plane subdivision

https://stackoverflow.com/a/19781416

 

3d plane을 여러개의 패치로 나누는 코드..

vertex가 좀 중복되긴 하는데.. 이건 코드 수정을 하면 해결..

#include <iostream>
#include <array>
#include <string>
#include <vector>


using Position3 = std::array<float, 3>;
using Plane = std::array<Position3, 4>;

Position3& operator *= (Position3& pos, const float scale)
{
    for (auto& x : pos) x *= scale;
    return pos;
}

Position3 operator * (const Position3& pos, const float scale)
{
    Position3 result = pos;
    result *= scale;
    return result;
}

Position3& operator += (Position3& left, const Position3& right)
{
    for (size_t i = 0; i < 3; i++)
        left[i] += right[i];

    return left;
}

Position3 operator + (const Position3& left, const Position3& right)
{
    Position3 result = left;
    result += right;
    return result;
}

Position3& operator -= (Position3& left, const Position3& right)
{
    for (size_t i = 0; i < 3; i++)
        left[i] -= right[i];

    return left;
}

Position3 operator - (const Position3& left, const Position3& right)
{
    Position3 result = left;
    result -= right;
    return result;
}


/* vertices by index in quad:
    3---------2
    |         |
    |         |
    |         |
    0---------1
*/
std::vector<Plane> subdivide(const Plane& plane, size_t iterations = 1)
{
    if (iterations == 0)
    {
        return{ plane };
    }
    else
    {
        Position3 e1 = plane[1] - plane[0];
        Position3 e2 = plane[2] - plane[3];
        Position3 e3 = plane[3] - plane[0];
        Position3 e4 = plane[2] - plane[1];

        Position3 p1 = e1 * 0.5f + plane[0];
        Position3 p2 = e2 * 0.5f + plane[3];
        Position3 p3 = e3 * 0.5f + plane[0];
        Position3 p4 = e4 * 0.5f + plane[1];

        Position3 e5 = p2 - p1;
        Position3 p5 = e5 * 0.5f + p1;

        std::vector<Plane> result{
            { plane[0], p1, p5, p3 },
            { p1, plane[1], p4, p5 },
            { p5, p4, plane[2], p2 },
            { p3, p5, p2, plane[3] }
        };

        if (iterations == 1)
        {
            return result;
        }
        else
        {
            std::vector<Plane> result2;
            for (auto& x : result)
            {
                auto subplanes = subdivide(x, iterations - 1);
                result2.insert(result2.end(), subplanes.begin(), subplanes.end());
            }
            return result2;
        }
    }
}

int main()
{
    Plane p = { { { 0, 0 }, { 1, 0.5f }, { 1, 1 }, { -0.5f, 1.5f } } };

    auto subd = subdivide(p, 2);

    std::string vertices;
    std::string faces;

    size_t idx = 1;
    for (auto& plane : subd)
    {
        for (auto& pos : plane)
            vertices.append("v  ").append(std::to_string(pos[0])).append(" ").append(std::to_string(pos[1])).append(" ").append(std::to_string(pos[2])).append("\n");

        faces.append("f ").append(std::to_string(idx)).append(" ").append(std::to_string(idx + 1)).append(" ").append(std::to_string(idx + 2)).append(" ").append(std::to_string(idx + 3)).append("\n");

        idx += 4;
    }
    std::string obj = vertices + "\n\n" + faces;

    std::cout << obj;
}

set -x ; clang++ -std=c++11 -O2 -pthread main.cpp && ./a.out
+ clang++ -std=c++11 -O2 -pthread main.cpp
+ ./a.out
v  0.000000 0.000000 0.000000
v  0.250000 0.125000 0.000000
v  0.156250 0.437500 0.000000
v  -0.125000 0.375000 0.000000
v  0.250000 0.125000 0.000000
v  0.500000 0.250000 0.000000
v  0.437500 0.500000 0.000000
v  0.156250 0.437500 0.000000
v  0.156250 0.437500 0.000000
v  0.437500 0.500000 0.000000
v  0.375000 0.750000 0.000000
v  0.062500 0.750000 0.000000
v  -0.125000 0.375000 0.000000
v  0.156250 0.437500 0.000000
v  0.062500 0.750000 0.000000
v  -0.250000 0.750000 0.000000
v  0.500000 0.250000 0.000000
v  0.750000 0.375000 0.000000
v  0.718750 0.562500 0.000000
v  0.437500 0.500000 0.000000
v  0.750000 0.375000 0.000000
v  1.000000 0.500000 0.000000
v  1.000000 0.625000 0.000000
v  0.718750 0.562500 0.000000
v  0.718750 0.562500 0.000000
v  1.000000 0.625000 0.000000
v  1.000000 0.750000 0.000000
v  0.687500 0.750000 0.000000
v  0.437500 0.500000 0.000000
v  0.718750 0.562500 0.000000
v  0.687500 0.750000 0.000000
v  0.375000 0.750000 0.000000
v  0.375000 0.750000 0.000000
v  0.687500 0.750000 0.000000
v  0.656250 0.937500 0.000000
v  0.312500 1.000000 0.000000
v  0.687500 0.750000 0.000000
v  1.000000 0.750000 0.000000
v  1.000000 0.875000 0.000000
v  0.656250 0.937500 0.000000
v  0.656250 0.937500 0.000000
v  1.000000 0.875000 0.000000
v  1.000000 1.000000 0.000000
v  0.625000 1.125000 0.000000
v  0.312500 1.000000 0.000000
v  0.656250 0.937500 0.000000
v  0.625000 1.125000 0.000000
v  0.250000 1.250000 0.000000
v  -0.250000 0.750000 0.000000
v  0.062500 0.750000 0.000000
v  -0.031250 1.062500 0.000000
v  -0.375000 1.125000 0.000000
v  0.062500 0.750000 0.000000
v  0.375000 0.750000 0.000000
v  0.312500 1.000000 0.000000
v  -0.031250 1.062500 0.000000
v  -0.031250 1.062500 0.000000
v  0.312500 1.000000 0.000000
v  0.250000 1.250000 0.000000
v  -0.125000 1.375000 0.000000
v  -0.375000 1.125000 0.000000
v  -0.031250 1.062500 0.000000
v  -0.125000 1.375000 0.000000
v  -0.500000 1.500000 0.000000


f 1 2 3 4
f 5 6 7 8
f 9 10 11 12
f 13 14 15 16
f 17 18 19 20
f 21 22 23 24
f 25 26 27 28
f 29 30 31 32
f 33 34 35 36
f 37 38 39 40
f 41 42 43 44
f 45 46 47 48
f 49 50 51 52
f 53 54 55 56
f 57 58 59 60
f 61 62 63 64