c++ 게임만들기 연습문제 3.3

* 인프런에 있는 "홍정모의 게임 만들기 연습 문제 패키지" 강의를 바탕으로 작성된 글입니다.

 

1. 3개 이상의 물체 테스트 해보기.

#include "Game2D.h"
#include "RandomNumberGenerator.h"
#include "RigidCircle.h"
#include <vector>
#include <memory>

namespace shyplants
{
	class Example : public Game2D
	{	
	public:
		RigidCircle rb[3];

		Example()
			: Game2D()
		{
			reset();
		}

		void reset()
		{
			// Initial position and velocity
			rb[0].pos = vec2(0.0f, 0.5f);
			rb[0].vel = vec2(0.0f, 0.0f);
			rb[0].color = Colors::hotpink;
			rb[0].radius = 0.03f;
			rb[0].mass = 1.0f;
			rb[0].fixed = true;

			rb[1].pos = vec2(0.3f, 0.3f);
			rb[1].vel = vec2(0.0f, 0.0f);
			rb[1].color = Colors::yellow;
			rb[1].radius = 0.03f;
			rb[1].mass = rb[0].mass * std::pow(rb[1].radius / rb[0].radius, 2.0f);
			rb[1].fixed = false;

			rb[2].pos = vec2(0.1f, 0.2f);
			rb[2].vel = vec2(0.0f, 0.0f);
			rb[2].color = Colors::yellow;
			rb[2].radius = 0.03f;
			rb[2].mass = rb[0].mass * std::pow(rb[2].radius / rb[0].radius, 2.0f);
			rb[1].fixed = false;
		}

		void drawWall()
		{
			setLineWidth(5.0f);
			drawLine(Colors::blue, { -1.0f, -1.0f }, Colors::blue, { 1.0f, -1.0f });
			drawLine(Colors::blue, { 1.0f, -1.0f }, Colors::blue, { 1.0f, 1.0f });
			drawLine(Colors::blue, { -1.0f, -1.0f }, Colors::blue, { -1.0f, 1.0f });
		}

		void update() override
		{
			const float dt = getTimeStep() * 0.4f;
			const float epsilon = 0.5f;

			// coefficients
			const vec2 gravity(0.0f, -9.8f);
			const float l0 = 0.5f;		
			const float coeff_k = 100.0f;
			const float coeff_d = 10.0f;

			// update rb1 ~ rb2 (Note: rb0 is fixed)
			for (int i = 1; i < 3; ++i) 
			{
				const auto distance = (rb[i].pos - rb[i-1].pos).getMagnitude();
				const auto direction = (rb[i].pos - rb[i-1].pos) / distance;

				// compute stiffness force
				const auto spring_force = direction * -(distance - l0) * coeff_k;
				// compute damping force
				const auto damping_force = direction * -(rb[i].vel - rb[i-1].vel).getDotProduct(direction) * coeff_d;

				const auto accel = gravity + (spring_force + damping_force) / rb[i].mass;


				rb[i].vel += accel * dt;
				if (!rb[i - 1].fixed) rb[i - 1].vel -= accel * dt;
			}

			for (int i = 1; i < 3; ++i)
			{
				rb[1].pos += rb[1].vel * dt;
				rb[2].pos += rb[2].vel * dt;
			}

			// draw
			drawWall();

			// spring
			for (int i = 1; i < 3; ++i) {
				drawLine(Colors::red, rb[i-1].pos, Colors::red, rb[i].pos);
			}

			// mass points
			for (int i = 0; i < 3; ++i) {
				rb[i].draw();
			}
			
			// reset button
			if (isKeyPressedAndReleased(GLFW_KEY_R)) reset();
		}
	};
}

 

 

2. 영상 후반부 옷감 테스트 해보기.

#include "Game2D.h"
#include "RandomNumberGenerator.h"
#include "RigidCircle.h"
#include <vector>
#include <memory>

namespace shyplants
{
	class Example : public Game2D
	{	
	public:
		std::vector<RigidCircle*> rCircles;
		int row = 6, col = 6;

		Example()
			: Game2D()
		{
			reset();
		}

		void reset()
		{
			rCircles.clear();
			
			// Initial position and velocity
			vec2 pos = vec2(-0.5f, 0.5f);
			vec2 vel = vec2(0, 0);
			float radius = 0.03f;
			float mass = 1.0f;

			for (int r = 0; r < row; ++r) {
				for (int c = 0; c < col; ++c) {
					vec2 cur_pos = pos + vec2(1.0f / (col - 1) * c, -1.0f / (row - 1) * r);
					bool fixed = (r == 0 && (c == 0 || c == col - 1));
					RGB color = fixed ? Colors::gold : Colors::blue;

					rCircles.emplace_back(new RigidCircle(cur_pos, vel, color, radius, mass, fixed));
				}
			}
		}

		void drawWall()
		{
			setLineWidth(5.0f);
			drawLine(Colors::blue, { -1.0f, -1.0f }, Colors::blue, { 1.0f, -1.0f });
			drawLine(Colors::blue, { 1.0f, -1.0f }, Colors::blue, { 1.0f, 1.0f });
			drawLine(Colors::blue, { -1.0f, -1.0f }, Colors::blue, { -1.0f, 1.0f });
		}

		bool OOB(int y, int x) {
			return y < 0 || y >= row || x < 0 || x >= col;
		}

		int min(int a, int b) {
			return a < b ? a : b;
		}

		int max(int a, int b) {
			return a > b ? a : b;
		}

		void update() override
		{
			const float dt = getTimeStep() * 0.4f;
			const float epsilon = 0.5f;

			// coefficients
			const vec2 gravity(0.0f, -9.8f);
			const float l0 = 1.0f / (max(row, col) - 1) / 1.2f;
			const float coeff_k = 150.0f;
			const float coeff_d = 10.0f;
			const float coef_res = 0.8f;       // coefficient of restitution
			const float coef_friction = 0.99f; // friction (not physical)

			// update rCircle
			const int dy[] = { -1, -1, -1, 0, 0 };
			const int dx[] = { -1, 0, 1, -1, 1 };
			
			for (int r = 0; r < row; ++r) {
				for (int c = 0; c < col; ++c) {
					const int cur_pos = r * col + c;
					vec2 tot_spring_force = vec2(0, 0);
					vec2 tot_damping_force = vec2(0, 0);

					for (int dir = 0; dir < 5; ++dir) {
						if (OOB(r + dy[dir], c + dx[dir])) continue;

						const int prev_pos = (r + dy[dir]) * col + (c + dx[dir]);

						const auto distance = (rCircles[cur_pos]->pos - rCircles[prev_pos]->pos).getMagnitude();
						const auto direction = (rCircles[cur_pos]->pos - rCircles[prev_pos]->pos) / distance;

						// compute stiffness force
						const auto spring_force = direction * -(distance - l0) * coeff_k;
						tot_spring_force += spring_force;
						// compute damping force
						const auto damping_force = direction * -(rCircles[cur_pos]->vel - rCircles[prev_pos]->vel).getDotProduct(direction) * coeff_d;
						tot_damping_force += damping_force;

						if (!rCircles[prev_pos]->fixed)
							rCircles[prev_pos]->vel -= (spring_force + damping_force) / rCircles[prev_pos]->mass * dt;
					}

					const auto accel = gravity + (tot_spring_force + tot_damping_force) / rCircles[cur_pos]->mass;
					if (!rCircles[cur_pos]->fixed)
						rCircles[cur_pos]->vel += accel * dt;
				}
			}

			for (auto& c : rCircles) if (!c->fixed) {
				c->pos += c->vel * dt;

				if (c->pos.y <= -1.0f + c->radius) // ground
				{
					c->pos.y = -1.0f + c->radius;

					if (c->vel.y <= 0.0f)
						c->vel.y *= -1.0f * coef_res;

					c->vel.x *= coef_friction;
				}
			}
		
			// draw
			drawWall();

			// spring
			for (int r = 0; r < row; ++r) {
				for (int c = 0; c < col; ++c) {
					if (r == row - 1 && c == col - 1) break;

					if(c == col-1 && r < row-1)
						drawLine(Colors::red, rCircles[r*col + c]->pos, Colors::red, rCircles[r*col + col + c]->pos);
					else if(r == row-1 && c < col-1)
						drawLine(Colors::red, rCircles[r*col + c]->pos, Colors::red, rCircles[r*col + c + 1]->pos);
					else {
						drawLine(Colors::red, rCircles[r*col + c]->pos, Colors::red, rCircles[r*col + c + 1]->pos);
						drawLine(Colors::red, rCircles[r*col + c]->pos, Colors::red, rCircles[r*col + col + c + 1]->pos);
						drawLine(Colors::red, rCircles[r*col + c + 1]->pos, Colors::red, rCircles[r*col + col + c]->pos);
						drawLine(Colors::red, rCircles[r*col + c]->pos, Colors::red, rCircles[r*col + col + c]->pos);
					}
				}
			}
			
			// mass points
			for (auto& c : rCircles) {
				c->draw();
			}
			
			// reset button
			if (isKeyPressedAndReleased(GLFW_KEY_R)) reset();
		}
	};
}