Sprites aren't animating - c++

Question

I've been trying to update enemy sprites in my game by creating a vector of pointers to enemy objects and then using an update function to animate the sprites belonging to the objects. Although the enemy sprites are displayed on the screen, they won't get updated so they look as though they're frozen.
Here's how I've written my code:
#include<iostream>
#include<SFML/Graphics.hpp>
#include<math.h>
#include<vector>
#include<cstdlib>
#include "Enemy.h"
sf::RenderWindow window(sf::VideoMode(1920, 1080), "Zombie game", sf::Style::Default);
std::vector<Enemy*>enemies;
int main()
{
window.setFramerateLimit(60);
sf::Clock clock;
Enemy *enemy = new Enemy();
enemy->init("Assets/graphics/zombieSpriteSheetWalk.png", 4, 1.0f, sf::Vector2f(200.0f, 200.0f), sf::Vector2i(100, 107));
enemies.push_back(enemy);
while (window.isOpen())
{
sf::Event event;
while (window.pollEvent(event))
{
if (event.type == sf::Event::Closed || event.key.code == sf::Keyboard::Escape) window.close();
}
sf::Time dt = clock.restart();
for (int i = 0; i < enemies.size(); i++)
{
Enemy *enemy = enemies[i];
enemy->update(dt.asSeconds());
}
window.clear();
for (Enemy* enemy : enemies) window.draw(enemy->getSprite());
window.display();
}
return 0;
}
Enemy.h file:
#pragma once
#include<SFML/Graphics.hpp>
#include <iostream>
class Enemy
{
public:
Enemy();
~Enemy();
void init(std::string textureName, int frameCount, float animDuration, sf::Vector2f position, sf::Vector2i spriteSize);
void update(float dt);
sf::Sprite& getSprite();
void test();
private:
sf::Texture m_texture;
sf::Sprite m_sprite;
sf::Vector2f m_position;
int m_frameCount; //no. of frames in animation
float m_animDuration; //How long animation lasts (speed)
float m_elapsedTime; //keeps track of how long game has been running
sf::Vector2i m_spriteSize; //Size of each frame
};
Enemy.cpp file:
#include "Enemy.h"
Enemy::Enemy()
{
}
Enemy::~Enemy()
{
}
void Enemy::init(std::string textureName, int frameCount, float animDuration, sf::Vector2f position, sf::Vector2i spriteSize)
{
m_position = position;
m_frameCount = frameCount;
m_animDuration = animDuration;
m_spriteSize = spriteSize;
m_texture.loadFromFile(textureName.c_str());
m_sprite.setTexture(m_texture);
m_sprite.setTextureRect(sf::IntRect(0, 0, m_spriteSize.x, m_spriteSize.y));//sets which part of sprite sheet we want to display
m_sprite.setPosition(m_position);
m_sprite.setOrigin((m_texture.getSize().x / frameCount) - 25.0f, m_texture.getSize().y / 2);
}
void Enemy::update(float dt)
{
m_elapsedTime += dt;
int animFrame = static_cast<int>((m_elapsedTime / m_animDuration) * m_frameCount) % m_frameCount; //calculates current animation frame number. static_class converts float to int
m_sprite.setTextureRect(sf::IntRect(animFrame * m_spriteSize.x, 0, m_spriteSize.x, m_spriteSize.y)); //updates part of sprite sheet to be displayed
}
sf::Sprite& Enemy::getSprite()
{
return m_sprite;
}

Answer 1

You're always at time 0
From the SFML Clock header:
////////////////////////////////////////////////////////////
/// \brief Restart the clock
///
/// This function puts the time counter back to zero.
/// It also returns the time elapsed since the clock was started.
///
/// \return Time elapsed
///
////////////////////////////////////////////////////////////
Time restart();
Possible Fix
Use sf::Clock for dt instead of sf::Time and move it out of the event loop (you want it to accumulate as the program runs, not reset to 0 every time through.
Replace:
enemy->update(dt.asSeconds());
with
enemy->update(dt.getElapsedTime());
More Notes
I'm making some assumptions in this answer of types because your example was incomplete. One big omission you made was not including the class Enemy definition (especially the types of the member variables).
Based on the definition of Enemy::init, I would assume it would contain the following:
class Enemy
{
float m_elapsedTime;
float m_animDuration;
int m_frameCount;
...
However, those definitions result in the following compilation error in your version of Enemy::update:
enemy.cpp: In member function ‘void Enemy::update(float)’:
enemy.cpp:14:88: error: invalid operands of types ‘float’ and ‘int’ to binary ‘operator%’
int animFrame = static_cast<int>(((m_elapsedTime / m_animDuration) * m_frameCount) % m_frameCount);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
floats
You don't want to run animations that are a function of game time if game time is a float. The reason why not is that floating point numbers have different precision in different value ranges, the closer the number is to 0, the more precision you have, and the farther you are from 0, the less precision you have. This means that as game time progresses, your animations will not run at a constant rate (they will appear to be choppy, inconsistent, not smooth after enough time has elapsed).
A better approach would be to have an wrapping animation counter that adds the delta times and then wraps back to zero (or perhaps wraps back to 0 + some remainder, perhaps using a function like fmod). This will make sure your animation frame rate is consistent for the entire duration of the game.