DrawLine function in XNA using Texture2D and SpriteBatch

A Simple DrawLine function is probably the base function for most of the typical Shape Drawing functions like DrawRectangle, DrawTriangle and DrawCircle. During my Editor project I wanted a tile to be marked by a red rect that should be drawn around a tile. Unfortunately XNA doesn not support simple shape drawing functions yet, so I decided to to some research and code them on my own. Of course many people recommended the "DrawPrimitive" way, using all the native 3D-Hardware methods but I wanted to use something more simple, because I didn´t need performance but easy-to-use stuff.

Since XNA makes Texture scaling so easy, another possibility is to just create a 1*1 white Texture2D and scale it to the length of the line and then rotate it, so it exactly looks like the line a normal DrawLine function would produce. In the end you have a very easy but still effective function that you can build on for other shape drawing functions like DrawRect which would simply contain of 4 calls for each edge.

Here is the code for this simple function - feel free to comment on improvments or ask questions:

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace Editor
{
   class XNAShape
   {
       Texture2D pixel;
       GraphicsDevice myDevice;

       public XNAShape(GraphicsDevice myDevice)
       {
           this.myDevice = myDevice;
           CreatePixelTexture();

           myDevice.DeviceReset += new EventHandler(myDevice_DeviceReset);
       }

       //Each time the device is reset, we need to recreate the Texture - otherwise it crashes in windowed mode
       void myDevice_DeviceReset(object sender, EventArgs e)
       {
           CreatePixelTexture();
       }

       //Creates a white 1*1 Texture that is used for the lines by scaling and rotating it
       public void CreatePixelTexture()
       {
           int TargetWidth = 1;
           int TargetHeight = 1;

           RenderTarget2D LevelRenderTarget = new RenderTarget2D(myDevice, TargetWidth, TargetHeight, 1,
               myDevice.PresentationParameters.BackBufferFormat, myDevice.PresentationParameters.MultiSampleType,
               myDevice.PresentationParameters.MultiSampleQuality, RenderTargetUsage.PreserveContents);

           DepthStencilBuffer stencilBuffer = new DepthStencilBuffer(myDevice, TargetWidth, TargetHeight,
               myDevice.DepthStencilBuffer.Format, myDevice.PresentationParameters.MultiSampleType,
               myDevice.PresentationParameters.MultiSampleQuality);

           myDevice.SetRenderTarget(0, LevelRenderTarget);

           // Cache the current depth buffer
           DepthStencilBuffer old = myDevice.DepthStencilBuffer;
           // Set our custom depth buffer
           myDevice.DepthStencilBuffer = stencilBuffer;

           myDevice.Clear(Color.White);

           myDevice.SetRenderTarget(0, null);

           // Reset the depth buffer
           myDevice.DepthStencilBuffer = old;
           pixel = LevelRenderTarget.GetTexture();
       }

       //Calculates the distances and the angle and than draws a line
       public void DrawLine(SpriteBatch sprite,Vector2 start, Vector2 end, Color color)
       {
           int distance = (int)Vector2.Distance(start, end);

           Vector2 connection = end - start;
           Vector2 baseVector = new Vector2(1, 0);

           float alpha = (float)Math.Acos(Vector2.Dot(connection, baseVector) / (connection.Length() * baseVector.Length()));

           if (pixel != null)
               sprite.Draw(pixel, new Rectangle((int)start.X, (int)start.Y, distance, 1),
                   null, color, alpha, new Vector2(0, 0),SpriteEffects.None, 0);
       }

       //Draws a rect with the help of DrawLine
       public void DrawRect(SpriteBatch sprite, Rectangle rect, Color color)
       {
           // | left
           DrawLine(sprite, new Vector2(rect.X, rect.Y), new Vector2(rect.X, rect.Y + rect.Height), color);
           // - top
           DrawLine(sprite, new Vector2(rect.X, rect.Y), new Vector2(rect.X + rect.Width, rect.Y ), color);
           // - bottom
           DrawLine(sprite, new Vector2(rect.X, rect.Y + rect.Height),
               new Vector2(rect.X + rect.Width, rect.Y + rect.Height), color);
           // | right
           DrawLine(sprite, new Vector2(rect.X + rect.Width, rect.Y),
               new Vector2(rect.X + rect.Width, rect.Y + rect.Height), color);

       }
   }
}

Written by verTex at 2:42 AM