Terrain only rendered underside - c++

Question

I'm trying to render a map, but unfortunately, only the underside is rendered.
I guess I'm doing something wrong while setting up the vertex and index buffers.
This is the part I initialize the vertex and index buffers:
// Initialize vertices and indices
SimpleVertex* vertices = new SimpleVertex[(dimension + 1) * (dimension + 1)];
WORD* indices = new WORD[dimension * dimension * 6];
for (WORD i = 0; i < dimension + 1; ++i)
{
for (WORD j = 0; j < dimension + 1; ++j)
{
vertices[i * (dimension + 1) + j].Pos = XMFLOAT3(i, rand() % 2, j);
vertices[i * (dimension + 1) + j].Color = XMFLOAT4(rand() % 2, rand() % 2, rand() % 2, 1.0f);
}
}
for (WORD i = 0; i < dimension; i++)
{
for (WORD j = 0; j < dimension; j++)
{
indices[(i * dimension + j) * 6] = (WORD)(i * (dimension + 1) + j);
indices[(i * dimension + j) * 6 + 2] = (WORD)(i * (dimension + 1) + j + 1);
indices[(i * dimension + j) * 6 + 1] = (WORD)((i + 1) * (dimension + 1) + j + 1);
indices[(i * dimension + j) * 6 + 3] = (WORD)(i * (dimension + 1) + j);
indices[(i * dimension + j) * 6 + 5] = (WORD)((i + 1) * (dimension + 1) + j + 1);
indices[(i * dimension + j) * 6 + 4] = (WORD)((i + 1) * (dimension + 1) + j);
}
}
// Create vertex buffer
D3D11_BUFFER_DESC bd;
ZeroMemory(&bd, sizeof(bd));
bd.Usage = D3D11_USAGE_DEFAULT;
bd.ByteWidth = sizeof(SimpleVertex)* (dimension + 1) * (dimension + 1);
bd.BindFlags = D3D11_BIND_VERTEX_BUFFER;
bd.CPUAccessFlags = 0;
D3D11_SUBRESOURCE_DATA InitData;
ZeroMemory(&InitData, sizeof(InitData));
InitData.pSysMem = vertices;
hr = g_pd3dDevice->CreateBuffer(&bd, &InitData, &g_pVertexBuffer);
delete vertices;
if (FAILED(hr))
return hr;
// Set vertex buffer
UINT stride = sizeof(SimpleVertex);
UINT offset = 0;
g_pImmediateContext->IASetVertexBuffers(0, 1, &g_pVertexBuffer, &stride, &offset);
// Create indices buffer
bd.Usage = D3D11_USAGE_DEFAULT;
bd.ByteWidth = sizeof(WORD)* dimension * dimension * 6;
bd.BindFlags = D3D11_BIND_INDEX_BUFFER;
bd.CPUAccessFlags = 0;
InitData.pSysMem = indices;
hr = g_pd3dDevice->CreateBuffer(&bd, &InitData, &g_pIndexBuffer);
delete indices;
if (FAILED(hr))
return hr;
Excuses for my bad English :(. Thank you for reading!

Answer 1

The first thing that occurred to me is you may be declaring your vertices in the wrong order. If your Direct3D context is expecting vertices to be counterclockwise, and yours are defined in clockwise order, "backface culling" will cause your polygons to be invisible unless viewed from the other side.
Specifically, D3D11_RASTERIZER_DESC::FrontCounterClockwise sets the direction. (see http://msdn.microsoft.com/en-us/library/windows/desktop/ff476198%28v=vs.85%29.aspx)
In the code where you set up your rasterizer description, try setting CullMode=D3D11_CULL_NONE and if the terrain appears, then this was your problem.

Answer 2

Most likely, the face culling wasn't set up properly.
In theory (thanks Google for providing links ;) ):
Face culling
Winding order
In practice:
You decide in which order to put your vertices within triangles (in reality, you manipulating with indices, as your buffers are indexed) - clockwise or counterclockwise.
Having decision #1 you now decide which faces must be considered as "front":
D3D11_RASTERIZER_DESC rd = {};
rd.FrontCounterClockwise = true; // counterclockwise are front
and you decide which faces rasterizer must cull: back ones, front ones, or none:
rd.CullMode = D3D11_CULL_BACK; // back faced primitives will be stripped out
// during rasterization
// (clockwise ones in our example)
So, you can either change your geometry winding and/or DirectX winding option and/or DirectX culling option.
Note: By-default, DirectX 11 uses false and D3D11_CULL_BACK for parameters above. So it considers clockwise primitives as front faced, and culls counterclockwise ones, considered back faced.
Note: To better understand culling, draw a triangle on both sides of piece of paper as if it would be same triangle viewed from different sides. Put indices near each vertex (same on both sides of paper). Draw an circular arrow showing winding order. Compare it with your mesh. Then it will be obvious which winding order and culling you must use.
Sources:
MSDN DirectX Reference pages:
D3D11_RASTERIZER_DESC
D3D11_CULL_MODE
ID3D11Device::CreateRasterizerState()
ID3D11DeviceContext::RSSetState()