physics_engine/src/demo/ballistics.cpp

#include "math/float_types.hpp"
#include "math/transform.hpp"

#include "platform/graphics_primitive.hpp"
#include "platform/font.hpp"

#include "physics/particle.hpp"

#include "demo/ballistics.hpp"

namespace demo {

  void ballistics::projectile::draw(ta_parameter_writer& writer, const mat4x4& trans)
  {
    const vec3 color(1.0, 1.0, 1.0);
    draw_cube(writer, trans * translate(particle.position) * scale(1.f), color);
  }

  void ballistics::init()
  {
    current_projectile_type = projectile_type::ARTILLERY;

    for (int i = 0; i < max_projectiles; i++) {
      projectiles[i].type = projectile_type::NONE;
    }
  }

  void ballistics::a()
  {
    projectile * projectile;

    int i;
    for (i = 0; i < max_projectiles; i++) {
      projectile = &projectiles[i];
      if (projectile->type == projectile_type::NONE)
        break;
    }

    if (i >= max_projectiles)
      return; // too many projectiles

    switch (current_projectile_type) {
    case projectile_type::PISTOL:
      projectile->particle.inverse_mass = 1.0f / 2.0f;
      projectile->particle.velocity = vec3(0.0f, 0.0f, 35.0f);
      projectile->particle.acceleration = vec3(0.0f, -1.0f, 0.0f);
      projectile->particle.damping = 0.99f;
      break;
    case projectile_type::ARTILLERY:
      projectile->particle.inverse_mass = 1.0f / 1.0f;
      projectile->particle.velocity = vec3(0.0f, 30.0f, 40.0f);
      projectile->particle.acceleration = vec3(0.0f, -20.0f, 0.0f);
      projectile->particle.damping = 0.99f;
      break;
    case projectile_type::FIREBALL:
      projectile->particle.inverse_mass = 1.0f / 10.0f;
      projectile->particle.velocity = vec3(0.0f, 0.0f, 10.0f);
      projectile->particle.acceleration = vec3(0.0f, 0.6f, 0.0f);
      projectile->particle.damping = 0.99f;
      break;
    case projectile_type::LASER:
      projectile->particle.inverse_mass = 1.0f / 0.1f;
      projectile->particle.velocity = vec3(0.0f, 0.0f, 100.0f);
      projectile->particle.acceleration = vec3(0.0f, 0.0f, 0.0f);
      projectile->particle.damping = 0.99f;
      break;
    default:
      break;
    }

    projectile->particle.position = vec3(0.0f, 1.5f, 0.0f);
    projectile->start_time = tick;
    projectile->type = current_projectile_type;
    //projectile->particle.clear_accumulator(); FIXME
    projectile->particle.force_accum = vec3(0, 0, 0);
  }

  void ballistics::x()
  {
    switch (current_projectile_type) {
    default: [[fallthrough]];
    case projectile_type::PISTOL:    current_projectile_type = projectile_type::ARTILLERY; break;
    case projectile_type::ARTILLERY: current_projectile_type = projectile_type::FIREBALL;  break;
    case projectile_type::FIREBALL:  current_projectile_type = projectile_type::LASER;     break;
    case projectile_type::LASER:     current_projectile_type = projectile_type::PISTOL;    break;
    }
  }

  void ballistics::update()
  {
    float duration = 1.0f / 60.0f;
    tick += 1;

    for (int i = 0; i < max_projectiles; i++) {
      projectile * projectile = &projectiles[i];
      if (projectile->type == projectile_type::NONE)
        continue;

      projectile->particle.integrate(duration);

      if (projectile->particle.position.z > 200.0f ||
          projectile->particle.position.y < 0.0f ||
          projectile->start_time < tick - 600) {
        projectile->type = projectile_type::NONE;
      }
    }
  }

  void ballistics::draw_hud(ta_parameter_writer& writer)
  {
    const int title_length = 16;
    const int title_width_2 = (font::ter_u12n.hori_advance * title_length) >> 1;
    const int framebuffer_width_2 = framebuffer::framebuffer.px_width >> 1;
    const int x = framebuffer_width_2 - title_width_2;
    vec3 center_p = vec3(x, 5, 10);

    font::ter_u12n.global(writer);
    font::ter_u12n.draw_string(writer, center_p, "demo: ballistics", 0xffffffff);

    const char * label;
    switch (current_projectile_type) {
    default: [[fallthrough]];
    case projectile_type::PISTOL:    label = "pistol";    break;
    case projectile_type::ARTILLERY: label = "artillery"; break;
    case projectile_type::FIREBALL:  label = "fireball";  break;
    case projectile_type::LASER:     label = "laser";     break;
    }

    vec3 p(5, 10, 10);
    font::ter_u12n.draw_string(writer, p, "projectile_type:", 0xffffffff);
    p.x += font::ter_u12n.hori_advance * 17;
    font::ter_u12n.draw_string(writer, p, label, 0xffffffff);
  }

  void ballistics::draw(ta_parameter_writer& writer, const mat4x4& trans)
  {
    // punch through
    draw_hud(writer);

    writer.append<ta_global_parameter::end_of_list>() =
      ta_global_parameter::end_of_list(para_control::para_type::end_of_list);

    // opaque

    draw_axis(writer, trans * scale(5.f));

    draw_grid(writer, trans * translate(vec3(0, 0, 50)) * scale(vec3(20, 10, 100)));

    for (int i = 0; i < max_projectiles; i++) {
      projectile * projectile = &projectiles[i];
      if (projectile->type == projectile_type::NONE)
        continue;

      projectile->draw(writer, trans);
    }

    writer.append<ta_global_parameter::end_of_list>() =
      ta_global_parameter::end_of_list(para_control::para_type::end_of_list);
  }
}