olcPixelGameEngine/Videos/OneLoneCoder_PGE_SpriteTransforms.cpp

/*
	OneLoneCoder.com - 2D Sprite Affine Transformations
	"No more 90 degree movements" - @Javidx9


	Background
	~~~~~~~~~~
	The sophistication of 2D engines is enhanced when the programmer is
	able to rotate and scale sprites in a convenient manner. This program
	shows the basics of how affine transformations accomplish this.

	License (OLC-3)
	~~~~~~~~~~~~~~~

	Copyright 2018 OneLoneCoder.com

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	1. Redistributions or derivations of source code must retain the above
	copyright notice, this list of conditions and the following disclaimer.

	2. Redistributions or derivative works in binary form must reproduce
	the above copyright notice. This list of conditions and the following
	disclaimer must be reproduced in the documentation and/or other
	materials provided with the distribution.

	3. Neither the name of the copyright holder nor the names of its
	contributors may be used to endorse or promote products derived
	from this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	Links
	~~~~~
	YouTube:	https://www.youtube.com/javidx9
	Discord:	https://discord.gg/WhwHUMV
	Twitter:	https://www.twitter.com/javidx9
	Twitch:		https://www.twitch.tv/javidx9
	GitHub:		https://www.github.com/onelonecoder
	Patreon:	https://www.patreon.com/javidx9
	Homepage:	https://www.onelonecoder.com

	Relevant Videos
	~~~~~~~~~~~~~~~
	https://youtu.be/zxwLN2blwbQ

	Author
	~~~~~~
	David Barr, aka javidx9, <EFBFBD>OneLoneCoder 2018
*/


#define OLC_PGE_APPLICATION
#include "olcPixelGameEngine.h"

#include <algorithm>
#undef min
#undef max


class SpriteTransforms : public olc::PixelGameEngine
{
public:
	SpriteTransforms()
	{
		sAppName = "Sprite Transforms";
	}

private:
	olc::Sprite *sprCar;

	struct matrix3x3
	{
		float m[3][3];
	};

	void Identity(matrix3x3 &mat)
	{
		mat.m[0][0] = 1.0f; mat.m[1][0] = 0.0f; mat.m[2][0] = 0.0f;
		mat.m[0][1] = 0.0f; mat.m[1][1] = 1.0f; mat.m[2][1] = 0.0f;
		mat.m[0][2] = 0.0f; mat.m[1][2] = 0.0f; mat.m[2][2] = 1.0f;
	}

	void Translate(matrix3x3 &mat, float ox, float oy)
	{
		mat.m[0][0] = 1.0f; mat.m[1][0] = 0.0f; mat.m[2][0] = ox;
		mat.m[0][1] = 0.0f; mat.m[1][1] = 1.0f; mat.m[2][1] = oy;
		mat.m[0][2] = 0.0f;	mat.m[1][2] = 0.0f;	mat.m[2][2] = 1.0f;
	}

	void Rotate(matrix3x3 &mat, float fTheta)
	{
		mat.m[0][0] = cosf(fTheta);  mat.m[1][0] = sinf(fTheta); mat.m[2][0] = 0.0f;
		mat.m[0][1] = -sinf(fTheta); mat.m[1][1] = cosf(fTheta); mat.m[2][1] = 0.0f;
		mat.m[0][2] = 0.0f;			 mat.m[1][2] = 0.0f;		 mat.m[2][2] = 1.0f;
	}

	void Scale(matrix3x3 &mat, float sx, float sy)
	{
		mat.m[0][0] = sx;   mat.m[1][0] = 0.0f; mat.m[2][0] = 0.0f;
		mat.m[0][1] = 0.0f; mat.m[1][1] = sy;   mat.m[2][1] = 0.0f;
		mat.m[0][2] = 0.0f;	mat.m[1][2] = 0.0f;	mat.m[2][2] = 1.0f;
	}

	void Shear(matrix3x3 &mat, float sx, float sy)
	{	
		mat.m[0][0] = 1.0f; mat.m[1][0] = sx;   mat.m[2][0] = 0.0f;
		mat.m[0][1] = sy;   mat.m[1][1] = 1.0f; mat.m[2][1] = 0.0f;
		mat.m[0][2] = 0.0f;	mat.m[1][2] = 0.0f;	mat.m[2][2] = 1.0f;
	}

	void MatrixMultiply(matrix3x3 &matResult, matrix3x3 &matA, matrix3x3 &matB)
	{
		for (int c = 0; c < 3; c++)
		{
			for (int r = 0; r < 3; r++)
			{
				matResult.m[c][r] = matA.m[0][r] * matB.m[c][0] +
					                matA.m[1][r] * matB.m[c][1] +
					                matA.m[2][r] * matB.m[c][2];
			}
		}
	}

	void Forward(matrix3x3 &mat, float in_x, float in_y, float &out_x, float &out_y)
	{
		out_x = in_x * mat.m[0][0] + in_y * mat.m[1][0] + mat.m[2][0];
		out_y = in_x * mat.m[0][1] + in_y * mat.m[1][1] + mat.m[2][1];
	}

	void Invert(matrix3x3 &matIn, matrix3x3 &matOut)
	{
		float det = matIn.m[0][0] * (matIn.m[1][1] * matIn.m[2][2] - matIn.m[1][2] * matIn.m[2][1]) -
			matIn.m[1][0] * (matIn.m[0][1] * matIn.m[2][2] - matIn.m[2][1] * matIn.m[0][2]) +
			matIn.m[2][0] * (matIn.m[0][1] * matIn.m[1][2] - matIn.m[1][1] * matIn.m[0][2]);

		float idet = 1.0f / det;
		matOut.m[0][0] = (matIn.m[1][1] * matIn.m[2][2] - matIn.m[1][2] * matIn.m[2][1]) * idet;
		matOut.m[1][0] = (matIn.m[2][0] * matIn.m[1][2] - matIn.m[1][0] * matIn.m[2][2]) * idet;
		matOut.m[2][0] = (matIn.m[1][0] * matIn.m[2][1] - matIn.m[2][0] * matIn.m[1][1]) * idet;
		matOut.m[0][1] = (matIn.m[2][1] * matIn.m[0][2] - matIn.m[0][1] * matIn.m[2][2]) * idet;
		matOut.m[1][1] = (matIn.m[0][0] * matIn.m[2][2] - matIn.m[2][0] * matIn.m[0][2]) * idet;
		matOut.m[2][1] = (matIn.m[0][1] * matIn.m[2][0] - matIn.m[0][0] * matIn.m[2][1]) * idet;
		matOut.m[0][2] = (matIn.m[0][1] * matIn.m[1][2] - matIn.m[0][2] * matIn.m[1][1]) * idet;
		matOut.m[1][2] = (matIn.m[0][2] * matIn.m[1][0] - matIn.m[0][0] * matIn.m[1][2]) * idet;
		matOut.m[2][2] = (matIn.m[0][0] * matIn.m[1][1] - matIn.m[0][1] * matIn.m[1][0]) * idet;
	}


	float fRotate = 0.0f;

public:
	bool OnUserCreate() override
	{
		sprCar = new olc::Sprite("car_top1.png");

		return true;
	}

	bool OnUserUpdate(float fElapsedTime) override
	{
		
		if (GetKey(olc::Key::Z).bHeld) fRotate -= 2.0f * fElapsedTime;
		if (GetKey(olc::Key::X).bHeld) fRotate += 2.0f * fElapsedTime;
		
		
		Clear(olc::DARK_CYAN);

		SetPixelMode(olc::Pixel::ALPHA);
		//DrawSprite(0, 0, sprCar, 3);
		

		matrix3x3 matFinal, matA, matB, matC, matFinalInv;
		Translate(matA, -100, -50);
		Rotate(matB, fRotate);
		MatrixMultiply(matC, matB, matA);

		Translate(matA, (float)ScreenWidth()/2, (float)ScreenHeight()/2);
		MatrixMultiply(matFinal, matA, matC);

		Invert(matFinal, matFinalInv);

		// Draws the dumb way, but leaves gaps
		/*for (int x = 0; x < sprCar->width; x++)
		{
			for (int y = 0; y < sprCar->height; y++)
			{
				olc::Pixel p = sprCar->GetPixel(x, y);

				float nx, ny;
				Forward(matFinal, (float)x, (float)y, nx, ny);
				Draw(nx, ny, p);
			}
		}*/

		// Work out bounding box of sprite post-transformation
		// by passing through sprite corner locations into 
		// transformation matrix
		float ex, ey;
		float sx, sy;
		float px, py;

		Forward(matFinal, 0.0f, 0.0f, px, py);
		sx = px; sy = py;
		ex = px; ey = py;

		Forward(matFinal, (float)sprCar->width, (float)sprCar->height, px, py);
		sx = std::min(sx, px); sy = std::min(sy, py);
		ex = std::max(ex, px); ey = std::max(ey, py);

		Forward(matFinal, 0.0f, (float)sprCar->height, px, py);
		sx = std::min(sx, px); sy = std::min(sy, py);
		ex = std::max(ex, px); ey = std::max(ey, py);

		Forward(matFinal, (float)sprCar->width, 0.0f, px, py);
		sx = std::min(sx, px); sy = std::min(sy, py);
		ex = std::max(ex, px); ey = std::max(ey, py);

		// Use transformed corner locations in screen space to establish
		// region of pixels to fill, using inverse transform to sample
		// sprite at suitable locations.
		for (int x = sx; x < ex; x++)
		{
			for (int y = sy; y < ey; y++)
			{
				float nx, ny;
				Forward(matFinalInv, (float)x, (float)y, nx, ny);
				olc::Pixel p = sprCar->GetPixel((int32_t)(nx + 0.5f), (int32_t)(ny + 0.5f));
				Draw(x, y, p);
			}
		}

		SetPixelMode(olc::Pixel::NORMAL);

		return true;
	}
};

int main()
{
	SpriteTransforms demo;
	if (demo.Construct(256, 240, 4, 4))
		demo.Start();
	return 0;
}