Method CreateDisk

GTE/Graphics/MeshFactory.cpp:216–302

}

std::shared_ptr<Visual> MeshFactory::CreateDisk(uint32_t numShellSamples,
    uint32_t numRadialSamples, float radius)
{
    // Quantities derived from inputs.
    uint32_t ssm1 = numShellSamples - 1;
    uint32_t rsm1 = numRadialSamples - 1;
    float invSSm1 = 1.0f / static_cast<float>(ssm1);
    float invRS = 1.0f / static_cast<float>(numRadialSamples);
    uint32_t numVertices = 1 + numRadialSamples * ssm1;
    uint32_t numTriangles = numRadialSamples * (2 * ssm1 - 1);

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

    Vector3<float> pos;
    Vector3<float> nor{ 0.0f, 0.0f, 1.0f };
    Vector3<float> tan{ 1.0f, 0.0f, 0.0f };
    Vector3<float> bit{ 0.0f, 1.0f, 0.0f };  // = Cross(nor,tan)
    Vector2<float> tcd;

    // Center of disk.
    pos = { 0.0f, 0.0f, 0.0f };
    tcd = { 0.5f, 0.5f };
    SetPosition(0, pos);
    SetNormal(0, nor);
    SetTangent(0, tan);
    SetBitangent(0, bit);
    SetTCoord(0, tcd);

    for (uint32_t r = 0; r < numRadialSamples; ++r)
    {
        float angle = invRS * r * static_cast<float>(GTE_C_TWO_PI);
        float cs = std::cos(angle);
        float sn = std::sin(angle);
        Vector3<float> radial{ cs, sn, 0.0f };

        for (uint32_t s = 1; s < numShellSamples; ++s)
        {
            float fraction = invSSm1 * s;  // in (0,R]
            Vector3<float> fracRadial = fraction * radial;
            uint32_t i = s + ssm1 * r;
            pos = radius * fracRadial;
            tcd[0] = 0.5f + 0.5f * fracRadial[0];
            tcd[1] = 0.5f + 0.5f * fracRadial[1];

            SetPosition(i, pos);
            SetNormal(i, nor);
            SetTangent(i, tan);
            SetBitangent(i, bit);
            SetTCoord(i, tcd);
        }
    }

    // Generate indices.