C 什么会导致OpenGL中的多边形渲染混乱?
我试图获得一些OpenGL的实际操作经验,所以我一直在编写一些基本程序。下面这个简短的程序是我第一次尝试渲染一个实体对象——一个旋转的立方体——但由于某种原因,一些背面的多边形似乎被正面的多边形所覆盖。我的问题是什么会导致这种情况?这和深度缓冲区有关吗?我发现,在这种情况下,启用面部剔除将隐藏效果,但为什么这是必要的呢?被较近的面遮挡的面不应该被隐藏吗C 什么会导致OpenGL中的多边形渲染混乱?,c,opengl,glut,depth-buffer,culling,C,Opengl,Glut,Depth Buffer,Culling,我试图获得一些OpenGL的实际操作经验,所以我一直在编写一些基本程序。下面这个简短的程序是我第一次尝试渲染一个实体对象——一个旋转的立方体——但由于某种原因,一些背面的多边形似乎被正面的多边形所覆盖。我的问题是什么会导致这种情况?这和深度缓冲区有关吗?我发现,在这种情况下,启用面部剔除将隐藏效果,但为什么这是必要的呢?被较近的面遮挡的面不应该被隐藏吗 #include <GL/gl.h> #include <GL/glu.h> #include <GL/glut.
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
typedef struct{
int width;
int height;
char * title;
} window;
window win;
float theta = 0;
const float rotRate = 0.05;//complete rotations per second
int lastTime;
const float verts[][3] = {
{0.0,0.0,0.0},
{1.0,0.0,0.0},
{0.0,1.0,0.0},
{0.0,0.0,1.0},
{0.0,1.0,1.0},
{1.0,0.0,1.0},
{1.0,1.0,0.0},
{1.0,1.0,1.0}};
const int faceIndices[][4] = {
{3,5,7,4},//front
{1,0,2,6},//back
{4,7,6,2},//top
{0,1,5,3},//bottom
{5,1,6,7},//right
{0,3,4,2}};//left
void display(){
//timing and rotation
int currentTime = glutGet(GLUT_ELAPSED_TIME);
int dt = lastTime - currentTime;
lastTime = currentTime;
theta += (float)dt/1000.0*rotRate*360.0;
if (theta > 360.0) theta += -360.0;
//draw
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -5.0);
glRotatef(theta, 0.0, 1.0, 0.0);
glTranslatef(-1.0,-1.0,-1.0);
glScalef(2.0, 2.0, 2.0);
int f;
for(f=0; f<6;f++){
glBegin(GL_POLYGON);
int v;
for(v=0; v<4; v++){
glColor3fv(verts[faceIndices[f][v]]);
glVertex3fv(verts[faceIndices[f][v]]);
}
glEnd();
}
glutSwapBuffers();
}
void initializeGLUT(int * argc, char ** argv){
glutInit(argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(win.width, win.height);
glutCreateWindow("OpenGL Cube");
glutDisplayFunc(display);
glutIdleFunc(display);
}
void initializeGL(){
//Setup Viewport matrix
glViewport(0,0,win.width, win.height);
//Setup Projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45,(float) win.width/win.height, 0.1, 100.0);
//Initialize Modelview matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//Other
glClearColor(0.0, 0.0, 0.0, 0.0);
glClearDepth(1.0);
}
int main(int argc, char** argv){
win.width = 640;
win.height = 480;
initializeGLUT(&argc, argv);
initializeGL();
glutMainLoop();
return 0;
}
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类型定义结构{
整数宽度;
内部高度;
字符*标题;
}窗口;
窗口赢;
浮点θ=0;
恒浮子旋转率=0.05//每秒完整旋转数
最后一次;
常量浮点顶点[][3]={
{0.0,0.0,0.0},
{1.0,0.0,0.0},
{0.0,1.0,0.0},
{0.0,0.0,1.0},
{0.0,1.0,1.0},
{1.0,0.0,1.0},
{1.0,1.0,0.0},
{1.0,1.0,1.0}};
const int faceindex[][4]={
{3,5,7,4},//前面
{1,0,2,6},//返回
{4,7,6,2},//顶部
{0,1,5,3},//底部
{5,1,6,7},//对
{0,3,4,2}};//左边
无效显示(){
//定时和旋转
int currentTime=glutGet(GLUT_运行时间);
int dt=上次时间-当前时间;
lastTime=当前时间;
θ+=(浮动)dt/1000.0*旋转率*360.0;
如果(θ>360.0)θ+=-360.0;
//画
glClear(GL_颜色_缓冲_位| GL_深度_缓冲_位);
glMatrixMode(GLU模型视图);
glLoadIdentity();
glTranslatef(0.0,0.0,-5.0);
glRotatef(θ,0.0,1.0,0.0);
glTranslatef(-1.0,-1.0,-1.0);
glScalef(2.0,2.0,2.0);
int f;
对于(f=0;f
这和深度缓冲区有关吗
是的,这是一个深度缓冲区问题,您在代码中启用了深度缓冲区,但显然您丢失了一些使用深度缓冲区的步骤
通过调用glEnable(GL_depth_test)启用深度测试
glDepthFunc(GL_LEQUAL);
默认值为GL_LESSglClearDepth
设置清除值,初始值为1.0,如果需要默认值,则此步骤不是强制性的glClear(GL\u COLOR\u BUFFER\u bit | GL\u depth\u BUFFER\u bit);
glEnable(GL_CULL_FACE);
glFrontFace(GL_CCW);
glCullFace(GL_BACK);
被较近的面遮挡的面不应该被隐藏吗
不管怎样
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
typedef struct{
int width;
int height;
char * title;
} window;
window win;
float theta = 0;
const float rotRate = 0.05;//complete rotations per second
int lastTime;
const float verts[][3] = {
{0.0,0.0,0.0},
{1.0,0.0,0.0},
{0.0,1.0,0.0},
{0.0,0.0,1.0},
{0.0,1.0,1.0},
{1.0,0.0,1.0},
{1.0,1.0,0.0},
{1.0,1.0,1.0}};
const int faceIndices[][4] = {
{3,5,7,4},//front
{1,0,2,6},//back
{4,7,6,2},//top
{0,1,5,3},//bottom
{5,1,6,7},//right
{0,3,4,2}};//left
void display(){
//timing and rotation
int currentTime = glutGet(GLUT_ELAPSED_TIME);
int dt = lastTime - currentTime;
lastTime = currentTime;
theta += (float)dt/1000.0*rotRate*360.0;
if (theta > 360.0) theta += -360.0;
//draw
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -5.0);
glRotatef(theta, 0.0, 1.0, 0.0);
glTranslatef(-1.0,-1.0,-1.0);
glScalef(2.0, 2.0, 2.0);
int f;
for(f=0; f<6;f++){
glBegin(GL_POLYGON);
int v;
for(v=0; v<4; v++){
glColor3fv(verts[faceIndices[f][v]]);
glVertex3fv(verts[faceIndices[f][v]]);
}
glEnd();
}
glutSwapBuffers();
}
void initializeGLUT(int * argc, char ** argv){
glutInit(argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(win.width, win.height);
glutCreateWindow("OpenGL Cube");
glutDisplayFunc(display);
glutIdleFunc(display);
}
void initializeGL(){
//Setup Viewport matrix
glViewport(0,0,win.width, win.height);
//Setup Projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45,(float) win.width/win.height, 0.1, 100.0);
//Initialize Modelview matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//Other
glClearColor(0.0, 0.0, 0.0, 0.0);
glClearDepth(1.0);
}
int main(int argc, char** argv){
win.width = 640;
win.height = 480;
initializeGLUT(&argc, argv);
initializeGL();
glutMainLoop();
return 0;
}
是的,这是有道理的,因为我们是人类,但对于计算机来说,你有责任告诉它如何做到这一点
参考资料:
这可以帮助您理解这个问题。因为OpenGL在moddels的正面和背面是不同的