SharpDX: Enabling BlendState

Question

I'm trying to get the "SharpDX.Direct3D11.DeviceContext.OutputMerger.Blendstate" to work. Without this, i have nice scene (Polygones with textures on it, for a Spaceshooter). I've done OpenGL Graphics in the past three years, so i thought it might be as simple as in OpenGL - just enable Blending and set the right Dst/Src Modes. But if i set a new BlendStateDescription, all Output is Black, even if "RenderTarget[x].IsBlendEnabled" is set to "false". I searched for a tutorial or something, and find one - but it uses effects. So my question is simple - do i have to use technique's and effects in SharpDX? No other way left for simple blending?

This is what i've done:

mBackBuffer = Texture2D.FromSwapChain<Texture2D>(mSwapChain, 0);
mRenderView = new RenderTargetView(mDevice, mBackBuffer);
mContext.OutputMerger.SetTargets(mDepthStencilView, mRenderView);
mContext.OutputMerger.SetBlendState(new BlendState(mDevice, new BlendStateDescription()), new SharpDX.Color4(1.0f), -1);

mContext.OutputMerger.BlendState.Description.RenderTarget[0].IsBlendEnabled = true;
mContext.OutputMerger.BlendState.Description.RenderTarget[0].SourceBlend = BlendOption.SourceAlpha;
mContext.OutputMerger.BlendState.Description.RenderTarget[0].DestinationBlend = BlendOption.InverseSourceAlpha;
mContext.OutputMerger.BlendState.Description.RenderTarget[0].BlendOperation = BlendOperation.Add;           
mContext.OutputMerger.BlendState.Description.RenderTarget[0].SourceAlphaBlend = BlendOption.One;            
mContext.OutputMerger.BlendState.Description.RenderTarget[0].DestinationAlphaBlend = BlendOption.Zero;          
mContext.OutputMerger.BlendState.Description.RenderTarget[0].AlphaBlendOperation = BlendOperation.Add;          
mContext.OutputMerger.BlendState.Description.RenderTarget[0].RenderTargetWriteMask = ColorWriteMaskFlags.All;           

And, even if just simply do:

mContext.OutputMerger.SetBlendState(new BlendState(mDevice, new BlendStateDescription()), new SharpDX.Color4(1.0f), -1);
mContext.OutputMerger.BlendState.Description.RenderTarget[0].IsBlendEnabled = false;

ouput is all black.. maybe i just have to change something in the pixel shaders?

Answer 1

All resource in Direct3D11 are immutable, so when you are creating the new Blendstate(mDevice, new BlendStateDescription()), you cannot change the description later. The normal workflow is:

var blendDescription = new BlendDescription();
blendDescription.RenderTarget[0].IsBlendEnabled = .. // set all values 
[...]
var blendState = new BlendState(device, blendDescription);
context.OutputMerger.SetBlendState(blendState, ...);

Also resource objects need to be stored somewhere and disposed when you are completely done with them (most of the time for blendstates, at the end of your application), otherwise you will get memory leaks.

I advice you to look more closely at some Direct3D11 C++ samples when you are not sure about the API usage. Also, I recommend you to read a book like "Introduction to 3D Game Programming with DirectX 11" by Frank.D.Luna which is perfect to begin and learn the Direct3D11 API.