private void BlendTextures()
{
	RenderToSurface rts = new RenderToSurface(_device, _textureSize, _textureSize, Format.A8R8G8B8, true, DepthFormat.D16);

	Surface surfaceCombined;

	VertexBuffer vb = GraphicsUtility.CreateTransformedQuad(Pool.Managed, _textureSize, Color.White, _device, new Point3D(0.0f, 0.0f, 1.0f));
	surfaceCombined = _textureCombined.GetSurfaceLevel(0);

	Viewport vp = new Viewport();
	vp.Width = _textureSize;
	vp.Height = _textureSize;
	vp.MaxZ = 1.0f;

	rts.BeginScene(surfaceCombined, vp);

	_device.Clear(ClearFlags.Target | ClearFlags.ZBuffer, Color.Transparent, 1.0f, 0);

	_device.SetStreamSource(0, vb, 0);
	_device.VertexFormat=CustomVertex.TransformedColoredTextured.Format;
  
	_device.RenderState.AlphaBlendEnable = true;
	_device.RenderState.AlphaTestEnable = false;
	_device.RenderState.TextureFactor = Color.FromArgb(_alphaBlendFactor, Color.White).ToArgb(); // the _alphablendfactor increases every frame...

	_device.RenderState.SourceBlend = Blend.SourceAlpha;
	_device.RenderState.DestinationBlend = Blend.InvSourceAlpha;
	_device.TextureState[0].ColorOperation = TextureOperation.Modulate;
	_device.TextureState[0].ColorArgument1 = TextureArgument.TextureColor;

	_device.TextureState[1].ColorOperation = TextureOperation.BlendFactorAlpha;
	_device.TextureState[1].ColorArgument1 = TextureArgument.TextureColor;

	_device.SetTexture(0, _texture);
	_device.DrawPrimitives(PrimitiveType.TriangleFan, 0, 2);

	_device.SetTexture(1, _texture2);
	_device.DrawPrimitives(PrimitiveType.TriangleFan, 0, 2);

	rts.EndScene(Filter.None);

	surfaceCombined.Dispose();
	vb.Dispose();
	rts.Dispose();
}