I'm at the moment trying to Programm my first Game in SFML (and my first overall) but i ran into the Problem that i get a stutter about once a second. During such a stutter the Frametime is 3 to 4 times higher than normal which is really noticeable as long i don't run really high FPS (300+).
No Problem (at least atm) as performance is not an Issue, but:
When doing that my movement Method really freaks out and moves way way slower that it's supposed to do.
my Movement method:
void Player::Update(float frametime){
mMovementSpeedTimefactor = frametime * 60 / 1000.0f;
setMovementVector(sf::Vector2f( mMovementVector.x * mMovementSpeedTimefactor, mMovementVector.y *mMovementSpeedTimefactor));
validateMovement();
//std::cout << mTestClock->restart().asMilliseconds() << std::endl;
moveObject();
this->updateAnimation();
}
frametime is the frametime in Milliseconds, and i Multiply by 60, as my movementspeed is set as a value for pixel/second and not per frame.
movementspeed is 5, so the character should move 5 px per second, whatever FPS( and therefore Frametime) i have.
But: that gives me really jumpy movement, as those "stutterframes" result in a jump, and on nto stuttering frames the palyer moves a lot slower than it should.
my mainloop is really simple, just
while(mMainWindow->isOpen()){
HandleEvents();
Update();
Render();
}
while using the inbuild framelimiter (tried writing my own, but i get the very same result, as long as i use sf:sleep to regulate FPS for not having the cpu core running at 100% load) to 300 FPS.
So yeah, i could just set my standard speed to 1 instead of 5, but
setframeratelimit is not very accurate, so i get some variation in movementspeed, that i really not like.
anyone has an idea, what i could best do? Maybe i'm not seeing the forest for all the trees ( i actually have no idea if you say that in english :P) but as this is my first game i have no experience to look back upon.
Similar question: Movement Without Framerate Limit C++ SFML.
What you really need is fixed time step.
Take a look at the SFML Game development book source code. Here's the interesting snippet from Application.cpp:
const sf::Time Game::TimePerFrame = sf::seconds(1.f/60.f);
[...]
sf::Clock clock;
sf::Time timeSinceLastUpdate = sf::Time::Zero;
while (mWindow.isOpen())
{
sf::Time elapsedTime = clock.restart();
timeSinceLastUpdate += elapsedTime;
while (timeSinceLastUpdate > TimePerFrame)
{
timeSinceLastUpdate -= TimePerFrame;
processEvents();
update(TimePerFrame);
}
updateStatistics(elapsedTime);
render();
}
EDIT: If this is not really what you want, see "Fix your timestep!" which Laurent Gomila himself linked in the SFML forum.
When frametime is really high or really low your calculations may not work correctly because of float precision issues. I suggest setting standard speed to, maybe, 500 and mMovementSpeedTimeFactor to frametime * 60 / 10.0f and check if the issue still happens.
Related
I'm currently making a game in which I would like to limit the frames per second but I'm having problems with that. Here's what I'm doing:
I'm getting the deltaTime through this method that is executed each frame:
void Time::calc_deltaTime() {
double currentFrame = glfwGetTime();
deltaTime = currentFrame - lastFrame;
lastFrame = currentFrame;
}
deltaTime is having the value I would expect (around 0.012.... to 0.016...)
And than I'm using deltaTime to delay the frame through the Sleep windows function like this:
void Time::limitToMAXFPS() {
if(1.0 / MAXFPS > deltaTime)
Sleep((1.0 / MAXFPS - deltaTime) * 1000.0);
}
MAXFPS is equal to 60 and I'm multiplying by 1000 to convert seconds to milliseconds. Though everything seems correct I'm sill having more than 60 fps (I'm getting around 72 fps)
I also tried this method using while loop:
void Time::limitToMAXFPS() {
double diff = 1.0 / MAXFPS - deltaTime;
if(diff > 0) {
double t = glfwGetTime( );
while(glfwGetTime( ) - t < diff) { }
}
}
But still I'm getting more than 60 fps, I'm still getting around 72 fps... Am I doing something wrong or is there a better way for doing this?
How important is it that you return cycles back to the CPU? To me, it seems like a bad idea to use sleep at all. Someone please correct me if I am wrong, but I think sleep functions should be avoided.
Why not simply use an infinite loop that executes if more than a certain time interval has passed. Try:
const double maxFPS = 60.0;
const double maxPeriod = 1.0 / maxFPS;
// approx ~ 16.666 ms
bool running = true;
double lastTime = 0.0;
while( running ) {
double time = glfwGetTime();
double deltaTime = time - lastTime;
if( deltaTime >= maxPeriod ) {
lastTime = time;
// code here gets called with max FPS
}
}
Last time that I used GLFW, it seemed to self-limit to 60 fps anyway. If you are doing anything high performance orientated (game or 3D graphics), avoid anything that sleeps, unless you wanna use multithreading.
Sleep can be very inaccurate. A common phenomenon seen is that the actual time slept has a resolution of 14-15 milliseconds, which gives you a frame rate of ~70.
Is Sleep() inaccurate?
I've given up of trying to limit the fps like this... As you said Windows is very inconsistent with Sleep. My fps average is being always 64 fps and not 60. The problem is that Sleep takes as argument an integer (or long integer) so I was casting it with static_cast. But I need to pass to it as a double. 16 milliseconds each frame is different from 16.6666... That's probably the cause of this extra 4 fps (so I think).
I also tried :
std::this_thread::sleep_for(std::chrono::milliseconds(static_cast<long>(1.0 / MAXFPS - deltaTime) * 1000.0)));
and the same thing is happening with sleep_for. Then I tried passing the decimal value remaining from the milliseconds to chrono::microseconds and chrono::nanoseconds using them 3 together to get a better precision but guess what I still get the freaking 64 fps.
Another weird thing is in the expression (1.0 / MAXFPS - deltaTime) * 1000.0) sometimes (Yes, this is completely random) when I change 1000.0 to a const integer making the expression become (1.0 / MAXFPS - deltaTime) * 1000) my fps simply jumps to 74 for some reason, while the expression is completely equal to each other and nothing should happen. Both of them are double expressions I don't think is happening any type promotion here.
So I decided to force the V-sync through the function wglSwapIntervalEXT(1); in order to avoid screen tearing. And then I'm gonna use that method of multiplying deltaTime with every value that might very depending on the speed of the computer executing my game. It's gonna be a pain because I might forget to multiply some value and not noticing it on my own computer creating inconsistency, but I see no other way... Thank you all for the help though.
I've recently started using glfw for a small side project I'm working on, and I've use std::chrono along side std::this_thread::sleep_until to achieve 60fps
auto start = std::chrono::steady_clock::now();
while(!glfwWindowShouldClose(window))
{
++frames;
auto now = std::chrono::steady_clock::now();
auto diff = now - start;
auto end = now + std::chrono::milliseconds(16);
if(diff >= std::chrono::seconds(1))
{
start = now;
std::cout << "FPS: " << frames << std::endl;
frames = 0;
}
glfwPollEvents();
processTransition(countit);
render.TickTok();
render.RenderBackground();
render.RenderCovers(countit);
std::this_thread::sleep_until(end);
glfwSwapBuffers(window);
}
to add you can easily adjust FPS preference by adjusting end.
now with that said, I know glfw was limited to 60fps but I had to disable the limit with glfwSwapInterval(0); just before the while loop.
Are you sure your Sleep function accept floating point values. If it only accepts int, your sleep will be a Sleep(0) which will explain your issue.
I have a problem doing an smooth movement in c++ w/ sfml.
Someone can make an algorithm to smooth move a shape / sprite by 15 px (the sprite / shape is 15 px) by pressing a button? Thanks.
Because many other programmers might want to know that, here it is, but next time ask a more precise question
Here's my way to make a smooth movement:
Take your initial movement, lets say 25, 15 per second
Make a loop like this:
void GameEngine::GameLoop()
{
sf::Clock timer;
sf::Time tickRate;
sf::Vector2f movement(25.0,15.0); // Your movement vector
while(/* wahtever */){
tickRate = timer.restart();
yourShape.move(movement * ((float)tickRate.asMilliseconds() / 1000)); //Move your shape depending on the time elapsed between two frame
yourWindow.clear();
yourWindow.draw(yourShape);
yourWindow.display();
}
}
I am using SFML making a 2D platformer. I read so many timestep articles but they don't work well for me. I am implementing it like 2500 FPS timestep, on my desktop pc it's amazingly smooth, on my laptop it's getting 300 FPS(I check with Fraps), it's not that smooth at laptop but still playable.
Here are the code snippets:
sf::Clock clock;
const sf::Time TimePerFrame = sf::seconds(1.f/2500.f);
sf::Time TimeSinceLastUpdate = sf::Time::Zero;
sf::Time elapsedTime;
These are variables and here is the game loop,
while(!quit){
elapsedTime = clock.restart();
TimeSinceLastUpdate += elapsedTime;
while (TimeSinceLastUpdate > TimePerFrame){
TimeSinceLastUpdate -= TimePerFrame;
Player::instance()->handleAll();
}
Player::instance()->render();
}
In the Player.h, I've got movement constants,
const float GRAVITY = 0.35 /2500.0f; // Uses += every frame
const float JUMP_SPEED = -400.0f/2500.0f; //SPACE -> movementSpeed.y = JUMP_SPEED;
//When character is touching to ground
const float LAND_ACCEL = 0.075 /2500.0f; // These are using +=
const float LAND_DECEL = 1.5 /2500.0f;
const float LAND_FRICTION = 0.5 /2500.0f;
const float LAND_STARTING_SPEED = 0.075; // This uses =, instead of +=
In the handleAll function of Player class, there is
cImage.move(movementSpeed);
checkCollision();
And lastly, checkCollision function, simply checks if character's master bounding box intersects the object's rectangle from each side, sets the speed x or y to 0, then fixes the overlapping by setting character position to the edge.
//Collision
if(masterBB().intersects(objectsIntersecting[i]->GetAABB())){
//HORIZONTAL
if(leftBB().intersects(objectsIntersecting[i]->GetAABB())){
if(movementSpeed.x < 0)
movementSpeed.x = 0;
cImage.setPosition(objectsIntersecting[i]->GetAABB().left + objectsIntersecting[i]->GetAABB().width + leftBB().width , cImage.getPosition().y);
}
else if(rightBB().intersects(objectsIntersecting[i]->GetAABB())){
if(movementSpeed.x > 0)
movementSpeed.x = 0;
cImage.setPosition(objectsIntersecting[i]->GetAABB().left - rightBB().width , cImage.getPosition().y);
}
//VERTICAL
if(movementSpeed.y < 0 && topBB().intersects(objectsIntersecting[i]->GetAABB())){
movementSpeed.y = 0;
cImage.setPosition(cImage.getPosition().x , objectsIntersecting[i]->GetAABB().top + objectsIntersecting[i]->GetAABB().height + masterBB().height/2);
}
if(movementSpeed.y > 0 && bottomBB().intersects(objectsIntersecting[i]->GetAABB())){
movementSpeed.y = 0;
cImage.setPosition(cImage.getPosition().x , objectsIntersecting[i]->GetAABB().top - masterBB().height/2);
//and some state updates
}
}
I tried to use 60 FPS Timestep like million times but all speed variables become so slow, I can't simply do like *2500.0f / 60.0f to all constants, It doesn't feel same. If I get close constants, It feels "ok" but then when the collision happens, character's position is getting setted all the time and it flys out of the map because of the big lap on the object caused by high speed constants applied every frame I guess...
I need to add, Normally, the book I took the timestep code uses
cImage.move(movementSpeed*TimePerFrame.asSeconds());
but as you saw, I just put /2500.0f to every constant and I don't use it.
So, is 1/2500 seconds per frame good? If not, how can I change all of these to 1/60.0f?
You're doing it wrong.
Your monitor most likely has a refresh rate of 60 Hz (= 60 FPS), thus trying to render an image at 2500 FPS is a huge waste of resources. If the only reason for choosing 2500 FPS is that your movement doesn't work the same, haven't you ever thought about, that the problem then might be with the movement code?
At best you'd implement a fixed timestep (famous article), that way your physics can run at whatever rate you want (2500 "FPS" would still be crazy, so don't do it) and is independent from your rendering rate. So even if you get some varying FPS, it won't influence your physics.
I'm currently working on a platformer and trying to implement a timestep, but for framerate limits greater than 60 the CPU usage goes up from 1% to 25% and more.
I made this minimal program to demonstrate the issue. There are two comments (lines 10-13, lines 26-30) in the code that describe the problem and what I have tested.
Note that the FPS stuff is not relevant to the problem (I think).
I tried to keep the code short and simple:
#include <memory>
#include <sstream>
#include <iomanip>
#include <SFML\Graphics.hpp>
int main() {
// Window
std::shared_ptr<sf::RenderWindow> window;
window = std::make_shared<sf::RenderWindow>(sf::VideoMode(640, 480, 32), "Test", sf::Style::Close);
/*
When I use the setFramerateLimit() function below, the CPU usage is only 1% instead of 25%+
(And only if I set the limit to 60 or less. For example 120 increases CPU usage to 25%+ again.)
*/
//window->setFramerateLimit(60);
// FPS text
sf::Font font;
font.loadFromFile("font.ttf");
sf::Text fpsText("", font, 30);
fpsText.setColor(sf::Color(0, 0, 0));
// FPS
float fps;
sf::Clock fpsTimer;
sf::Time fpsElapsedTime;
/*
When I set framerateLimit to 60 (or anything less than 60)
instead of 120, CPU usage goes down to 1%.
When the limit is greater, in this case 120, CPU usage is 25%+
*/
unsigned int framerateLimit = 120;
sf::Time fpsStep = sf::milliseconds(1000 / framerateLimit);
sf::Time fpsSleep;
fpsTimer.restart();
while (window->isOpen()) {
// Update timer
fpsElapsedTime = fpsTimer.restart();
fps = 1000.0f / fpsElapsedTime.asMilliseconds();
// Update FPS text
std::stringstream ss;
ss << "FPS: " << std::fixed << std::setprecision(0) << fps;
fpsText.setString(ss.str());
// Get events
sf::Event evt;
while (window->pollEvent(evt)) {
switch (evt.type) {
case sf::Event::Closed:
window->close();
break;
default:
break;
}
}
// Draw
window->clear(sf::Color(255, 255, 255));
window->draw(fpsText);
window->display();
// Sleep
fpsSleep = fpsStep - fpsTimer.getElapsedTime();
if (fpsSleep.asMilliseconds() > 0) {
sf::sleep(fpsSleep);
}
}
return 0;
}
I don't want to use SFML's setFramerateLimit(), but my own implementation with the sleep because I will use the fps data to update my physics and stuff.
Is there a logic error in my code? I fail to see it, given it works with a framerate limit of for example 60 (or less). Is it because I have a 60 Hz monitor?
PS: Using SFML's window->setVerticalSync() doesn't change the results
I answered another similar question with this answer.
The thing is, it's not exactly helping you with CPU usage, but I tried your code and it is working fine under 1% cpu usage at 120 FPS (and much more). When you make a game or an interactive media with a "game-loop", you don't want to lose performance by sleeping, you want to use as much cpu time as the computer can give you. Instead of sleeping, you can process other data, like loading stuff, pathfinding algorithm, etc., or just don't put limits on rendering.
I provide some useful links and code, here it is:
Similar question: Movement Without Framerate Limit C++ SFML.
What you really need is fixed time step. Take a look at the SFML Game
development book source code. Here's the interesting snippet from
Application.cpp:
const sf::Time Game::TimePerFrame = sf::seconds(1.f/60.f);
// ...
sf::Clock clock;
sf::Time timeSinceLastUpdate = sf::Time::Zero;
while (mWindow.isOpen())
{
sf::Time elapsedTime = clock.restart();
timeSinceLastUpdate += elapsedTime;
while (timeSinceLastUpdate > TimePerFrame)
{
timeSinceLastUpdate -= TimePerFrame;
processEvents();
update(TimePerFrame);
}
updateStatistics(elapsedTime);
render();
}
If this is not really what you want, see "Fix your timestep!"
which Laurent Gomila himself linked in the SFML forum.
I suggest to use the setFrameRate limit, because it's natively implemented in SFML and will work a lot better.
For getting the elapsed time you must do :
fpsElapsedTime = fpsTimer.getElapsedTime();
If I had to implement something similar, I would do:
/* in the main loop */
fpsElapsedTime = fpsTimer.getElapsedTime();
if(fpsElapsedTime.asMillisecond() >= (1000/framerateLimit))
{
fpsTimer.restart();
// All your content
}
Other thing, use sf::Color::White or sf::Color::Black instead of (sf::Color(255,255,255))
Hope this help :)
this is driving me mad, anyway, usual story, attempting to guarantee the same speed in my very simple game across any windows machine that runs it. im doing it by specifying a 1/60 value, then ensuring a fram cant run until that value has passed in time since the last time it was called. the problem im having is 1/60 equates to 30hz for some reason, I have to set it to 1/120 to get 60hz. its also not bang on 60hz, its a little faster.
if i paste it out here, could someone tell me if they see anything wrong? or a more precise way to do it maybe?
float controlFrameRate = 1./60 ;
while (gameIsRunning)
{
frameTime += (system->getElapsedTime()-lastTime);
lastTime = system->getElapsedTime();
if(frameTime > controlFrameRate)
{
gameIsRunning = system->update();
//do stuff with the game
frameTime = .0f;
}
}
Don't call getElapsedTime twice, there may be a slight difference between the two calls. Instead, store its value, then reuse it. Also, instead of setting the frameTime to 0, subtract controlFrameRate from it, that way, if one frame takes a little longer, the next one will make up for it by being a little shorter.
while (gameIsRunning)
{
float elapsedTime = system->getElapsedTime();
frameTime += (elapsedTime-lastTime);
lastTime = elapsedTime;
if(frameTime > controlFrameRate)
{
gameIsRunning = system->update();
//do stuff with the game
frameTime -= controlFrameRate;
}
}
I'm not sure about your problem with having to set the rate to 1/120, what timing API are you using here?