点不会通过 OpenGL 中的键盘输入移动

Question

我正在尝试在 OpenGL 中从上到下移动几个点（水平渲染）。代码运行没有任何错误。当我尝试处理诸如-> 开始移动、加速/减速或停止移动之类的事件时，它不起作用。下面是代码。

#include <gl/glut.h>
int pointStatus=0;
float pointX = 0.0f;
float pointY = 0.0f;
float speed, b = 0.5;
char s;
void Point(int x1, int y1)
{
glColor3f(1.0, 1.0, 1.0); 
glPointSize(5);
glPushMatrix();

glBegin(GL_POINTS);
glVertex2i(x1, y1);
glPopMatrix();

glEnd();
}

void Draw()
{
int x=0, y=6;
for (x = 0; x <= 6; x +=  1)
    {
        Point(x,y); 
    }
glFlush();
}

void movePoint(int s, int x, int b)//
{
if (pointStatus == 1)
{
    pointY -= b + speed;
}
if (pointY>14)
{
    pointY = -6;
}
glPushMatrix();
glTranslatef(pointX, pointY, 0);
Draw();
glPopMatrix();
}

void handleKeypress(unsigned char key, int x, int y) 
{
if (key == '1')
{                      
    pointStatus = 1; // start
    b = +0.05;
    speed = 0.5;

}

else if (key == '=' || key == '+')
{
    pointStatus = 1;    //speed up
    b = +.05;
    speed += .2;

}
else if (key == '-' || key == '_')      
{
    pointStatus = 1; //speed down 
    b = -.05;
    speed -= .2;
}
else if (key == '2')
{
    pointStatus = 0; //stop
    speed = 0;
}
}

void myDisplay(void)
{
movePoint(s, b, speed);
//glFlush();
glutPostRedisplay();
glutSwapBuffers();
}

void Initialize() {
glClearColor(0.435294, 0.258824, 0.258824,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-14.0, 14.0, -14.0, 14.0, -1.0, 10.0); // left, right, bottom, top, near and far
}

int main(int iArgc, char** cppArgv) {
glutInit(&iArgc, cppArgv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(700,500);
glutInitWindowPosition(400, 200);
glutCreateWindow("tuntaa");
Initialize();

glutDisplayFunc(myDisplay);
glutKeyboardFunc(handleKeypress);
glutMainLoop();
return 0;
}

Answer 1

• 不要从显示回调中调用 glutPostRedisplay()，如果您希望该行为通过 glutIdleFunc() 设置空闲回调。
• 不要从绘图函数更新状态，在单独的通道中执行。
• 您缺少glClear()。
• 重置您的投影并对每一帧进行建模，有助于防止难以诊断的错误。
• 如果您要使用glutSwapBuffers()，请使用GLUT_DOUBLE。
• 如果你想要一个均匀的帧速率（在没有可靠的垂直同步的情况下）设置一个计时器回调并调用glutPostRedisplay()（并重新启动计时器）。您也可以在那里进行物理更新。
• 奖励积分：glutGet(GLUT_ELAPSED_TIME) & Fix your timestep!

大家一起：

#include <GL/glut.h>
#include <map>

std::map< int, bool > keys;
void special( int key, int x, int y )
{
    keys[ key ] = true;
}
void specialUp( int key, int x, int y )
{
    keys[ key ] = false;
}

float xpos = 0;
float ypos = 0;
void update()
{
    const float speed = 1.0;
    if( keys[ GLUT_KEY_LEFT ] )
    {
        xpos -= speed;
    }
    if( keys[ GLUT_KEY_RIGHT ] )
    {
        xpos += speed;
    }
    if( keys[ GLUT_KEY_UP ] )
    {
        ypos += speed;
    }
    if( keys[ GLUT_KEY_DOWN ] )
    {
        ypos -= speed;
    }
}

void display()
{
    glClearColor( 0.435294, 0.258824, 0.258824, 0.0 );
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    glOrtho( -100, 100, -100, 100, -1, 1 );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    glTranslatef( xpos, ypos, 0 );
    glScalef( 10, 10, 1 );
    glBegin( GL_QUADS );
    glVertex2i( -1, -1 );
    glVertex2i(  1, -1 );
    glVertex2i(  1,  1 );
    glVertex2i( -1,  1 );
    glEnd();

    glutSwapBuffers();
}

void timer( int value )
{
    update();
    glutTimerFunc( 16, timer, 0 );
    glutPostRedisplay();
}

int main( int argc, char **argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
    glutInitWindowSize( 640, 640 );
    glutCreateWindow( "GLUT" );
    glutDisplayFunc( display );

    glutSpecialFunc( special );
    glutSpecialUpFunc( specialUp );

    glutTimerFunc( 0, timer, 0 );
    glutMainLoop();
    return 0;
}