Drawing problems with RenderTarget2D

Drawing problems with RenderTarget2D

• malindor

  That's exactly what I was looking for. Thank you for solution and explanation, I appreciate your help.
  
  

• Tufty

  SpriteBatch.Begin() method is equivalent as below.

  SpriteBatch.Begin(SpriteBlendMode.AlphaBlend, SpriteSortMode.Deferred, SaveStateMode.None)

  So, you are doing alpha blending when you render to the backbuffer. And, i assume your font drawing uses SpriteBatch too (Another alpha blending).

  I've confirmed that same symptoms occurred with your code. And that symptoms is gone when i use SpriteBatch.Begin(SpriteBlendMode.None) and change clear color from TransparentWhite to Navy.

  
  
  

• hypo

  Correct me if I'm wrong, but sounds like what you want to do is render text messages to the render target, then render it to the backbuffer.

  If so, you can use alpha test instead of alpha blending when you render messages to the render target. Then render that render target to the backbuffer with alpha blending.

  Here is code snipet to do that:

  // Font rendering to the render target.
  sb.Begin(SpriteBlendMode.None, SpriteSortMode.Immediate, SaveStateMode.None);
  graphics.GraphicsDevice.RenderState.AlphaTestEnable = true;
  graphics.GraphicsDevice.RenderState.ReferenceAlpha = 0;
  graphics.GraphicsDevice.RenderState.AlphaFunction = CompareFunction.Greater;

  // Render fonts with alpha test
  ....

  sb.End();

  // Render to the backbuffer.
  graphics.GraphicsDevice.ResolveRenderTarget(0);
  graphics.GraphicsDevice.SetRenderTarget(0, null);
  sb.Begin();
  sb.Draw(tex.GetTexture, New Vector2(0, 0), Color.White)
  sb.End();
  

  Key point is you have to specify SpriteSortMode.Immediate to overwrite render states. If you set other than SpriteSortMode.Immediate, SpriteBatch sets render states inside of SpriteBatch.End().

  
  
  

• Bandile

  I used:

  graphics.GraphicsDevice.Clear(Color.Navy)

  Is that correct

  
  
  

• Muhsin Zahid Uğur

  Do you clear the back buffer before you draw with the SpriteBatch
  
  

• crazyabtdotnet

  My guess is you are doing alpha blending twice.

  Say, You have a white (1,1,1) colored object with alpha value 0.5 and a render target that is filled by black. First time you render that object to render target, result becomes gray (0.5, 0.5, 0.5) colored object and also it stored alpha value to render target too.

  Now, when you use that render target as a texture with alpha blending, result becomes darkened gray (0.25, 0.25, 0.25) colored object.

  If this is the case, make sure you do alpha blending only once.

  
  
  

• gheese

  Thanks for answer, but it isn't probably my case. If you look closer on that picture (http://euroregin.net/heho/problem.jpg), you can see that "bottom version of text" is same, except that some pixels are less visible (after few same operations text almost disappear). So in my opinion it have to be something with alphablending, but I realy don't know why it's happening :(
  
  

• Miles100

  Hi Tomas,

  See my note at the bottom of http://blogs.msdn.com/manders/archive/2006/11/30/feedback-creating-chaos-with-render-to-texture.aspx (or the article it references, http://msdn.microsoft.com/archive/default.asp url=/archive/en-us/directx9_c_Feb_2006/Directly_Mapping_Texels_to_Pixels.asp).

  Hope this helps,

  -Mike

  
  

• Martin Lundberg

  Unfortunately that's not the problem. I created completely new project but everything is same:

  Protected Overrides Sub LoadGraphicsContent(ByVal loadAllContent As Boolean)

  If loadAllContent Then

  FontsLoad()

  tex = New RenderTarget2D(graphics.GraphicsDevice, 512, 256, 1, SurfaceFormat.Color, MultiSampleType.None, 0)

  sb = New SpriteBatch(graphics.GraphicsDevice)

  End If

  End Sub

  Protected Overrides Sub Draw(ByVal GameTime As GameTime)

  graphics.GraphicsDevice.Clear(Color.Navy)

• graphics.GraphicsDevice.SetRenderTarget(0, tex)

• graphics.GraphicsDevice.Clear(Color.TransparentWhite)

  font_verdana16.DrawString(10, 10, Color.White, "FPS:" & FPS)

  font_verdana8.DrawString(10, 40, Color.White, String.Format("Mouse X={0} Y={1}", Mouse.GetState.X, Mouse.GetState.Y))

• graphics.GraphicsDevice.ResolveRenderTarget(0)

• graphics.GraphicsDevice.SetRenderTarget(0, Nothing)

• sb.Begin()

• sb.Draw(tex.GetTexture, New Vector2(0, 0), Color.White)

• sb.End()

  MyBase.Draw(GameTime)

  End Sub

  If I remove lines with

• , everything is normal. Pls help