DirectX11 problem with spacing while drawing lines - graphics

Question

I am facing an issue with blank spaces in my shapes (ex. triangle and circle). How should I deal with that problem?
Might it be because of antialiasing missing (if so how should i properly enable it for drawing such shapes)? Or is there a problem in my drawing method itself?
void graphics::draw_line_internal(int x0, int y0, int x1, int y1, rgba color)
{
if (this->initilized == false)
return;
UINT viewportNumber = 1;
D3D11_VIEWPORT vp;
this->device_context->RSGetViewports(&viewportNumber, &vp);
float xx0 = 2.0f * (x0 - 0.5f) / vp.Width - 1.0f;
float yy0 = 1.0f - 2.0f * (y0 - 0.5f) / vp.Height;
float xx1 = 2.0f * (x1 - 0.5f) / vp.Width - 1.0f;
float yy1 = 1.0f - 2.0f * (y1 - 0.5f) / vp.Height;
D3D11_MAPPED_SUBRESOURCE map_data;
this->device_context->Map(this->vertex_buffer.Get(), NULL, D3D11_MAP_WRITE_DISCARD, NULL, &map_data);
COLOR_VERTEX* v = NULL;
D3DXCOLOR cashed_color = color.convert_to_D3DXCOLOR();
v = (COLOR_VERTEX*)map_data.pData;
{
v[0] = { D3DXVECTOR3(xx0, yy0, 0) , cashed_color };
v[1] = { D3DXVECTOR3(xx1, yy1, 0) , cashed_color };
}
this->device_context->Unmap(this->vertex_buffer.Get(), NULL);
const float blend_factor[4] = { 0.f, 0.f, 0.f, 0.f };
this->device_context->OMSetBlendState(this->blend_state.Get(), blend_factor, 0xffffffff);
this->device_context->OMSetDepthStencilState(this->depth_stencil_state.Get(), 0);
this->device_context->IASetInputLayout(this->input_layout.Get());
UINT stride = sizeof(COLOR_VERTEX);
UINT offset = 0;
this->device_context->IASetVertexBuffers(0, 1, this->vertex_buffer.GetAddressOf(), &stride, &offset);
this->device_context->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_LINESTRIP);
this->device_context->VSSetShader(this->vertex_shader.Get(), NULL, 0);
this->device_context->PSSetShader(this->pixel_shader.Get(), NULL, 0);
this->device_context->OMSetRenderTargets(1, this->render_target_view.GetAddressOf(), NULL);
this->device_context->Draw(2, 0);
}
Line points from the screenshot are (20, 150) and (70, 20).

Answer 1

The most likely cause of your problem would be that the input data is incorrect. For the correct behaviour it must be guaranteed that xx1, yy1 of one segment is the same as xx0, yy0 of the next segment. However if I understand correctly the first image you provided was produced with one draw call? This seems to rule out this possibility.
In general black spots could be caused by garbage values in the depth stencil, but you are not using one :D . Additionally some of the segments in your images also have an offset to them. So this possibility is ruled out as well.
By the way the whole point of D3D11_PRIMITIVE_TOPOLOGY_LINESTRIP is to draw the entire curve at once. Just generate all points at once (without duplication), put them in a buffer, copy them to the GPU, and call Draw once. No funny business.
At this point I myself am quite lost in this whole situation. The only thing I can recommend is to disable everything but the essentials - shaders, input layout, vertex buffer and a render target - and look for a minimal repro.