OpenGL：图像表面上绘制的污迹
我正在尝试编写魔方的接口。
然而，当我绘制它时，立方体的表面上有污迹：
这是注释良好的代码。有人可以帮助我并运行代码并告诉我哪里可能出错吗？
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
void init() {
glClearColor(1.0f, 0.0f, 1.0f, 1.0f);
glEnable(GL_DEPTH_TEST);
}
static float x_degs = 0.0f;
static float y_degs = 0.0f;
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'q':
exit(EXIT_SUCCESS);
case 'h':
y_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'j':
x_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'k':
x_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'l':
y_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
}
}
// half the length of one card
static const float card_half_size = 1.0f;
// half the space between cards
static const float space_half_size = 0.1f;
// number of cards per face
static const int NUM_CARDS_PER_FACE = 4;
/*
// start position of center of top left card
const float start = - 3 * (card_half_size + space_half_size);
// increment between center of cards
const float incr = 2 * (card_half_size + space_half_size);
// half the size of a cube face
const float cube_half_size = 4 * (card_half_size + space_half_size);
*/
// draw a card centered at the origin
void draw_card() {
glBegin(GL_QUADS);
glVertex3f(- card_half_size, - card_half_size, 0.0f);
glVertex3f(- card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, - card_half_size, 0.0f);
glEnd();
}
// draw a cube face made up of cards
void draw_card_face() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
const float start = - 3 * (card_half_size + space_half_size);
const float incr = 2 * (card_half_size + space_half_size);
glColor3f(0.0f, 1.0f, 1.0f);
glBegin(GL_QUADS);
glVertex3f(- cube_half_size, - cube_half_size, -0.001f);
glVertex3f(- cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, - cube_half_size, -0.001f);
glEnd();
glColor3f(1.0f, 1.0f, 1.0f);
for (int i = 0; i < NUM_CARDS_PER_FACE; i++)
for (int j = 0; j < NUM_CARDS_PER_FACE; j++) {
glPushMatrix();
glTranslatef(start + i * incr, start + j * incr, 0.0f);
draw_card();
glPopMatrix();
}
}
// draw a cube made up of cards
void draw_card_cube() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
// front face
glPushMatrix();
glTranslatef(0.0f, 0.0f, cube_half_size);
draw_card_face();
glPopMatrix();
// back face
glPushMatrix();
glTranslatef(0.0f, 0.0f, - cube_half_size);
glRotatef(180.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// right face
glPushMatrix();
glTranslatef(cube_half_size, 0.0f, 0.0f);
glRotatef(90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// left face
glPushMatrix();
glTranslatef(- cube_half_size, 0.0f, 0.0f);
glRotatef(- 90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// top face
glPushMatrix();
glTranslatef(0.0f, cube_half_size, 0.0f);
glRotatef(90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
// bottom face
glPushMatrix();
glTranslatef(0.0f, - cube_half_size, 0.0f);
glRotatef(- 90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glRotatef(x_degs, 1.0f, 0.0f, 0.0f);
glRotatef(y_degs, 0.0f, 1.0f, 0.0f);
gluLookAt(-0.6f, 0.6f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
draw_card_cube();
glutSwapBuffers();
}
void reshape(int w, int h) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-15.0f, 15.0f, -15.0f, 15.0f, -15.0f, 15.0f);
glViewport(0, 0, w, h);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow(argv[0]);
init();
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
好的，我修改了代码，以便在后面绘制 0.01f 个单位的青色矩形，而不是后面 0.001f 个单位，这似乎修复了 z 冲突。但是我想使用 glPolygonOffset(factor,units) 来解决这个问题，但我无法做到这一点，因为以下 原因：
- 我不知道如何设置因子和单位（我都尝试过 1.0）。
- 我尝试过不同的值但没有结果。
这是没有出血/缝合/z-fighting 的代码：
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
void init() {
glClearColor(1.0f, 0.0f, 1.0f, 1.0f);
glEnable(GL_DEPTH_TEST);
}
static float x_degs = 0.0f;
static float y_degs = 0.0f;
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'q':
exit(EXIT_SUCCESS);
case 'h':
y_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'j':
x_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'k':
x_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'l':
y_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
}
}
// half the length of one card
static const float card_half_size = 1.0f;
// half the space between cards
static const float space_half_size = 0.1f;
// number of cards per face
static const int NUM_CARDS_PER_FACE = 4;
/*
// start position of center of top left card
const float start = - 3 * (card_half_size + space_half_size);
// increment between center of cards
const float incr = 2 * (card_half_size + space_half_size);
// half the size of a cube face
const float cube_half_size = 4 * (card_half_size + space_half_size);
*/
// draw a card centered at the origin
void draw_card() {
glBegin(GL_QUADS);
glVertex3f(- card_half_size, - card_half_size, 0.0f);
glVertex3f(- card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, - card_half_size, 0.0f);
glEnd();
}
// draw a cube face made up of cards
void draw_card_face() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
const float start = - 3 * (card_half_size + space_half_size);
const float incr = 2 * (card_half_size + space_half_size);
glColor3f(0.0f, 1.0f, 1.0f);
glBegin(GL_QUADS);
glVertex3f(- cube_half_size, - cube_half_size, -0.001f);
glVertex3f(- cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, - cube_half_size, -0.001f);
glEnd();
glColor3f(1.0f, 1.0f, 1.0f);
for (int i = 0; i < NUM_CARDS_PER_FACE; i++)
for (int j = 0; j < NUM_CARDS_PER_FACE; j++) {
glPushMatrix();
glTranslatef(start + i * incr, start + j * incr, 0.0f);
draw_card();
glPopMatrix();
}
}
// draw a cube made up of cards
void draw_card_cube() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
// front face
glPushMatrix();
glTranslatef(0.0f, 0.0f, cube_half_size);
draw_card_face();
glPopMatrix();
// back face
glPushMatrix();
glTranslatef(0.0f, 0.0f, - cube_half_size);
glRotatef(180.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// right face
glPushMatrix();
glTranslatef(cube_half_size, 0.0f, 0.0f);
glRotatef(90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// left face
glPushMatrix();
glTranslatef(- cube_half_size, 0.0f, 0.0f);
glRotatef(- 90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// top face
glPushMatrix();
glTranslatef(0.0f, cube_half_size, 0.0f);
glRotatef(90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
// bottom face
glPushMatrix();
glTranslatef(0.0f, - cube_half_size, 0.0f);
glRotatef(- 90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glRotatef(x_degs, 1.0f, 0.0f, 0.0f);
glRotatef(y_degs, 0.0f, 1.0f, 0.0f);
gluLookAt(-0.6f, 0.6f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
draw_card_cube();
glutSwapBuffers();
}
void reshape(int w, int h) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-15.0f, 15.0f, -15.0f, 15.0f, -15.0f, 15.0f);
glViewport(0, 0, w, h);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow(argv[0]);
init();
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
I am trying to code an interface to a rubik's cube.
However when I draw it there are smudges on the faces of the cube:
Here is the well-commented code. Can someone please help me and perhaps run the code and tell me where I might be going wrong?
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
void init() {
glClearColor(1.0f, 0.0f, 1.0f, 1.0f);
glEnable(GL_DEPTH_TEST);
}
static float x_degs = 0.0f;
static float y_degs = 0.0f;
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'q':
exit(EXIT_SUCCESS);
case 'h':
y_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'j':
x_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'k':
x_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'l':
y_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
}
}
// half the length of one card
static const float card_half_size = 1.0f;
// half the space between cards
static const float space_half_size = 0.1f;
// number of cards per face
static const int NUM_CARDS_PER_FACE = 4;
/*
// start position of center of top left card
const float start = - 3 * (card_half_size + space_half_size);
// increment between center of cards
const float incr = 2 * (card_half_size + space_half_size);
// half the size of a cube face
const float cube_half_size = 4 * (card_half_size + space_half_size);
*/
// draw a card centered at the origin
void draw_card() {
glBegin(GL_QUADS);
glVertex3f(- card_half_size, - card_half_size, 0.0f);
glVertex3f(- card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, - card_half_size, 0.0f);
glEnd();
}
// draw a cube face made up of cards
void draw_card_face() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
const float start = - 3 * (card_half_size + space_half_size);
const float incr = 2 * (card_half_size + space_half_size);
glColor3f(0.0f, 1.0f, 1.0f);
glBegin(GL_QUADS);
glVertex3f(- cube_half_size, - cube_half_size, -0.001f);
glVertex3f(- cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, - cube_half_size, -0.001f);
glEnd();
glColor3f(1.0f, 1.0f, 1.0f);
for (int i = 0; i < NUM_CARDS_PER_FACE; i++)
for (int j = 0; j < NUM_CARDS_PER_FACE; j++) {
glPushMatrix();
glTranslatef(start + i * incr, start + j * incr, 0.0f);
draw_card();
glPopMatrix();
}
}
// draw a cube made up of cards
void draw_card_cube() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
// front face
glPushMatrix();
glTranslatef(0.0f, 0.0f, cube_half_size);
draw_card_face();
glPopMatrix();
// back face
glPushMatrix();
glTranslatef(0.0f, 0.0f, - cube_half_size);
glRotatef(180.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// right face
glPushMatrix();
glTranslatef(cube_half_size, 0.0f, 0.0f);
glRotatef(90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// left face
glPushMatrix();
glTranslatef(- cube_half_size, 0.0f, 0.0f);
glRotatef(- 90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// top face
glPushMatrix();
glTranslatef(0.0f, cube_half_size, 0.0f);
glRotatef(90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
// bottom face
glPushMatrix();
glTranslatef(0.0f, - cube_half_size, 0.0f);
glRotatef(- 90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glRotatef(x_degs, 1.0f, 0.0f, 0.0f);
glRotatef(y_degs, 0.0f, 1.0f, 0.0f);
gluLookAt(-0.6f, 0.6f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
draw_card_cube();
glutSwapBuffers();
}
void reshape(int w, int h) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-15.0f, 15.0f, -15.0f, 15.0f, -15.0f, 15.0f);
glViewport(0, 0, w, h);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow(argv[0]);
init();
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
OK, I have revised the code so that I draw th cyan rectangles 0.01f units behind instead of 0.001f units behind and this seems to have fixed the z-fighting. However I would have liked to use glPolygonOffset(factor, units) to fix this problem but I was unable to do it, for the following
reasons:
- I don't know how to set facor and units (I've tried 1.0 for both).
- I've tried different values to no outcome.
Here is the code without the bleeding/stitching/z-fighting:
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
void init() {
glClearColor(1.0f, 0.0f, 1.0f, 1.0f);
glEnable(GL_DEPTH_TEST);
}
static float x_degs = 0.0f;
static float y_degs = 0.0f;
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'q':
exit(EXIT_SUCCESS);
case 'h':
y_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'j':
x_degs -= 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'k':
x_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
case 'l':
y_degs += 1.0f;
glutPostRedisplay();
glutSwapBuffers();
break;
}
}
// half the length of one card
static const float card_half_size = 1.0f;
// half the space between cards
static const float space_half_size = 0.1f;
// number of cards per face
static const int NUM_CARDS_PER_FACE = 4;
/*
// start position of center of top left card
const float start = - 3 * (card_half_size + space_half_size);
// increment between center of cards
const float incr = 2 * (card_half_size + space_half_size);
// half the size of a cube face
const float cube_half_size = 4 * (card_half_size + space_half_size);
*/
// draw a card centered at the origin
void draw_card() {
glBegin(GL_QUADS);
glVertex3f(- card_half_size, - card_half_size, 0.0f);
glVertex3f(- card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, card_half_size, 0.0f);
glVertex3f(card_half_size, - card_half_size, 0.0f);
glEnd();
}
// draw a cube face made up of cards
void draw_card_face() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
const float start = - 3 * (card_half_size + space_half_size);
const float incr = 2 * (card_half_size + space_half_size);
glColor3f(0.0f, 1.0f, 1.0f);
glBegin(GL_QUADS);
glVertex3f(- cube_half_size, - cube_half_size, -0.001f);
glVertex3f(- cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, cube_half_size, -0.001f);
glVertex3f(cube_half_size, - cube_half_size, -0.001f);
glEnd();
glColor3f(1.0f, 1.0f, 1.0f);
for (int i = 0; i < NUM_CARDS_PER_FACE; i++)
for (int j = 0; j < NUM_CARDS_PER_FACE; j++) {
glPushMatrix();
glTranslatef(start + i * incr, start + j * incr, 0.0f);
draw_card();
glPopMatrix();
}
}
// draw a cube made up of cards
void draw_card_cube() {
const float cube_half_size = 4 * (card_half_size + space_half_size);
// front face
glPushMatrix();
glTranslatef(0.0f, 0.0f, cube_half_size);
draw_card_face();
glPopMatrix();
// back face
glPushMatrix();
glTranslatef(0.0f, 0.0f, - cube_half_size);
glRotatef(180.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// right face
glPushMatrix();
glTranslatef(cube_half_size, 0.0f, 0.0f);
glRotatef(90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// left face
glPushMatrix();
glTranslatef(- cube_half_size, 0.0f, 0.0f);
glRotatef(- 90.0f, 0.0f, 1.0f, 0.0f);
draw_card_face();
glPopMatrix();
// top face
glPushMatrix();
glTranslatef(0.0f, cube_half_size, 0.0f);
glRotatef(90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
// bottom face
glPushMatrix();
glTranslatef(0.0f, - cube_half_size, 0.0f);
glRotatef(- 90.0f, 1.0f, 0.0f, 0.0f);
draw_card_face();
glPopMatrix();
}
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glRotatef(x_degs, 1.0f, 0.0f, 0.0f);
glRotatef(y_degs, 0.0f, 1.0f, 0.0f);
gluLookAt(-0.6f, 0.6f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
draw_card_cube();
glutSwapBuffers();
}
void reshape(int w, int h) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-15.0f, 15.0f, -15.0f, 15.0f, -15.0f, 15.0f);
glViewport(0, 0, w, h);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow(argv[0]);
init();
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}
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评论（3）
我认为你正在将棋子绘制为主立方体面的共面四边形；如果是这样的话，你遇到的问题就叫做“z战斗”。
您可以查看点 12.040 深度缓冲似乎有效，但多边形似乎会渗透到它们前面的多边形中。这是怎么回事？ 这里：
http://www.opengl.org/resources/faq/technical/depthbuffer.htm 基本上，您的深度缓冲区
没有足够的精度来解析为每个像素显示哪个四边形，从而导致了问题。
您可以手动向棋盘格四边形添加偏移量，将它们移离立方体；或者通过
glPolygonOffset使用深度偏差来解决问题。I think you're drawing your checkers as coplanar quads of the faces of your main cube ; if this is the case, the problem you encounter is called "z fighting".
You can take a look at point 12.040 Depth buffering seems to work, but polygons seem to bleed through polygons that are in front of them. What's going on? here :
http://www.opengl.org/resources/faq/technical/depthbuffer.htm
Basically, your depth buffer does not have enough precision to resolve which quad to display for each pixel, causing the problem.
You can either manually add an offset to your checker quads, to move them away from the cube ; or use depth bias through
glPolygonOffsetto solve the issue.我认为你正在尝试进行共面渲染。查看
glPolygonOffset()而不是使用像你一样的小 Z 偏移。I think you're trying to do coplanar rendering. Look into
glPolygonOffset()instead of using small Z offsets like you do.这是我从你的代码中得到的结果，用 gcc -std=c99 -lGL -lGLU -lglut ac 编译：没有污迹。你能发布你的吗？ (Ubuntu 11.10, Intel GPU)
This is what I get from your code, compiled with
gcc -std=c99 -lGL -lGLU -lglut a.c: no smudges. Can you post yours? (Ubuntu 11.10, Intel GPU)