title: Particle System: XNA Framework HiDef profile does not support alpha blending on Vector4 textures
body: <p>I found this great tutorial on making a particle system in XNA:
  <a href="http://www.catalinzima.com/tutorials/4-uses-of-vtf/particle-systems/" rel="nofollow">http://www.catalinzima.com/tutorials/4-uses-of-vtf/particle-systems/</a></p>
  
  <p>The problem is that its written for an older version of xna and xna 4.0.</p>
  
  <p>In the DoPhysicsPass method I get this exception:</p>
  
  <p>XNA Framework HiDef profile does not support alpha blending or ColorWriteChannels when using rendertarget format Vector4.</p>
  
  <p>Here is the method that is blowing up</p>
  
  <pre><code>    private void doPhysicsPass(string technique, RenderTarget2D resultTarget)
      {
          GraphicsDevice.SetRenderTarget(temporaryRT);
          GraphicsDevice.Clear(Color.White);
          spriteBatch.Begin();
          physicsEffect.CurrentTechnique = physicsEffect.Techniques[technique];
          if (isPhysicsReset)
          {
              physicsEffect.Parameters["positionMap"].SetValue(positionRT);
              physicsEffect.Parameters["velocityMap"].SetValue(velocityRT);
          }
  
          physicsEffect.CurrentTechnique.Passes[0].Apply();
          spriteBatch.Draw(randomTexture, new Rectangle(0, 0, particleCount, particleCount), Color.White);
          spriteBatch.End(); //&lt;-----     Exception thrown here
  
          GraphicsDevice.SetRenderTarget(resultTarget);
          spriteBatch.Begin();
          physicsEffect.CurrentTechnique = physicsEffect.Techniques["CopyTexture"];
          physicsEffect.CurrentTechnique.Passes[0].Apply();
          spriteBatch.Draw(temporaryRT, new Rectangle(0, 0, particleCount, particleCount), Color.White);
          spriteBatch.End();
      }
  </code></pre>
  
  <p>Here is the initialization of randomTexture:</p>
  
  <pre><code>velocityRT = new RenderTarget2D(GraphicsDevice, particleCount, particleCount, false, 
                                  SurfaceFormat.Vector4, DepthFormat.None);
  </code></pre>
  
  <p>Can anyone offer some suggestions how to fix this?</p>