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Javidx9 6 years ago committed by GitHub
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      OneLoneCoder_PGE_SpriteTransforms.cpp
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      car_top1.png

257
OneLoneCoder_PGE_SpriteTransforms.cpp
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/*
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, ©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;
}

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