videos/OneLoneCoder_Splines1.cpp

/*
OneLoneCoder.com - Splines Part 1
"Bendy Wavy Curly" - @Javidx9

Disclaimer
~~~~~~~~~~
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. BUT, you acknowledge that I am not responsible for anything
bad that happens as a result of your actions. However, if good stuff happens, I
would appreciate a shout out, or at least give the blog some publicity for me.
Cheers!

Background
~~~~~~~~~~
Curvy things are always better. Splines are a nice way to approximate
curves and loops for games. This video is the first of two parts
demonstrating how Catmull-Rom splines can be implemented.

Use Z + X to select a point and move it with the arrow keys
Use A + S to move the agent around the spline loop

Author
~~~~~~
Twitter: @javidx9
Blog: www.onelonecoder.com

Video:
~~~~~~
https://youtu.be/9_aJGUTePYo

Last Updated: 06/08/2017
*/
#include <iostream>
#include <string>
using namespace std;

#include "olcConsoleGameEngine.h"

struct sPoint2D
{
	float x;
	float y;
};

struct sSpline
{
	vector<sPoint2D> points;

	sPoint2D GetSplinePoint(float t, bool bLooped = false)
	{
		int p0, p1, p2, p3;
		if (!bLooped)
		{
			p1 = (int)t + 1;
			p2 = p1 + 1;
			p3 = p2 + 1;
			p0 = p1 - 1;
		}
		else
		{
			p1 = (int)t;
			p2 = (p1 + 1) % points.size();
			p3 = (p2 + 1) % points.size();
			p0 = p1 >= 1 ? p1 - 1 : points.size() - 1;
		}

		t = t - (int)t;

		float tt = t * t;
		float ttt = tt * t;

		float q1 = -ttt + 2.0f*tt - t;
		float q2 = 3.0f*ttt - 5.0f*tt + 2.0f;
		float q3 = -3.0f*ttt + 4.0f*tt + t;
		float q4 = ttt - tt;

		float tx = 0.5f * (points[p0].x * q1 + points[p1].x * q2 + points[p2].x * q3 + points[p3].x * q4);
		float ty = 0.5f * (points[p0].y * q1 + points[p1].y * q2 + points[p2].y * q3 + points[p3].y * q4);

		return{ tx, ty };
	}

	sPoint2D GetSplineGradient(float t, bool bLooped = false)
	{
		int p0, p1, p2, p3;
		if (!bLooped)
		{
			p1 = (int)t + 1;
			p2 = p1 + 1;
			p3 = p2 + 1;
			p0 = p1 - 1;
		}
		else
		{
			p1 = (int)t;
			p2 = (p1 + 1) % points.size();
			p3 = (p2 + 1) % points.size();
			p0 = p1 >= 1 ? p1 - 1 : points.size() - 1;
		}

		t = t - (int)t;

		float tt = t * t;
		float ttt = tt * t;

		float q1 = -3.0f * tt + 4.0f*t - 1;
		float q2 = 9.0f*tt - 10.0f*t;
		float q3 = -9.0f*tt + 8.0f*t + 1.0f;
		float q4 = 3.0f*tt - 2.0f*t;

		float tx = 0.5f * (points[p0].x * q1 + points[p1].x * q2 + points[p2].x * q3 + points[p3].x * q4);
		float ty = 0.5f * (points[p0].y * q1 + points[p1].y * q2 + points[p2].y * q3 + points[p3].y * q4);

		return{ tx, ty };
	}
};

class OneLoneCoder_Splines : public olcConsoleGameEngine
{
public:
	OneLoneCoder_Splines()
	{
		m_sAppName = L"Splines";
	}

private:
	sSpline path;
	int nSelectedPoint = 0;
	float fMarker = 0.0f;

protected:
	// Called by olcConsoleGameEngine
	virtual bool OnUserCreate()
	{
		//path.points = { { 10, 41 },{ 40, 41 },{ 70, 41 },{ 100, 41 } };
		path.points = { { 10, 41 },{ 20, 41 },{ 30, 41 },{ 40, 41 },{ 50, 41 },{ 60, 41 },{ 70, 41 },{ 80, 41 },{ 90, 41 },{ 100, 41 } };
		return true;
	}

	// Called by olcConsoleGameEngine
	virtual bool OnUserUpdate(float fElapsedTime)
	{
		// Clear Screen
		Fill(0, 0, ScreenWidth(), ScreenHeight(), L' ');

		// Handle input
		if (m_keys[L'X'].bReleased)
		{
			nSelectedPoint++;
			if (nSelectedPoint >= path.points.size())
				nSelectedPoint = 0;
		}

		if (m_keys[L'Z'].bReleased)
		{
			nSelectedPoint--;
			if (nSelectedPoint < 0)
				nSelectedPoint = path.points.size() - 1;
		}

		if (m_keys[VK_LEFT].bHeld)
			path.points[nSelectedPoint].x -= 30.0f * fElapsedTime;

		if (m_keys[VK_RIGHT].bHeld)
			path.points[nSelectedPoint].x += 30.0f * fElapsedTime;

		if (m_keys[VK_UP].bHeld)
			path.points[nSelectedPoint].y -= 30.0f * fElapsedTime;

		if (m_keys[VK_DOWN].bHeld)
			path.points[nSelectedPoint].y += 30.0f * fElapsedTime;

		if (m_keys[L'A'].bHeld)
			fMarker -= 5.0f * fElapsedTime;

		if (m_keys[L'S'].bHeld)
			fMarker += 5.0f * fElapsedTime;

		if (fMarker >= (float)path.points.size())
			fMarker -= (float)path.points.size();

		if (fMarker < 0.0f)
			fMarker += (float)path.points.size();

		// Draw Spline
		for (float t = 0; t < (float)path.points.size(); t += 0.005f)
		{
			sPoint2D pos = path.GetSplinePoint(t, true);
			Draw(pos.x, pos.y);
		}

		// Draw Control Points
		for (int i = 0; i < path.points.size(); i++)
		{
			Fill(path.points[i].x - 1, path.points[i].y - 1, path.points[i].x + 2, path.points[i].y + 2, PIXEL_SOLID, FG_RED);
			DrawString(path.points[i].x, path.points[i].y, to_wstring(i));
		}

		// Highlight control point
		Fill(path.points[nSelectedPoint].x - 1, path.points[nSelectedPoint].y - 1, path.points[nSelectedPoint].x + 2, path.points[nSelectedPoint].y + 2, PIXEL_SOLID, FG_YELLOW);
		DrawString(path.points[nSelectedPoint].x, path.points[nSelectedPoint].y, to_wstring(nSelectedPoint));

		// Draw agent to demonstrate gradient
		sPoint2D p1 = path.GetSplinePoint(fMarker, true);
		sPoint2D g1 = path.GetSplineGradient(fMarker, true);
		float r = atan2(-g1.y, g1.x);
		DrawLine(5.0f * sin(r) + p1.x, 5.0f * cos(r) + p1.y, -5.0f * sin(r) + p1.x, -5.0f * cos(r) + p1.y, PIXEL_SOLID, FG_BLUE);
		return true;
	}
};

int main()
{
	OneLoneCoder_Splines demo;
	demo.ConstructConsole(160, 80, 10, 10);
	demo.Start();
	return 0;
}