ball
Could you send relevant code?
public class Game1 : Game
{
Texture2D target;
Vector2 targetPosition;
MouseState mouseState;
bool mouseReleased = true;
int score = 0;
const int targetRadius = 43;
private GraphicsDeviceManager _graphics;
private SpriteBatch _spriteBatch;
public Game1()
{
_graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
IsMouseVisible = true;
protected override void LoadContent()
{
_spriteBatch = new SpriteBatch(GraphicsDevice);
target = Content.Load<Texture2D>("target");
}
protected override void Update(GameTime gameTime)
{
mouseState = Mouse.GetState();
Vector2 mousePosition = mouseState.Position.ToVector2();
float mouseTargetDist = Vector2.Distance(targetPosition, mousePosition);
if (mouseTargetDist < targetRadius && mouseState.LeftButton == ButtonState.Pressed && mouseReleased == true)
{
score++;
mouseReleased = false;
}
if (mouseState.LeftButton == ButtonState.Released)
{
mouseReleased = true;
}
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
Vector2 targetPosition = new Vector2(100, 100);
_spriteBatch.Draw(target, new Vector2(targetPosition.X - targetRadius, targetPosition.Y - targetRadius), Color.Aquamarine);
_spriteBatch.End();
base.Draw(gameTime);
}
}
}What doesn't work anymore?
The origin in monogame is top left, not bottom left
Based on my investigation, I think the dimension of
target of type Texture2D is about 86 x 86 unit.
The inscribed circle in target has a diameter of 86 unit or its radius is 86 / 2 = 43.
If we want to make the center of target placed at (100, 100)
then its top left corner must be placed at (100 - 43, 100 - 43).
So your question:
Then the ball (target) is drawn by subtracting the radius from the coordinates of its position, why is it doing this?Because
_spriteBatch of type SpriteBatch must place the top left corner of target of type Texture2D at (100-43,100-43) to make the center of the target placed at (100, 100).
I'm not sure what that image is supposed to mean :thonk:
Why is the texture's center at 100,100
The circle is drawn using a texture, it's center would depend on how large the texture is
It could be 200x200 or 500x500
The overload for
Draw they used doesn't specify how large that drawn texture should beI guess
target's size is about 86 x 86 .
radius = 86 / 2 = 43 does make sense.