I tried to draw a line between two vertices with D3D11. I have some experiences in D3D9 and D3D11, but it seems to be a problem in D3D11 to draw a line, which starts in one
I don't know D3D11, but your problem sounds a lot like the D3DRS_LASTPIXEL render state from D3D9 - maybe there's an equal for D3D11 you need to look into.