Delta Zeta不适用于gltranslatef [英] Delta zeta not applied by gltranslatef
问题描述
程序应模拟一个绕着另一个行星旋转的行星.
我使用gltranslatef来让行星绕更大的行星运动,但是问题是,当dz为-0.5时,行星应该隐藏在更大的行星上方.
但是,如果我测试该程序,我总会看到红色的星球超过蓝色的星球.
我还有另一个问题:行星自转太快,我该如何放慢速度?
The program should simulate a planet rotating around another planet.
I use gltranslatef to let the planet move around the bigger planet, but the problem is that the planet should hide when is over the bigger planet, because dz is -0.5.
But if I test the program I always see the red planet over the blue one.
Another problem I have: the planet rotates too fast, how do I slow it?
#include <OpenGL/OpenGL.h>
#include <GLUT/GLUT.h>
#include "utility.h"
GLfloat dx=0.0;
GLfloat dz=-0.5;
bool plus=true;
void init()
{
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 1);
glEnable(GLUT_DEPTH);
}
void render()
{
glClearColor(BLACK);
glClear(GL_COLOR_BUFFER_BIT);
glColor4f(BLUE);
glutWireSphere(0.25, 100, 100);
glPushMatrix();
glLoadIdentity();
glTranslatef(-0.5+dx, 0.0, -dz);
glColor4f(RED);
glutWireSphere(0.05, 100, 100);
glPopMatrix();
glFlush();
}
void idle()
{
if(plus)
{
dx+=0.05;
}
else
{
dx-=0.05;
}
if(dx>=1.0)
{
dx=0.5;
plus=false;
}
else if(dx<=-0.0)
{
dx=0.0;
plus=true;
}
glutPostRedisplay();
}
int main(int argc, const char * argv[])
{
glutInit(&argc, (char**)argv);
glutInitWindowSize(500, 500);
glutInitWindowPosition(150, 150);
glutInitWindowPosition(0, 0);
glutCreateWindow("Simple");
glutIdleFunc(idle);
init();
glutDisplayFunc(render);
glutMainLoop();
return 0;
}
我还不太了解空闲函数是如何工作的,为什么它被调用了那么多次?我不能选择调用空闲函数的时间间隔吗?
I haven't understood well how does the idle function work, why it gets called so many times? Can't I choose a time interval with which the idle function gets called?
更多信息:RED和BLUE是RGB浮点,在Utility.h头文件中定义.
加号是用来了解我是否必须降低或增加dx的布尔值.
More info: RED and BLUE are RGB floats, defined in the utility.h header file.
plus is a bool that is used to know if I have to decrease or increase dx.
推荐答案
试一下:
#include <GL/glut.h>
double GetSeconds()
{
return glutGet(GLUT_ELAPSED_TIME) / 1000.0f;
}
void render()
{
glClearColor(0,0,0,0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glColor3ub(0,0,255);
glutWireSphere(0.25, 100, 100);
glPushMatrix();
glLoadIdentity();
static double prv = GetSeconds();
double cur = GetSeconds();
double delta = cur - prv;
prv = cur;
const float DEG_PER_SEC = 60.0f;
static float angle = 0.0f;
angle += DEG_PER_SEC * delta;
while( angle > 360 ) angle -= 360;
glPushMatrix();
glRotatef( angle, 0, 1, 0 );
glTranslatef( 0.5, 0, 0);
glColor3ub(255,0,0);
glutWireSphere(0.05, 100, 100);
glPopMatrix();
glutSwapBuffers();
}
void reshape(int w, int h)
{
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 1);
}
void timer(int extra)
{
glutPostRedisplay();
glutTimerFunc(16, timer, 0);
}
int main(int argc, const char * argv[])
{
glutInit(&argc, (char**)argv);
glutInitWindowSize(500, 500);
glutInitWindowPosition(150, 150);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("Simple");
glutReshapeFunc(reshape);
glutTimerFunc(0, timer, 0);
glutDisplayFunc(render);
glEnable( GL_DEPTH_TEST );
glutMainLoop();
return 0;
}
重要部分:
-
显式
glMatrixMode()
通话
在 glutCreateWindow()
双缓冲需要glutSwapBuffers()
通过GL_DEPTH_BUFFER_BIT
glEnable( GL_DEPTH_TEST )
glRotatef()
用于行星旋转
基于计时器的动画
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