jumpartifact.com_demo_0/src/3d_helpers.cc

#include "3d_helpers.h"

// standard library includes
#include <cmath>

// third party includes
#include <raymath.h>

// local includes
#include "ems.h"

Matrix get_identity_matrix() {
  return Matrix{1.0F, 0.0F, 0.0F, 0.0F, 0.0F, 1.0F, 0.0F, 0.0F,
                0.0F, 0.0F, 1.0F, 0.0F, 0.0F, 0.0F, 0.0F, 1.0F};
}

// Rotation is
// cos, -sin,
// sin, cos
// probably?
//
// About z-axis:
// cos, -sin, 0, 0,
// sin,  cos, 0, 0,
// 0,    0,   1, 0,
// 0,    0,   0, 1

Matrix get_rotation_matrix_about_z(float radians) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{std::cos(radians),
                -std::sin(radians),
                0.0F,
                0.0F,
                std::sin(radians),
                std::cos(radians),
                0.0F,
                0.0F,
                0.0F,
                0.0F,
                1.0F,
                0.0F,
                0.0F,
                0.0F,
                0.0F,
                1.0F};
}

// About y-axis
//  cos, 0, sin, 0,
//  0,   1, 0,   0,
// -sin, 0, cos, 0,
//  0,   0, 0,   1

Matrix get_rotation_matrix_about_y(float radians) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{std::cos(radians),
                0.0F,
                std::sin(radians),
                0.0F,
                0.0F,
                1.0F,
                0.0F,
                0.0F,
                -std::sin(radians),
                0.0F,
                std::cos(radians),
                0.0F,
                0.0F,
                0.0F,
                0.0F,
                1.0F};
}

// About x-axis
// 1, 0,    0,   0
// 0, cos, -sin, 0
// 0, sin,  cos, 0
// 0, 0,    0,   1

Matrix get_rotation_matrix_about_x(float radians) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{1.0F,
                0.0F,
                0.0F,
                0.0F,
                0.0F,
                std::cos(radians),
                -std::sin(radians),
                0.0F,
                0.0F,
                std::sin(radians),
                std::cos(radians),
                0.0F,
                0.0F,
                0.0F,
                0.0F,
                1.0F};
}

Matrix translate_matrix_x(float distance) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{1.0F, 0.0F, 0.0F, distance, 0.0F, 1.0F, 0.0F, 0.0F,
                0.0F, 0.0F, 1.0F, 0.0F,     0.0F, 0.0F, 0.0F, 1.0F};
}

Matrix translate_matrix_y(float distance) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{1.0F, 0.0F, 0.0F, 0.0F, 0.0F, 1.0F, 0.0F, distance,
                0.0F, 0.0F, 1.0F, 0.0F, 0.0F, 0.0F, 0.0F, 1.0F};
}

Matrix translate_matrix_z(float distance) {
  // OpenGL is column-major but testing shows that not transposing works.
  return Matrix{1.0F, 0.0F, 0.0F, 0.0F,     0.0F, 1.0F, 0.0F, 0.0F,
                0.0F, 0.0F, 1.0F, distance, 0.0F, 0.0F, 0.0F, 1.0F};
}

Matrix translate_matrix_xyz(float x, float y, float z) {
  return Matrix{1.0F, 0.0F, 0.0F, x, 0.0F, 1.0F, 0.0F, y,
                0.0F, 0.0F, 1.0F, z, 0.0F, 0.0F, 0.0F, 1.0F};
}

Matrix scale_matrix_xyz(float x, float y, float z) {
  return Matrix{x,    0.0F, 0.0F, 0.0F, 0.0F, y,    0.0F, 0.0F,
                0.0F, 0.0F, z,    0.0F, 0.0F, 0.0F, 0.0F, 1.0F};
}

Matrix operator*(const Matrix &a, const Matrix &b) {
  return MatrixMultiply(a, b);
}

bool ray_to_xz_plane(const Ray &ray, float &x_out, float &z_out) {
  if (FloatEquals(ray.direction.y, 0.0F)) {
    return false;
  }
  // y = 0 -> amount to set ray.dir to set ray.pos to zero
  // 0 = py + dy * amount
  // amount = -py / dy
  float amount = -ray.position.y / ray.direction.y;

  // x = px + dx * amount
  x_out = ray.position.x + ray.direction.x * amount;

  // z = pz + dz * amount
  z_out = ray.position.z + ray.direction.z * amount;

  return true;
}

std::optional<Vector3> ray_to_plane(const Ray &ray, const Ray &plane) {
  // Ray dir and plane normal.
  float rd_pn = Vector3DotProduct(ray.direction, plane.direction);
  if (FloatEquals(rd_pn, 0.0F)) {
    return std::nullopt;
  }

  float amount = (Vector3DotProduct(plane.position, plane.direction) -
                  Vector3DotProduct(ray.position, plane.direction)) /
                 rd_pn;

  // Negative amount means collision in opposite direction of ray.
  if (amount < 0.0F) {
    return std::nullopt;
  }

  // Amount * ray_dir + ray_pos == plane intersection.
  return Vector3{ray.position.x + ray.direction.x * amount,
                 ray.position.y + ray.direction.y * amount,
                 ray.position.z + ray.direction.z * amount};
}

Vector3 from_edge_to_sphere_random(Vector3 center, Vector3 point,
                                   float radius) {
  Vector3 to_center = center - point;
  Vector3 perpendicular = Vector3Normalize(Vector3Perpendicular(to_center));

  return Vector3Normalize(
      to_center + Vector3RotateByAxisAngle(perpendicular,
                                           Vector3Normalize(to_center),
                                           call_js_get_random() * PI * 2.0F) *
                      (call_js_get_random() * radius));
}

std::array<Vector3, 4> get_quad_from_start_end(Vector3 start, Vector3 end,
                                               Vector3 normal, float width) {
  std::array<Vector3, 4> quad;
  Vector3 start_to_end = Vector3Normalize(end - start);

  // Normalize just in case "normal" isn't actually a true normal.
  quad[0] = Vector3Normalize(Vector3CrossProduct(start_to_end, normal));
  quad[1] = start + quad[0] * (width / 2.0F);
  quad[2] = end + quad[0] * (width / 2.0F);
  quad[3] = end - quad[0] * (width / 2.0F);
  quad[0] = start - quad[0] * (width / 2.0F);

  return quad;
}

std::array<Vector3, 9> get_circle_facing_viewer(Vector3 pos, Vector3 normal,
                                                float radius) {
  std::array<Vector3, 9> vertices;

  vertices[0] = pos;

  // Normalize just in case the normal isn't a unit vector.
  normal = Vector3Normalize(normal);

  vertices[1] = Vector3Perpendicular(normal) * radius;
  vertices[2] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 1.0F / 8.0F) +
      pos;
  vertices[3] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 2.0F / 8.0F) +
      pos;
  vertices[4] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 3.0F / 8.0F) +
      pos;
  vertices[5] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 4.0F / 8.0F) +
      pos;
  vertices[6] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 5.0F / 8.0F) +
      pos;
  vertices[7] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 6.0F / 8.0F) +
      pos;
  vertices[8] =
      Vector3RotateByAxisAngle(vertices[1], normal, PI * 2.0F * 7.0F / 8.0F) +
      pos;
  vertices[1] = vertices[1] + pos;

  return vertices;
}

Vector3 operator+(Vector3 a, Vector3 b) {
  return Vector3{a.x + b.x, a.y + b.y, a.z + b.z};
}

Vector3 operator-(Vector3 a, Vector3 b) {
  return Vector3{a.x - b.x, a.y - b.y, a.z - b.z};
}

Vector3 operator*(Vector3 vec3, float factor) {
  return Vector3Scale(vec3, factor);
}

Vector3 operator*(Matrix mat, Vector3 vec3) {
  return Vector3Transform(vec3, mat);
}

Vector4 operator*(Vector4 a, Vector4 b) {
  return Vector4{a.x * b.x, a.y * b.y, a.z * b.z, a.w * b.w};
}