Draw simple circle in XNA

I want to draw a 2d, filled, circle. I've looked everywhere and cannot seem to find anything that will even remotely help me draw a circl开发者_StackOverflow社区e. I simply want to specify a height and width and location on my canvas.

Anyone know how?

Thanks!

XNA doesn't normally have an idea of a canvas you can paint on. Instead you can either create a circle in your favorite paint program and render it as a sprite or create a series vertexes in a 3D mesh to approximate a circle and render that.

You could also check out the sample framework that Jeff Weber uses in Farseer:
http://www.codeplex.com/FarseerPhysics

The demos have a dynamic texture generator that let's him make circles and rectangles (which the samples then use as the visualization of the physics simulation). You could just re-use that :-)

Had the same problem, as others already suggested you need to draw a square or rectangle with a circle texture on it. Here follows my method to create a circle texture runtime. Not the most efficient or fancy way to do it, but it works.

Texture2D createCircleText(int radius)
{
    Texture2D texture = new Texture2D(GraphicsDevice, radius, radius);
    Color[] colorData = new Color[radius*radius];

    float diam = radius / 2f;
    float diamsq = diam * diam;

    for (int x = 0; x < radius; x++)
    {
        for (int y = 0; y < radius; y++)
        {
            int index = x * radius + y;
            Vector2 pos = new Vector2(x - diam, y - diam);
            if (pos.LengthSquared() <= diamsq)
            {
                colorData[index] = Color.White;
            }
            else
            {
                colorData[index] = Color.Transparent;
            }
        }
    }

    texture.SetData(colorData);
    return texture;
}

Out of the box, there's no support for this in XNA. I'm assuming you're coming from some GDI background and just want to see something moving around onscreen. In a real game though, this is seldom if ever needed.

There's some helpful info here:

http://forums.xna.com/forums/t/7414.aspx

My advice to you would be to just fire up paint or something, and create the basic shapes yourself and use the Content Pipeline.

Another option (if you want to use a more complex gradient brush or something) is to draw a quad aligned to the screen and use a pixel shader.

What I did to solve this was to paint a rectangular texture, leaving the area of the rectangle which doesn't contain the circle transparent. You check to see if a point in the array is contained within a circle originating from the center of the rectangle.

Using the color data array is a bit weird because its not a 2D array. My solution was to bring in some 2D array logic into the scenario.

public Texture2D GetColoredCircle(float radius, Color desiredColor)
    {
        radius = radius / 2;
        int width = (int)radius * 2;
        int height = width;

        Vector2 center = new Vector2(radius, radius);

        Circle circle = new Circle(center, radius,false);

        Color[] dataColors = new Color[width * height];
        int row = -1; //increased on first iteration to zero!
        int column = 0;
        for (int i = 0; i < dataColors.Length; i++)
        {
            column++;
            if(i % width == 0) //if we reach the right side of the rectangle go to the next row as if we were using a 2D array.
            {
                row++;
                column = 0;
            }
            Vector2 point = new Vector2(row, column); //basically the next pixel.
            if(circle.ContainsPoint(point))
            {
                dataColors[i] = desiredColor; //point lies within the radius. Paint it.
            }
            else
            {
                dataColors[i] = Color.Transparent; //point lies outside, leave it transparent.
            }
            
        }
        Texture2D texture = new Texture2D(GraphicsDevice, width, height);
        texture.SetData(0, new Rectangle(0, 0, width, height), dataColors, 0, width * height);
        return texture;
    }

And here's the method to check whether or not a point is contained within your circle:

 public bool ContainsPoint(Vector2 point)
    {
        return ((point - this.Center).Length() <= this.Radius);
    }

Hope this helps!

 public Texture2D createCircleText(int radius, GraphicsDevice Devise,Color color,int tickenes)
    {
        Texture2D texture = new Texture2D(Devise, radius, radius);
        Color[] colorData = new Color[radius * radius];
        if (tickenes >= radius) tickenes = radius - 5;
        float diam = radius / 2f;
        float diamsq = diam * diam;
        float intdiam = (radius-tickenes) / 2f;
        float intdiamsq = intdiam * intdiam;

        for (int x = 0; x < radius; x++)
        {
            for (int y = 0; y < radius; y++)
            {
                int index = x * radius + y;
                Vector2 pos = new Vector2(x - diam, y - diam);
                if (pos.LengthSquared() <= diamsq)
                {
                    colorData[index] = color;
                }
                else
                {
                    colorData[index] = Color.Transparent;
                }
                if (pos.LengthSquared() <= intdiamsq)
                {
                    colorData[index] = Color.Transparent; 
                }
            }
        }

        texture.SetData(colorData);
        return texture;
    }