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Graphics / Sprites stutter/shake inconsistently while moving the view

« on: March 20, 2020, 09:02:13 pm »

I have been researching this issue for a couple weeks now until I finally decided to post the question myself.

I am having an issue where when I move the view the sprites in the scene sometimes stutter or "shake". It happens every few seconds or so. Sometimes there could be perfectly smooth movement then next it's stuttering like crazy.

I have looked into Fixed Time steps, interpolation, Clamping positions to pixel perfect and other such things in the various forums posts I've seen that also have the issue. Nothing seems to work.

I am working on my laptop and have tried using both integrated graphics and nvidia GPU (GeForce GTX 1050 Ti Max-Q Design)

You can see here from the video what I mean:

and here is my current code:

#include <SFML/Graphics.hpp>

#include <time.h>
#include <iostream>

sf::Vector2f linearInterpolation(sf::Vector2f start, sf::Vector2f target, float alpha)
{
    return (target * alpha + start * (1.0f - alpha));
}

sf::Vector2f PixelPerfectClamp(sf::Vector2f position, float pixelsPerUnit)
{
        sf::Vector2f inPixels((int)std::round(position.x * pixelsPerUnit), (int)std::round(position.y * pixelsPerUnit));

        return inPixels / pixelsPerUnit;
}

static const float PPU = 16.0f;

const float MOVE_SPEED = 64.0f;

int main()
{
    const std::string windowTitle{ "Demo" };
    sf::RenderWindow window(sf::VideoMode(1920, 1080), "Shiver", sf::Style::Default);
        // Tried with V-SYNC true and Framerate limit off.
    window.setVerticalSyncEnabled(true);
        //window.setFramerateLimit(60);

    sf::View view(sf::Vector2f(0.0f, 0.0f), sf::Vector2f(320, 180));

        sf::Clock clock;
        sf::Time timeSinceLastUpdate = sf::Time::Zero;
        const sf::Time TimePerFrame = sf::seconds(1.0f / 120.0f); // Fixed Time Update rate.

    srand(time(NULL));

    sf::Texture treeTexture;
    if (!treeTexture.loadFromFile("Assets/evergreen-tree.png"))
        return 0;

    sf::Sprite player;
    player.setTexture(treeTexture);
    player.setTextureRect(sf::IntRect(0, 0, 48, 48));

    std::vector<sf::Sprite> trees;
    for (unsigned int i = 0; i < 100; ++i)
    {
        sf::Sprite tree;
        tree.setTexture(treeTexture);
        tree.setTextureRect(sf::IntRect(0, 0, 48, 48));
        tree.setPosition(rand() % 10 * i, rand() % 10 * i);
        trees.push_back(tree);
    }

        // Positions for interpolation.
    sf::Vector2f previousPos = player.getPosition();
    sf::Vector2f currentPos = player.getPosition();
       
        while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed || event.type == sf::Event::KeyPressed && event.key.code == sf::Keyboard::Escape)
                window.close();
        }

                auto frameTime = clock.restart();

                if (frameTime.asSeconds() > 0.25f)
                        frameTime = sf::seconds(0.25f);

                timeSinceLastUpdate += frameTime;

                //while (timestep.isUpdateRequired()) // this is true as long as there are unprocessed timesteps.
                while (timeSinceLastUpdate >= TimePerFrame)
        {
                        timeSinceLastUpdate -= TimePerFrame;
            previousPos = currentPos;

            sf::Vector2f velocity;
                        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Key::W))
                                velocity.y = -MOVE_SPEED;
                        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Key::A))
                                velocity.x = -MOVE_SPEED;
                        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Key::S))
                                velocity.y = MOVE_SPEED;
                        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Key::D))
                                velocity.x = MOVE_SPEED;

                        if ((velocity.y > 0.0f || velocity.y < 0.0f) && (velocity.x > 0.0f || velocity.x < 0.0f))
                                velocity *= sin(45.0f);

                        currentPos += velocity * TimePerFrame.asSeconds();
        }

                float interpolationAlpha =      timeSinceLastUpdate / TimePerFrame;

                // Tried with and without interpolating.
                sf::Vector2f newPosition = currentPos;
        //sf::Vector2f newPosition = linearInterpolation(previousPos, currentPos, interpolationAlpha);

        player.setPosition(newPosition);
        view.setCenter(newPosition);

        window.clear(sf::Color(150, 150, 150));
        window.setView(view);
        for (auto& tree : trees)
        {
            window.draw(tree);
        }
        window.draw(player);
        window.display();

    }

    return 0;
}
 

Any help would be appreciated. I have attached the sprite image as well.

Thanks!