Question

在许多OpenGL教程中，例如swiftless tutorials以及许多其他人，只要场景中有动画并且窗口调整大小，动画的速度就会改变。
奇怪行为的描述

当窗口很小时，动画加速
当窗口很大时动画减慢

是否有解释？

#include <GL/glew.h> // Include the GLEW header file  
#include <GL/glut.h> // Include the GLUT header file  

bool* keyStates = new bool[256]; // Create an array of boolean values of length 256 (0-255)  

bool movingUp = false; // Whether or not we are moving up or down  
float yLocation = 0.0f; // Keep track of our position on the y axis.  

float yRotationAngle = 0.0f; // The angle of rotation for our object  

void keyOperations (void) {  
    if (keyStates[GLUT_KEY_LEFT]) { // If the left arrow key has been pressed  
        // Perform left arrow key operations  
    }  
}  

void display (void) {  
    keyOperations();  

    glClearColor(1.0f, 0.0f, 0.0f, 1.0f); // Clear the background of our <a title="window" href="http://www.swiftless.com/tutorials/opengl/window.html">window</a> to red  
    glClear(GL_COLOR_BUFFER_BIT); //Clear the colour buffer (more buffers later on)  
    glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations  

    glTranslatef(0.0f, 0.0f, -5.0f); // Push eveything 5 units back into the scene, otherwise we won't see the primitive  

    glTranslatef(0.0f, yLocation, 0.0f); // Translate our object along the y axis  

    glRotatef(yRotationAngle, 0.0f, 1.0f, 0.0f); // Rotate our object around the y axis  

    glutWireCube(2.0f); // Render the primitive  

    glFlush(); // Flush the OpenGL buffers to the window  

    if (movingUp) // If we are moving up  
        yLocation -= 0.005f; // Move up along our yLocation  
    else  // Otherwise  
        yLocation += 0.005f; // Move down along our yLocation  

    if (yLocation < -3.0f) // If we have gone up too far  
        movingUp = false; // Reverse our direction so we are moving down  
    else if (yLocation > 3.0f) // Else if we have gone down too far  
        movingUp = true; // Reverse our direction so we are moving up  

    yRotationAngle += 0.005f; // Increment our rotation value  

    if (yRotationAngle > 360.0f) // If we have rotated beyond 360 degrees (a full rotation)  
        yRotationAngle -= 360.0f; // Subtract 360 degrees off of our rotation  
}  

void reshape (int width, int height) {  
    glViewport(0, 0, (GLsizei)width, (GLsizei)height); // Set our viewport to the size of our window  
    glMatrixMode(GL_PROJECTION); // Switch to the projection matrix so that we can manipulate how our scene is viewed  
    glLoadIdentity(); // Reset the projection matrix to the identity matrix so that we don't get any artifacts (cleaning up)  

    gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0); // Set the Field of view angle (in degrees), the aspect ratio of our window, and the new and far planes  

    glMatrixMode(GL_MODELVIEW); // Switch back to the model view matrix, so that we can start drawing shapes correctly  
}  

void keyPressed (unsigned char key, int x, int y) {  
    keyStates[key] = true; // Set the state of the current key to pressed  
}  

void keyUp (unsigned char key, int x, int y) {  
    keyStates[key] = false; // Set the state of the current key to not pressed  
}  

int main (int argc, char **argv) {  
    glutInit(&argc, argv); // Initialize GLUT  
    glutInitDisplayMode (GLUT_SINGLE); // Set up a basic display buffer (only single buffered for now)  
    glutInitWindowSize (500, 500); // Set the width and height of the window  
    glutInitWindowPosition (100, 100); // Set the position of the window  
    glutCreateWindow ("You’re first OpenGL Window"); // Set the title for the window  

    glutDisplayFunc(display); // Tell GLUT to use the method "display" for rendering  

    glutIdleFunc(display); // Tell GLUT to use the method "display" as our idle method as well  

    glutReshapeFunc(reshape); // Tell GLUT to use the method "reshape" for reshaping  

    glutKeyboardFunc(keyPressed); // Tell GLUT to use the method "keyPressed" for key presses  
    glutKeyboardUpFunc(keyUp); // Tell GLUT to use the method "keyUp" for key up events  

    glutMainLoop(); // Enter GLUT's main loop  
}

Answer 1

这是写它的方式，它使用“尽可能快”的渲染方法。这与禁用V-Sync一起使动画速度取决于计算一帧像素所需的时间。窗口越大，填充的像素就越多（查找关键字 fillrate ）。

解决方法是，测量渲染帧之间的时间并推进动画。

当窗口大小增加时，opengl动画会变慢

1 个答案: