流暢地加快旋轉速度

Question

當我按下“ A”時，方塊正在加快其自身的旋轉速度，但是當我松開“ A”時，其旋轉速度比以前快，但是看上去比按“ A”時速度慢。

package backend;
import java.nio.ByteBuffer;

import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;

import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryUtil.*;

public class runGame {

    private long window;
    private GLFWKeyCallback keyCallback;
    private GLFWErrorCallback errorCallback;

    public static void main(String[] args) {
        new runGame().run();
    }
    private void run()  {
        try {
            init();
            loop();
            glfwDestroyWindow(window);
            keyCallback.release();
        } finally {
            glfwTerminate();
        }
    }
    private static final int width = 640;
    private static final int height = 480;
    private void init() {
        glfwSetErrorCallback(errorCallback);
        if(glfwInit() != GL11.GL_TRUE) {
            throw new IllegalStateException("Unable to initialize GLFW");
        }
        glfwDefaultWindowHints();
        glfwWindowHint(GLFW_VISIBLE, GL_FALSE);
        //glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

        window = glfwCreateWindow(width, height, "mazeRunner Game", 0, 0);
        if (window == NULL)
            throw new RuntimeException("Failed to create the GLFW window");
        glfwSetKeyCallback(window, keyCallback = new GLFWKeyCallback() {
            @Override
            public void invoke(long window, int key, int scancode, int action, int mods) {
                if( key == GLFW_KEY_ESCAPE && action == GLFW_RELEASE ) {
                    glfwSetWindowShouldClose(window, GL_TRUE);
                }
                if( key == GLFW_KEY_A && action == GLFW_PRESS ) {
                    speedUp = true;
                }
                if( key == GLFW_KEY_A && action == GLFW_RELEASE ) {
                    speedUp = false;
                }
            }
        });
        ByteBuffer glfwvidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());
        glfwSetWindowPos(window, 
                (GLFWvidmode.width(glfwvidmode)-width)/2,
                (GLFWvidmode.height(glfwvidmode)-height)/2);
        glfwMakeContextCurrent(window);
        glfwSwapInterval(1);
        glfwShowWindow(window);



        GLContext.createFromCurrent();
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        float aspect_ratio = ((float)height) / width;
        glFrustum(.5, -.5, -.5 * aspect_ratio, .5 * aspect_ratio, 1, 50);
        glMatrixMode(GL_MODELVIEW);
    }
    private final double fps = 60.0f;
    private double time;
    private void loop() {
        time = glfwGetTime();
        while(glfwWindowShouldClose(window) == GL_FALSE) {
            if(glfwGetTime()-time>=1/fps) { 
                glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
                time = glfwGetTime(); draw(); 
                glfwSwapBuffers(window);
                glfwPollEvents();
            }
        }
    }

    private void draw() {
        glLoadIdentity();
        glTranslatef(0.0f, 0.0f, -3.0f);
        if(speedUp==true) speed = speed+0.9f;
        drawSquare(1.0f, 0.0f, 0.0f);
    }

    boolean speedUp;
    private float speed = 20.0f;
    private void drawSquare(float red,float green,float blue) {
        glRotatef(speed*(float)time, 0.0f, 0.0f, 1.0f);
        glBegin(GL_QUADS);      // Draw The Cube Using quads
        {
            glColor3f(red, green, blue);
            glVertex2f(0, 0);
            glColor3f(red * .8f, green * .8f, blue * .8f);
            glVertex2f(0, 1);
            glColor3f(red * .5f, green * .5f, blue * .5f);
            glVertex2f(1, 1);
            glColor3f(red * .8f, green * .8f, blue * .8f);
            glVertex2f(1, 0);
        }
        glEnd();            // End Drawing The Cube
    }

}

Answer 1

不同速度的問題與您處理時間的方式有關。 變量“時間”將包含自計算程序開始計算旋轉角度以來的總時間。

glRotatef(speed*(float)time, 0.0f, 0.0f, 1.0f);

這意味着自程序啟動以來，速度差不僅適用於當前幀，還適用於所有先前的幀。 這就是為什么按下“ a”鍵時旋轉速度比預期的快。

驗證這一點很容易。 如果在程序啟動時直接按“ a”，則發現速度差異很小。 現在等待一分鍾左右，然后再次按“ a”。 現在，由於累計時間更長，所以速度差也更高。

要解決該問題，您可能應該更改旋轉計算，以便使用幀時間而不是總編程時間。 即將當前旋轉角度存儲在變量中，您可以根據速度和幀時間增加每幀。