Managed DirectX C# Graphics Tutorial 2: Drawing a Triangle

Now we’re going to look at drawing a triangle with Managed DirectX (MDX 1.1) using C#. The material presented here will strive to be the equivalent of the last tutorial which was in C++.

Requirements

The tutorial sample code was built and tested on Visual Studio 2008 Express. However, the code should work with 2005. You’ll also need the DirectX SDK August 2007 or earlier. I use June 2007 – you can download it with this link.

Tutorial Source and Project Files

To get the finished result of what this tutorial teaches – project files, binaries, and source – use this link:

• Download C# Sources and Binaries [~10k]

Getting Started

Everything involved with setting up the project, form, and DirectX will not be covered in this tutorial since it was already explained last time. See the “Managed DirectX C# Graphics Tutorial 1” if you want details on that.

In this post we’re going to take the code from the last tutorial and build off of it. We actually only need to change one function – OnPaint(). If you have the last tutorial’s project open, you can delete the contents of OnPaint. We’re going to replace those lines with stuff from the next section.

Define Vertices and Render

Unlike using DirectX in C++, there’s no need to define your own FVF vertex structure. Managed DirectX has pre-defined vertex types. The one we need to use in order to draw our triangle is represented by the “TransformedColored” struct. This struct is a nested entity inside the CustomVertex class. The CustomVertex class contains many struct’s representing common fixed-format vertex types. Basically, different vertex types that you’d commonly need to create using FVF codes in C++ are already defined by Managed DirectX.

There’s also no need to create a vertex buffer object like you would in native DirectX. You can use the original array of vertices and pass them directly into drawing routines. However, MDX still has the ability to work with vertex buffer objects if you need them.

These two major differences result in very simple drawing code. Drop the following code snippet into OnPaint() and you’re good to go:

CustomVertex.TransformedColored[] vertexes = new CustomVertex.TransformedColored[3];

 

vertexes[0].Position = new Vector4(50, 50, 0, 1.0f);
vertexes[0].Color = System.Drawing.Color.FromArgb(0, 255, 0).ToArgb();

vertexes[1].Position = new Vector4(250, 50, 0, 1.0f);
vertexes[1].Color = System.Drawing.Color.FromArgb(0, 0, 255).ToArgb();

vertexes[2].Position = new Vector4(50, 250, 0, 1.0f);
vertexes[2].Color = System.Drawing.Color.FromArgb(255, 0, 0).ToArgb();

 

m_device.Clear(ClearFlags.Target, System.Drawing.Color.FromArgb(0, 0, 0).ToArgb(), 1.0f, 0);
m_device.BeginScene();        
m_device.VertexFormat = CustomVertex.TransformedColored.Format;
m_device.DrawUserPrimitives(PrimitiveType.TriangleList, 1, vertexes);
m_device.EndScene();
m_device.Present();

The first line creates the vertex array while the next six lines fill in the information at each vertex (position and color). Then Clear() is called to erase the background. BeginScene() starts the 3D drawing code just like in C++. We tell DirectX about the vertex type being used by setting VertexFormat. This must match the vertex array element type. DrawUserPrimitives() takes the vertex array and renders the triangle. Finally we end the scene with EndScene() and show everything on the screen with Present(). What could be easier?

Full Listing

Since using .NET makes the text of this application so small, I’m going to list all the code here for your convenience.

using System;
using System.Windows.Forms;
using Microsoft.DirectX;
using Microsoft.DirectX.Direct3D;

 

namespace MDX_Tutorial2
{
   class MainClass:Form
   {
      private Device m_device = null;

 

      MainClass()
      {
         this.Text = “Managed DirectX Tutorial 2″;
      }

 

      void InitGraphics()
      {
         PresentParameters present_params = new PresentParameters();

         present_params.Windowed = true;
         present_params.SwapEffect = SwapEffect.Discard;

 

         m_device = new Device(0, DeviceType.Hardware, this,
                               CreateFlags.SoftwareVertexProcessing, present_params);
      }

 

      protected override void OnPaint(PaintEventArgs e)
      {
         CustomVertex.TransformedColored[] vertexes = new CustomVertex.TransformedColored[3];

 

         vertexes[0].Position = new Vector4(50, 50, 0, 1.0f);
         vertexes[0].Color = System.Drawing.Color.FromArgb(0, 255, 0).ToArgb();
         vertexes[1].Position = new Vector4(250, 50, 0, 1.0f);
         vertexes[1].Color = System.Drawing.Color.FromArgb(0, 0, 255).ToArgb();
         vertexes[2].Position = new Vector4(50, 250, 0, 1.0f);
         vertexes[2].Color = System.Drawing.Color.FromArgb(255, 0, 0).ToArgb();

 

         m_device.Clear(ClearFlags.Target, System.Drawing.Color.FromArgb(0, 0, 0).ToArgb(), 1.0f, 0);
         m_device.BeginScene();        
         m_device.VertexFormat = CustomVertex.TransformedColored.Format;
         m_device.DrawUserPrimitives(PrimitiveType.TriangleList, 1, vertexes);
         m_device.EndScene();
         m_device.Present();
      }

 

      static void Main()
      {
         MainClass MainForm = new MainClass();
         MainForm.InitGraphics();
         Application.Run(MainForm);
      }
   }
}

Program Output

Now for the fun part. What does running the program look like? Here’s a screenshot:

Look familiar? If it does, good. We set out to create the C# .NET equivalent of the C++ tutorial and did exactly that. If it looked different from last time, then we’d have a problem.

Conclusion

I hope you’ve gained insight into the differences and similarities of native DirectX versus Managed DirectX. If you have any questions or comments, please don’t hesitate to email me or leave a comment on this post.

Thanks for reading!

-Greg Dolley

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