Line data    Source code

       1              : /*
       2              :  * Copyright (C) 2025 aeml
       3              :  *
       4              :  * This program is free software: you can redistribute it and/or modify
       5              :  * it under the terms of the GNU General Public License as published by
       6              :  * the Free Software Foundation, either version 3 of the License, or
       7              :  * (at your option) any later version.
       8              :  *
       9              :  * This program is distributed in the hope that it will be useful,
      10              :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      11              :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12              :  * GNU General Public License for more details.
      13              :  *
      14              :  * You should have received a copy of the GNU General Public License
      15              :  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
      16              :  */
      17              : 
      18              : #pragma once
      19              : 
      20              : #include <algorithm>
      21              : #include <cstdint>
      22              : 
      23              : namespace physics
      24              : {
      25              :     struct TransformComponent
      26              :     {
      27              :         float x{0.0f};
      28              :         float y{0.0f};
      29              :         float rotation{0.0f};
      30              :     };
      31              : 
      32              :     struct RigidBodyComponent
      33              :     {
      34              :         float vx{0.0f};
      35              :         float vy{0.0f};
      36              :         float lastX{0.0f}; // For PBD
      37              :         float lastY{0.0f}; // For PBD
      38              :         float lastAngle{0.0f};
      39              :         float mass{1.0f};
      40              :         float invMass{1.0f}; // 1.0 / mass, 0.0 for static bodies
      41              :         float inertia{1.0f};
      42              :         float invInertia{1.0f};
      43              :         float restitution{0.5f}; // Bounciness [0, 1]
      44              :         float friction{0.5f}; // Friction coefficient [0, 1]
      45              :         float angularVelocity{0.0f};
      46              :         float torque{0.0f};
      47              :         float angularFriction{0.5f};
      48              :         float angularDrag{0.0f};
      49              :     };
      50              : 
      51              :     // Simple environment-wide forces for weather-like simulations.
      52              :     struct EnvironmentForces
      53              :     {
      54              :         float gravityY{-9.81f}; // downward acceleration
      55              :         float windX{0.0f};      // horizontal wind
      56              :         float windY{0.0f};      // vertical wind / updrafts
      57              :         float drag{0.0f};       // linear drag coefficient
      58              :     };
      59              : 
      60              :     struct DistanceJointComponent
      61              :     {
      62              :         std::uint32_t entityA;
      63              :         std::uint32_t entityB;
      64              :         float targetDistance;
      65              :         float compliance{0.0f}; // 0 = rigid, >0 = soft (inverse stiffness)
      66              :     };
      67              : 
      68              :     // Axis-aligned bounding box for simple collision tests.
      69              :     struct AABBComponent
      70              :     {
      71              :         float minX{0.0f};
      72              :         float minY{0.0f};
      73              :         float maxX{0.0f};
      74              :         float maxY{0.0f};
      75              :     };
      76              : 
      77              :     struct CircleColliderComponent
      78              :     {
      79              :         float radius{1.0f};
      80              :         float offsetX{0.0f};
      81              :         float offsetY{0.0f};
      82              :     };
      83              : 
      84         1908 :     inline void ConfigureCircleInertia(RigidBodyComponent& body, float radius)
      85              :     {
      86         1908 :         if (body.mass <= 0.0f || radius <= 0.0f)
      87              :         {
      88            0 :             body.inertia = 0.0f;
      89            0 :             body.invInertia = 0.0f;
      90            0 :             return;
      91              :         }
      92         1908 :         const float r = radius;
      93         1908 :         body.inertia = 0.5f * body.mass * r * r;
      94         1908 :         body.invInertia = body.inertia > 0.0f ? 1.0f / body.inertia : 0.0f;
      95              :     }
      96              : 
      97          324 :     inline void ConfigureBoxInertia(RigidBodyComponent& body, float width, float height)
      98              :     {
      99          324 :         if (body.mass <= 0.0f)
     100              :         {
     101            0 :             body.inertia = 0.0f;
     102            0 :             body.invInertia = 0.0f;
     103            0 :             return;
     104              :         }
     105          324 :         const float w = width;
     106          324 :         const float h = height;
     107          324 :         body.inertia = (body.mass / 12.0f) * (w * w + h * h);
     108          324 :         body.invInertia = body.inertia > 0.0f ? 1.0f / body.inertia : 0.0f;
     109              :     }
     110              : }