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/*
OneLoneCoder.com - Programming Balls! #1 Circle Vs Circle Collisions
"..it's just balls bangin' together init..." - @Javidx9
License
~~~~~~~
One Lone Coder Console Game Engine Copyright (C) 2018 Javidx9
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; See license for details.
Original works located at:
https://www.github.com/onelonecoder
https://www.onelonecoder.com
https://www.youtube.com/javidx9
GNU GPLv3
https://github.com/OneLoneCoder/videos/blob/master/LICENSE
From Javidx9 :)
~~~~~~~~~~~~~~~
Hello! Ultimately I don't care what you use this for. It's intended to be
educational, and perhaps to the oddly minded - a little bit of fun.
Please hack this, change it and use it in any way you see fit. You acknowledge
that I am not responsible for anything bad that happens as a result of
your actions. However this code is protected by GNU GPLv3, see the license in the
github repo. This means you must attribute me if you use it. You can view this
license here: https://github.com/OneLoneCoder/videos/blob/master/LICENSE
Cheers!
Background
~~~~~~~~~~
Collision detection engines can get quite complicated. This program shows the interactions
between circular objects of different sizes and masses. Use Left mouse button to select
and drag a ball to examin static collisions, and use Right mouse button to apply velocity
to the balls as if using a pool/snooker/billiards cue.
Author
~~~~~~
Twitter: @javidx9
Blog: www.onelonecoder.com
Video:
~~~~~~
Part #1 https://youtu.be/LPzyNOHY3A4
Last Updated: 21/01/2017
*/
#include <iostream>
#include <string>
using namespace std;
#include "olcConsoleGameEngine.h"
struct sBall
{
float px, py;
float vx, vy;
float ax, ay;
float radius;
float mass;
int id;
};
class CirclePhysics : public olcConsoleGameEngine
{
public:
CirclePhysics()
{
m_sAppName = L"Circle Physics";
}
private:
vector<pair<float, float>> modelCircle;
vector<sBall> vecBalls;
sBall *pSelectedBall = nullptr;
// Adds a ball to the vector
void AddBall(float x, float y, float r = 5.0f)
{
sBall b;
b.px = x; b.py = y;
b.vx = 0; b.vy = 0;
b.ax = 0; b.ay = 0;
b.radius = r;
b.mass = r * 10.0f;
b.id = vecBalls.size();
vecBalls.emplace_back(b);
}
public:
bool OnUserCreate()
{
// Define Circle Model
modelCircle.push_back({ 0.0f, 0.0f });
int nPoints = 20;
for (int i = 0; i < nPoints; i++)
modelCircle.push_back({ cosf(i / (float)(nPoints - 1) * 2.0f * 3.14159f) , sinf(i / (float)(nPoints - 1) * 2.0f * 3.14159f) });
float fDefaultRad = 8.0f;
//AddBall(ScreenWidth() * 0.25f, ScreenHeight() * 0.5f, fDefaultRad);
//AddBall(ScreenWidth() * 0.75f, ScreenHeight() * 0.5f, fDefaultRad);
// Add 10 Random Balls
for (int i = 0; i <10; i++)
AddBall(rand() % ScreenWidth(), rand() % ScreenHeight(), rand() % 16 + 2);
return true;
}
bool OnUserUpdate(float fElapsedTime)
{
auto DoCirclesOverlap = [](float x1, float y1, float r1, float x2, float y2, float r2)
{
return fabs((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2)) <= (r1 + r2)*(r1 + r2);
};
auto IsPointInCircle = [](float x1, float y1, float r1, float px, float py)
{
return fabs((x1 - px)*(x1 - px) + (y1 - py)*(y1 - py)) < (r1 * r1);
};
if (m_mouse[0].bPressed || m_mouse[1].bPressed)
{
pSelectedBall = nullptr;
for (auto &ball : vecBalls)
{
if (IsPointInCircle(ball.px, ball.py, ball.radius, m_mousePosX, m_mousePosY))
{
pSelectedBall = &ball;
break;
}
}
}
if (m_mouse[0].bHeld)
{
if (pSelectedBall != nullptr)
{
pSelectedBall->px = m_mousePosX;
pSelectedBall->py = m_mousePosY;
}
}
if (m_mouse[0].bReleased)
{
pSelectedBall = nullptr;
}
if (m_mouse[1].bReleased)
{
if (pSelectedBall != nullptr)
{
// Apply velocity
pSelectedBall->vx = 5.0f * ((pSelectedBall->px) - (float)m_mousePosX);
pSelectedBall->vy = 5.0f * ((pSelectedBall->py) - (float)m_mousePosY);
}
pSelectedBall = nullptr;
}
vector<pair<sBall*, sBall*>> vecCollidingPairs;
// Update Ball Positions
for (auto &ball : vecBalls)
{
// Add Drag to emulate rolling friction
ball.ax = -ball.vx * 0.8f;
ball.ay = -ball.vy * 0.8f;
// Update ball physics
ball.vx += ball.ax * fElapsedTime;
ball.vy += ball.ay * fElapsedTime;
ball.px += ball.vx * fElapsedTime;
ball.py += ball.vy * fElapsedTime;
// Wrap the balls around screen
if (ball.px < 0) ball.px += (float)ScreenWidth();
if (ball.px >= ScreenWidth()) ball.px -= (float)ScreenWidth();
if (ball.py < 0) ball.py += (float)ScreenHeight();
if (ball.py >= ScreenHeight()) ball.py -= (float)ScreenHeight();
// Clamp velocity near zero
if (fabs(ball.vx*ball.vx + ball.vy*ball.vy) < 0.01f)
{
ball.vx = 0;
ball.vy = 0;
}
}
// Static collisions, i.e. overlap
for (auto &ball : vecBalls)
{
for (auto &target : vecBalls)
{
if (ball.id != target.id)
{
if (DoCirclesOverlap(ball.px, ball.py, ball.radius, target.px, target.py, target.radius))
{
// Collision has occured
vecCollidingPairs.push_back({ &ball, &target });
// Distance between ball centers
float fDistance = sqrtf((ball.px - target.px)*(ball.px - target.px) + (ball.py - target.py)*(ball.py - target.py));
// Calculate displacement required
float fOverlap = 0.5f * (fDistance - ball.radius - target.radius);
// Displace Current Ball away from collision
ball.px -= fOverlap * (ball.px - target.px) / fDistance;
ball.py -= fOverlap * (ball.py - target.py) / fDistance;
// Displace Target Ball away from collision
target.px += fOverlap * (ball.px - target.px) / fDistance;
target.py += fOverlap * (ball.py - target.py) / fDistance;
}
}
}
}
// Now work out dynamic collisions
for (auto c : vecCollidingPairs)
{
sBall *b1 = c.first;
sBall *b2 = c.second;
// Distance between balls
float fDistance = sqrtf((b1->px - b2->px)*(b1->px - b2->px) + (b1->py - b2->py)*(b1->py - b2->py));
// Normal
float nx = (b2->px - b1->px) / fDistance;
float ny = (b2->py - b1->py) / fDistance;
// Tangent
float tx = -ny;
float ty = nx;
// Dot Product Tangent
float dpTan1 = b1->vx * tx + b1->vy * ty;
float dpTan2 = b2->vx * tx + b2->vy * ty;
// Dot Product Normal
float dpNorm1 = b1->vx * nx + b1->vy * ny;
float dpNorm2 = b2->vx * nx + b2->vy * ny;
// Conservation of momentum in 1D
float m1 = (dpNorm1 * (b1->mass - b2->mass) + 2.0f * b2->mass * dpNorm2) / (b1->mass + b2->mass);
float m2 = (dpNorm2 * (b2->mass - b1->mass) + 2.0f * b1->mass * dpNorm1) / (b1->mass + b2->mass);
// Update ball velocities
b1->vx = tx * dpTan1 + nx * m1;
b1->vy = ty * dpTan1 + ny * m1;
b2->vx = tx * dpTan2 + nx * m2;
b2->vy = ty * dpTan2 + ny * m2;
// Wikipedia Version - Maths is smarter but same
//float kx = (b1->vx - b2->vx);
//float ky = (b1->vy - b2->vy);
//float p = 2.0 * (nx * kx + ny * ky) / (b1->mass + b2->mass);
//b1->vx = b1->vx - p * b2->mass * nx;
//b1->vy = b1->vy - p * b2->mass * ny;
//b2->vx = b2->vx + p * b1->mass * nx;
//b2->vy = b2->vy + p * b1->mass * ny;
}
// Clear Screen
Fill(0, 0, ScreenWidth(), ScreenHeight(), ' ');
// Draw Balls
for (auto ball : vecBalls)
DrawWireFrameModel(modelCircle, ball.px, ball.py, atan2f(ball.vy, ball.vx), ball.radius, FG_WHITE);
// Draw static collisions
for (auto c : vecCollidingPairs)
DrawLine(c.first->px, c.first->py, c.second->px, c.second->py, PIXEL_SOLID, FG_RED);
// Draw Cue
if (pSelectedBall != nullptr)
DrawLine(pSelectedBall->px, pSelectedBall->py, m_mousePosX, m_mousePosY, PIXEL_SOLID, FG_BLUE);
return true;
}
};
int main()
{
CirclePhysics game;
if (game.ConstructConsole(160, 120, 8, 8))
game.Start();
else
wcout << L"Could not construct console" << endl;
return 0;
};