C++ Sandbox Game Low Performance Difficulty - c++

Question

I started Learning C++ yesterday And In that time i was rewriting my java "Falling Sand" Sandbox Game code in C++ using SFML (bit simplified since i don't know C++). but Performance in C++ was much worse in than java, what could be the reason for it, I Know this is very unfocused question, but my code is simple, i probably have a newbie mistakes which should be easy to correct.
#include <SFML/Graphics.hpp>
#include <iostream>
sf::Clock sclock;
const int WIDTH = 1440, HEIGHT = 960;
const char Blank = 0, Sand = 1, Water = 2;
const char* title = "Sandbox Simulation";
char map[WIDTH*HEIGHT];
sf::Vector2i mousePos;
int dist(int x1, int x2, int y1, int y2) {
return sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
}
int localBrushSize = 48;
short halfBrush = (short)floor(localBrushSize / 2);
char chosen = Sand;
void place() {
int randY = 0;
int randX = 0;
randX = randY = 1;
for (int y = mousePos.y - halfBrush; y <= mousePos.y + halfBrush; y += randY) {
for (int x = mousePos.x - halfBrush; x <= mousePos.x + halfBrush; x += randX) {
int I = x + y * WIDTH;
int distance = dist(mousePos.x, x, mousePos.y, y);
if (distance < halfBrush && I > 0) {
map[I] = chosen;
}
}
}
}
float Delta_Time() {
return sclock.restart().asSeconds();
}
int main() {
map[11111] = 2;
sf::RenderWindow window(sf::VideoMode(WIDTH, HEIGHT), title);
sf::Event evnt;
sf::RectangleShape pixel(sf::Vector2f(1.0f, 1.0f));
window.clear();
while (window.isOpen()) {
while (window.pollEvent(evnt)) {
switch (evnt.type) {
case sf::Event::Closed:
window.close();
break;
}
}
if (sf::Mouse::isButtonPressed(sf::Mouse::Left)) {
mousePos = sf::Mouse::getPosition(window);
place();
}
for (int y = 0; y < HEIGHT; y++) {
for (int x = 0; x < WIDTH; x++) {
int I = x + y * WIDTH;
switch (map[I]) {
case Sand:
pixel.setPosition(x, y);
pixel.setFillColor(sf::Color::Yellow);
window.draw(pixel);
break;
case Water:
pixel.setPosition(x, y);
pixel.setFillColor(sf::Color::Cyan);
window.draw(pixel);
break;
}
}
}
window.display();
}
return 0;
}

Answer 1

You might be able to make a cached / "framebuffer" like this
TOTALLY untested concept code. WIDTH/HEIGHT might be mixed up, endianess is not OK, etc.
sf::Image image;
sf:Image.create(WIDTH, HEIGHT, sf::Color(0, 0, 0));
sf::Sprite sprite;
std::array<sf::Uint8, WIDTH * HEIGHT * 4> pixels; // you can reuse this. The 4 is the size of RGBA
...
for(int y = 0; y < HEIGHT; y++) {
for(int x = 0; x < WIDTH; x++) {
int offset = (x + y * WIDTH) * 4;
pixels[offset] = sf::Color::Yellow.toInteger(); // in case BIG/Litte endian confusion you might have to do the below.
//pixels[offset + 0 ] = 255; // R?
//pixels[offset + 1 ] = 255; // G?
//pixels[offset + 2 ] = 255; // B?
//pixels[offset + 3 ] = 255; // A?
}
}
image.LoadFromPixels(WIDTH, HEIGHT, pixels);
sprite.SetImage(image);
window.Draw(sprite);
window.Display();