DirectX Index Buffer Index order

Question

I'm having some trouble drawing with vertex and index buffers in DirectX.

Here is a function that defines a cube, but I've commented everything out but the front face:

void GeometryGenerator::CreateCube(MeshData& meshData)
    {
meshData.Vertices.resize(8);
meshData.Indices.resize(6);

float width;
float height;
float depth;

width = 45;
height = 45;
depth = 45;

XMFLOAT3 pos[8] = 
{
    XMFLOAT3(-0.5f * width, -0.5f * height, -0.5f * depth),
    XMFLOAT3(-0.5f * width, -0.5f * height,  0.5f * depth),
    XMFLOAT3(-0.5f * width,  0.5f * height, -0.5f * depth),
    XMFLOAT3(-0.5f * width,  0.5f * height,  0.5f * depth),
    XMFLOAT3( 0.5f * width, -0.5f * height, -0.5f * depth),
    XMFLOAT3( 0.5f * width, -0.5f * height,  0.5f * depth),
    XMFLOAT3( 0.5f * width,  0.5f * height, -0.5f * depth),
    XMFLOAT3( 0.5f * width,  0.5f * height,  0.5f * depth)
};

unsigned short k[6] = 
{
    ////1,0,2, // -x
    ////2,1,0,

    ////6,5,1, // +x
    ////6,7,5,
    ////
    ////0,1,5, // -y
    ////0,5,4,
    ////
    ////2,6,7, // +y
    ////2,7,3,

    ////4,6,0, // -z
    ////6,2,0,

    7,3,1, //+z
    5,7,1,
};

for(size_t i = 0; i < 8; ++i)
    meshData.Vertices[i].Position = pos[i];

for(size_t i = 0; i < 6; ++i)
    meshData.Indices[i] = k[i];

}

it draws one triangle and a line, neither of which go to the intended vertices. One triangle looks like it covers 7,3,0 and there is a line that covers 1,0. I have attached images below at 90 degree rotations:

I am happy to post whatever code is necessary, but I doubt you want me to post my entire project. A few things I think might be useful are......

My Vertex Struct:

struct Vertex
{   
DirectX::XMFLOAT3 pos;
DirectX::XMFLOAT3 color;
};

My Input layout:

    const D3D11_INPUT_ELEMENT_DESC vertexDesc[] = 
    {
        { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0,  D3D11_INPUT_PER_VERTEX_DATA, 0 },
        { "COLOR",    0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 12, D3D11_INPUT_PER_VERTEX_DATA, 0 },
    };

My Vertex Shader:

cbuffer ModelViewProjectionConstantBuffer : register(b0)
{
matrix model;
matrix view;
matrix projection;
};

struct VertexShaderInput
{
float3 pos : POSITION;
float3 color : COLOR0;
};

struct VertexShaderOutput
{
float4 pos : SV_POSITION;
float3 color : COLOR0;
};

VertexShaderOutput main(VertexShaderInput input)
{
VertexShaderOutput output;
float4 pos = float4(input.pos, 1.0f);

// Transform the vertex position into projected space.
pos = mul(pos, model);
pos = mul(pos, view);
pos = mul(pos, projection);
output.pos = pos;

// Pass through the color without modification.
output.color = input.color;

return output;
}

Primitive Topology:

m_d3dContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

Index Buffer Format:

m_d3dContext->IASetIndexBuffer(
    m_indexBuffer.Get(),
    DXGI_FORMAT_R16_UINT,
    0);

Vertex Stride and Offset:

UINT stride = sizeof(Vertex);
UINT offset = 0;
m_d3dContext->IASetVertexBuffers(
    0,
    1,
    m_vertexBuffer.GetAddressOf(),
    &stride,
    &offset);

Here is the DrawIndexed call:

m_d3dContext->DrawIndexed(
    m_Indices.size(),
    0,
    0);

The code that gets the data and creates the Index Buffer:

    GeometryGenerator generator;
    GeometryGenerator::MeshData cubeData;
    generator.CreateCube(cubeData);

            //m_Indices is a std::Vector<Vertex>
    m_Indices.resize(cubeData.Indices.size());

    for(size_t i = 0; i < cubeData.Indices.size(); i++)
        m_Indices[i] = cubeData.Indices[i];

    D3D11_SUBRESOURCE_DATA indexBufferData = {0};
    indexBufferData.pSysMem = &m_Indices[0];
    indexBufferData.SysMemPitch = 0;
    indexBufferData.SysMemSlicePitch = 0;

    const UINT indexBufferWidth = m_Indices.size() * sizeof(UINT);
    CD3D11_BUFFER_DESC indexBufferDesc(indexBufferWidth, D3D11_BIND_INDEX_BUFFER);
    DX::ThrowIfFailed(
        m_d3dDevice->CreateBuffer(
            &indexBufferDesc,
            &indexBufferData,
            &m_indexBuffer));

Thank you for the help! I have been working with "Introduction to 3D Game Programming with DirectX 11" by Frank Luna but I can't find any discussion on issues like these.

Answer 1

You are most likely making a mistake in one of the following. A mistake in any could easily cause the issue you are observing.

// Input layout defined correctly:
D3D11_INPUT_ELEMENT_DESC vertexDesc[] = { { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 } };

// Vertex shader input matches input layout:
VS_OUT main(float3 pos : POSITION)

// Primitive topology set correctly:
context->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

// Index buffer format set correctly:
context->IASetIndexBuffer(indexBuffer, DXGI_FORMAT_R16_UINT, 0);

// Vertex stride and offset set correctly:
UINT stride = sizeof(XMFLOAT3);
UINT offset = 0;
context->IASetVertexBuffers(0, 1, vertexBuffer, &stride, &offset);

// Draw arguments are correct:
context->DrawIndexed(6, 0, 0);