Method CreateSphere

GTE/Graphics/MeshFactory.cpp:564–730

}

std::shared_ptr<Visual> MeshFactory::CreateSphere(uint32_t numZSamples,
    uint32_t numRadialSamples, float radius)
{
    // Quantities derived from inputs.
    uint32_t zsm1 = numZSamples - 1;
    uint32_t zsm2 = numZSamples - 2;
    uint32_t zsm3 = numZSamples - 3;
    uint32_t rsp1 = numRadialSamples + 1;
    float invRS = 1.0f / static_cast<float>(numRadialSamples);
    float zFactor = 2.0f / static_cast<float>(zsm1);
    uint32_t numVertices = zsm2 * rsp1 + 2;
    uint32_t numTriangles = 2 * zsm2 * numRadialSamples;

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

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

    // Generate points on the unit circle to be used in computing the mesh
    // points on a sphere slice.
    std::vector<float> cs(rsp1), sn(rsp1);
    for (uint32_t r = 0; r < numRadialSamples; ++r)
    {
        float angle = invRS * r * static_cast<float>(GTE_C_TWO_PI);
        cs[r] = std::cos(angle);
        sn[r] = std::sin(angle);
    }
    cs[numRadialSamples] = cs[0];
    sn[numRadialSamples] = sn[0];

    // Generate the sphere itself.
    uint32_t i = 0;
    for (uint32_t z = 1; z < zsm1; ++z)
    {
        float zFraction = -1.0f + zFactor*static_cast<float>(z);  // in (-1,1)
        float zValue = radius*zFraction;

        // Compute center of slice.
        Vector3<float> sliceCenter{ 0.0f, 0.0f, zValue };

        // Compute radius of slice.
        float sliceRadius = std::sqrt(std::max(radius * radius - zValue * zValue, 0.0f));

        // Compute slice vertices with duplication at endpoint.
        for (uint32_t r = 0; r <= numRadialSamples; ++r, ++i)
        {
            float radialFraction = r * invRS;  // in [0,1)
            Vector3<float> radial{ cs[r], sn[r], 0.0f };
            pos = sliceCenter + sliceRadius * radial;
            nor = pos;
            Normalize(nor);
            if (!mOutside)