OpenSiv3D 実装会(6/24)で作ったサンプル１

main.cpp

//
// Siv3Dで3D
//

# include <Siv3D.hpp>
// ベクトル＆行列ライブラリ
// SOURCE https://glm.g-truc.net/0.9.8/index.html
# include "glm/glm.hpp"
# include "glm/gtc/matrix_transform.hpp"
# include "glm/gtx/transform.hpp"
# include "glm/gtx/string_cast.hpp"


void Main()
{
  const int window_width  = 960;
  const int window_height = 640;

  Window::Resize(window_width, window_height);

  glm::vec4 vertex[] {
    // TOP
    { -1, -1, -1, 1 },
    {  1, -1, -1, 1 },
    {  1, -1,  1, 1 },
    { -1, -1,  1, 1 },
    // BOTTOM
    { -1,  1, -1, 1 },
    { -1,  1,  1, 1 },
    {  1,  1,  1, 1 },
    {  1,  1, -1, 1 },
    // LEFT
    { -1, -1, -1, 1 },
    { -1, -1,  1, 1 },
    { -1,  1,  1, 1 },
    { -1,  1, -1, 1 },
    // RIGHT
    {  1, -1, -1, 1 },
    {  1,  1, -1, 1 },
    {  1,  1,  1, 1 },
    {  1, -1,  1, 1 },
    // FRONT
    { -1, -1,  1, 1 },
    {  1, -1,  1, 1 },
    {  1,  1,  1, 1 },
    { -1,  1,  1, 1 },
    // BACK
    { -1, -1, -1, 1 },
    { -1,  1, -1, 1 },
    {  1,  1, -1, 1 },
    {  1, -1, -1, 1 },
  };

  auto proj_matrix = glm::perspective(float(M_PI) * 60.0f / 180.0f, float(window_width) / float(window_height), 0.1f, 100.0f);
  auto view_matrix = glm::translate(glm::vec3(0, 0, -5.0));

  ColorF color[] = {
    { 0, 0, 1 },
    { 0, 1, 0 },
    { 0, 1, 1 },
    { 1, 0, 0 },
    { 1, 0, 1 },
    { 1, 1, 0 },
  };

  float yaw   = 0.0f;
  float pitch = 0.0f;

	while (System::Update())
	{
    auto model_matrix = glm::rotate(yaw, glm::vec3(0, 1, 0)) * glm::rotate(pitch, glm::vec3(1, 0, 0));
    yaw   += 0.01f;
    pitch += 0.006f;

    for (int i = 0; i < 6; ++i)
    {
      glm::vec2 p[4];
      glm::vec3 p3[4];
      for (int j = 0; j < 4; ++j)
      {
        // 簡易透視変換
        auto pos = view_matrix * model_matrix * vertex[i * 4 + j];
        p3[j] = pos;
        pos = proj_matrix * pos;
        pos = pos / pos.w;

        // 単位座標→表示画面座標
        glm::vec2 p2(pos.x * (window_width / 2), pos.y * (window_height / 2));
        p2 = p2 + glm::vec2(window_width / 2, window_height / 2);
        p[j] = p2;
      }

      // 表裏判定
      auto a = p[1] - p[0];
      auto b = p[2] - p[0];
      auto cross = a.x * b.y - b.x * a.y;
      if (cross > 0.0f)
      {
        auto v1 = p3[1] - p3[0];
        auto v2 = p3[2] - p3[0];
        auto cv = glm::normalize(glm::cross(v1, v2));
        auto dot = glm::dot(cv, glm::vec3(0, 0, 1));

        Quad(Vec2(p[0].x, p[0].y),
             Vec2(p[1].x, p[1].y),
             Vec2(p[2].x, p[2].y),
             Vec2(p[3].x, p[3].y)).draw(color[i] * dot);
      }
    }
	}
}