Method CreateBox

GTE/Graphics/MeshFactory.cpp:304–392

}

std::shared_ptr<Visual> MeshFactory::CreateBox(float xExtent, float yExtent, float zExtent)
{
    // Quantities derived from inputs.
    int32_t numVertices = 8;
    int32_t numTriangles = 12;

    // Generate geometry.
    auto vbuffer = CreateVBuffer(numVertices);
    if (!vbuffer)
    {
        return nullptr;
    }

    Vector3<float> pos{}, nor{};
    std::array<Vector3<float>, 3> basis{};
    Vector2<float> tcd{};

    // Choose vertex normals in the diagonal directions.
    Vector3<float> diag{ xExtent, yExtent, zExtent };
    Normalize(diag);
    if (!mOutside)
    {
        diag = -diag;
    }

    for (uint32_t z = 0, v = 0; z < 2; ++z)
    {
        float fz = static_cast<float>(z), omfz = 1.0f - fz;
        float zSign = 2.0f * fz - 1.0f;
        pos[2] = zSign * zExtent;
        nor[2] = zSign * diag[2];
        for (uint32_t y = 0; y < 2; ++y)
        {
            float fy = static_cast<float>(y);
            float ySign = 2.0f * fy - 1.0f;
            pos[1] = ySign * yExtent;
            nor[1] = ySign * diag[1];
            tcd[1] = (1.0f - fy) * omfz + (0.75f - 0.5f * fy) * fz;
            for (uint32_t x = 0; x < 2; ++x, ++v)
            {
                float fx = static_cast<float>(x);
                float xSign = 2.0f * fx - 1.0f;
                pos[0] = xSign * xExtent;
                nor[0] = xSign * diag[0];
                tcd[0] = fx * omfz + (0.25f + 0.5f * fx) * fz;

                basis[0] = nor;
                ComputeOrthogonalComplement(1, basis.data());

                SetPosition(v, pos);
                SetNormal(v, nor);
                SetTangent(v, basis[1]);
                SetBitangent(v, basis[2]);
                SetTCoord(v, tcd);
            }
        }
    }