#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<GL/glut.h>
double cameraAngle;
void grid_and_axes() {
// draw the three major AXES
glBegin(GL_LINES);
//X axis
glColor3f(0, 1, 0); //100% Green
glVertex3f(-150, 0, 0);
glVertex3f(150, 0, 0);
//Y axis
glColor3f(0, 0, 1); //100% Blue
glVertex3f(0, -150, 0); // intentionally extended to -150 to 150, no big deal
glVertex3f(0, 150, 0);
//Z axis
glColor3f(1, 1, 1); //100% White
glVertex3f(0, 0, -150);
glVertex3f(0, 0, 150);
glEnd();
//some gridlines along the field
int i;
glColor3f(0.5, 0.5, 0.5); //grey
glBegin(GL_LINES);
for (i = -10; i <= 10; i++) {
if (i == 0)
continue; //SKIP the MAIN axes
//lines parallel to Y-axis
glVertex3f(i * 10, -100, 0);
glVertex3f(i * 10, 100, 0);
//lines parallel to X-axis
glVertex3f(-100, i * 10, 0);
glVertex3f(100, i * 10, 0);
}
glEnd();
}
void display() {
//codes for Models, Camera
//clear the display
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0, 0, 0, 0); //color black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //clear buffers to preset values
/***************************
/ set-up camera (view) here
****************************/
//load the correct matrix -- MODEL-VIEW matrix
glMatrixMode(GL_MODELVIEW); //specify which matrix is the current matrix
//initialize the matrix
glLoadIdentity(); //replace the current matrix with the identity matrix [Diagonals have 1, others have 0]
//now give three info
//1. where is the camera (viewer)?
//2. where is the camera looking?
//3. Which direction is the camera's UP direction?
//gluLookAt(0,-150,20, 0,0,0, 0,0,1);
gluLookAt(150 * sin(cameraAngle), -150 * cos(cameraAngle), 50, 0, 0, 0, 0, 0, 1);
/*************************
/ Grid and axes Lines
**************************/
grid_and_axes();
/****************************
/ Add your objects from here
****************************/
/*glColor3f(1, 0, 0);
glutSolidCone(20, 20, 20, 20);
glColor3f(0, 0, 1);
GLUquadricObj *cyl = gluNewQuadric();
gluCylinder(cyl, 10, 10, 50, 20, 20);
glTranslatef(0, 0, 50);
glColor3f(1, 0, 0);
glutSolidCone(10, 20, 20, 20);
*/
glColor3f(1, 0, 0);
glutSolidCube(1);
我这里没有任何立方体 但是，如果我使用任何转换属性，如缩放或旋转，那么我得到所需的多维数据集，如
glColor3f（1,0,0）;
glScalef（50,5,60）;
glutSolidCube（1）;
问题是什么？ 如果我不使用如上所述的转换属性，我面临的另一个问题是颜色不起作用。如果我写：
glColor3f（1,0,0）;
glutSolidCone（20,20,20,20）;
对于上面的代码，颜色不起作用;我得到默认的彩色圆锥
但是，如果我将这两行更改为这三行，那么颜色就可以完美地工作：
glColor3f（1,0,0）;
glTranslatef（0,0,50）;
glutSolidCone（10,20,20,20）;
然后颜色工作;问题是什么？请帮忙
//ADD this line in the end --- if you use double buffer (i.e. GL_DOUBLE)
glutSwapBuffers();
}
void animate() {
//codes for any changes in Models, Camera
cameraAngle += 0.001; // camera will rotate at 0.002 radians per frame.
//codes for any changes in Models
//MISSING SOMETHING? -- YES: add the following
glutPostRedisplay(); //this will call the display AGAIN
}
void init() {
//codes for initialization
cameraAngle = 0; //angle in radian
//clear the screen
glClearColor(0, 0, 0, 0);
/************************
/ set-up projection here
************************/
//load the PROJECTION matrix
glMatrixMode(GL_PROJECTION);
//initialize the matrix
glLoadIdentity();
/*
gluPerspective() — set up a perspective projection matrix
fovy - Specifies the field of view angle, in degrees, in the y direction.
aspect ratio - Specifies the aspect ratio that determines the field of view in the x direction. The aspect ratio is the ratio of x (width) to y (height).
zNear - Specifies the distance from the viewer to the near clipping plane (always positive).
zFar - Specifies the distance from the viewer to the far clipping plane (always positive).
*/
gluPerspective(70, 1, 0.1, 10000.0);
}
int main(int argc, char **argv) {
glutInit(&argc, argv); //initialize the GLUT library
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
/ * glutInitDisplayMode - 显示模式 GLUT_DOUBLE - 允许在双缓冲区窗口上显示 GLUT_RGBA - 显示颜色（红色，绿色，蓝色）和alpha GLUT_DEPTH - 允许深度缓冲 * / glutInitDisplayMode（GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGB）;
glutCreateWindow("Some Title");
init(); //codes for initialization
glEnable(GL_DEPTH_TEST); //enable Depth Testing
glutDisplayFunc(display); //display callback function
glutIdleFunc(animate); //what you want to do in the idle time (when no drawing is occuring)
glutMainLoop(); //The main loop of OpenGL
return 0;
}
答案 0 :(得分：1)
我这里没有任何立方体。
你做获取一个立方体。它只是轴相交的微小斑点。当你绘制2个单位大，约160个单位，70度视野的东西时，你还期望看到什么呢？
如果我不像上面提到的那样使用转换属性，那么我面临的另一个问题就是颜色不起作用。 [...]我得到了默认的彩色圆锥。
我不知道你的意思是什么。 ＆＃34;默认颜色＆＃34;将是GL的内置颜色属性的初始值 - 即(1, 1, 1, 1) - 白色。使用您设置的代码，您将获得之前设置的颜色。所以我在这里唯一的猜测就是你没有正确考虑GL的状态机而使你感到困惑。
但除此之外，您根本不应该使用该代码 - 这是使用固定功能管道和立即模式绘图 - 现在十年以来已弃用的功能，并且 not支持完全由OpenGL的现代核心配置文件支持。试图在2017年学习这些东西是浪费时间。顺便说一句：
glutMainLoop(); //The main loop of OpenGL
不。只是没有!!! 。 OpenGL没有＆＃34;主循环＆＃34;。 GLUT不是OpenGL。老实说，这一切都很可怕。