我被要求制作一个简单的旋转木马,通过鼠标右键和左键旋转.对于我使用GL_LINES的棒,我遇到的问题是没有办法定义法向量或类似于我用GL_POLYGON做的事情来使照明正确.我搜索了网页,但没有找到任何解释GL_LINES照明的来源(有些人告诉我照明是自动的,我不需要为GL_LINES指定任何内容),这就是我提出问题的原因.
这是前面的屏幕截图,显示前面的一切都很好:
这是背面的屏幕截图,显示了照明方面的问题.特别是,光源位于后面,但这些光棒仍然很明亮.
这是背面的另一个屏幕截图,显示了照明方面的问题.
这是指定水平和垂直方向的两个功能:
void DrawHorizontalStick(){
glLineWidth(15);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex3f(0.0, 7.0, 0.0);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE), 0.0);
glEnd();
}
void DrawVerticalStick(){
glLineWidth(5);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE), 0.0);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE) - 1, 0.0);
glEnd();
}
这是完整的源代码:
#include <GL/glut.h>
#include <stdlib.h>
#include <Windows.h>
#include <math.h>
#include <stdio.h>
#define PI 3.14159265
#define numberOfRotationTypes 3
static GLfloat lpos[] = { 0.0, 6.0, 8.0, 1.0 };
static GLfloat black[] = { 0.0, 0.0, 0.0, 1.0 };
static GLfloat white[] = { 1.0, 1.0, 1.0, 1.0 };
static GLfloat red[] = { 1.0, 0.0, 0.0, 1.0 };
static GLfloat green[] = { 0.0, 1.0, 0.0, 1.0 };
static GLfloat blue[] = { 0.0, 0.0, 1.0, 1.0 };
static GLfloat yellow[] = { 1.0, 1.0, 0.0, 1.0 };
static GLfloat magenta[] = { 1.0, 0.0, 1.0, 1.0 };
static GLfloat cyan[] = { 0.0, 1.0, 1.0, 1.0 };
static GLfloat lightgreen[] = { 0.5, 1.0, 0.5, 1.0 };
static float alpha = 0.0;
static float beta = PI / 6.0;
static float zoom = 25.0;
static bool lightSource = true;
float numberOfTriangles = 1;
static GLdouble cpos[3];
static double fenceHeight = -0.5;
static int angle = 0;
static int angle__IN_RANGE = 0.0;
static double radian__IN_RANGE = 0.0;
static int arrayOfAnglesInRange[181];
static int id = 0;
static int speed = 0;
static int signal = 1;
static GLint window[2];
static int rotationType = 0;
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
/* since back "face" appears in wireframe mode */
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
void writemessage()
{
}
void processAngle(){
angle__IN_RANGE = arrayOfAnglesInRange[abs(angle) % 181];
}
void setRadian_IN_RANGE(){
radian__IN_RANGE = ((float)angle__IN_RANGE / 180) * PI;
}
void fillArray(){
int j = -45;
for (int i = 0; i < 181; i++)
{
if (i < 90)
arrayOfAnglesInRange[i] = j++;
else
arrayOfAnglesInRange[i] = j--;
}
//for (int i = 0; i < 182; i++)
//{
// printf("%d\n", arrayOfAnglesInRange[i]);
//}
}
void keepTrackOfID(){
int tempAngle = angle;
if (id % 4 == 0)
angle += 0;
else if (id % 4 == 1)
angle += 30;
else if (id % 4 == 2)
angle += 60;
else if (id % 4 == 3)
angle += 90;
processAngle();
setRadian_IN_RANGE();
angle = tempAngle;
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, (GLfloat)w / (GLfloat)h, 0.01, 50.0);
glMatrixMode(GL_MODELVIEW);
}
void DrawSticksArroundYard(){
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, black);
GLUquadricObj *quadObj;
// Right-Line
glPushMatrix();
glTranslatef(6.8, 1.0 + fenceHeight, -7.0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.1, 0.1, 14.0, 10, 10);
glPopMatrix();
// Left-Line
glPushMatrix();
glTranslatef(-6.8, 1.0 + fenceHeight, -7.0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.1, 0.1, 14.0, 10, 10);
glPopMatrix();
// Back-Line
glPushMatrix();
glTranslatef(-6.8, 1.0 + fenceHeight, -7.0);
glRotatef(90, 0, 1, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.1, 0.1, 13.7, 10, 10);
glRotatef(-90, 0, 1, 0);
glPopMatrix();
// Front-Line
glPushMatrix();
glTranslatef(6.8, 1.0 + fenceHeight, 7.0);
glRotatef(-90, 0, 1, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.1, 0.1, 13.7, 10, 10);
glRotatef(90, 0, 1, 0);
glPopMatrix();
// Pin-Front-Right
glPushMatrix();
glTranslatef(6.8, 0, 7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Front-Left
glPushMatrix();
glTranslatef(-6.8, 0, 7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Back-Left
glPushMatrix();
glTranslatef(-6.8, 0, -7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Back-Right
glPushMatrix();
glTranslatef(6.8, 0, -7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Back-Center
glPushMatrix();
glTranslatef(0, 0, -7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Front-Center
glPushMatrix();
glTranslatef(0, 0, 7.0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Right-Center
glPushMatrix();
glTranslatef(6.8, 0, 0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
// Pin-Left-Center
glPushMatrix();
glTranslatef(-6.8, 0, 0);
glRotatef(-90, 1, 0, 0);
quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.1, 1.3 + fenceHeight, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
}
void DrawYardFloor(){
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, lightgreen);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, lightgreen);
glBegin(GL_POLYGON);
glNormal3f(0, 1, 0);
glVertex3f(-7.3, -0.005, -7.3);
glVertex3f(-7.3, -0.005, 7.3);
glVertex3f(7.3, -0.005, 7.3);
glVertex3f(7.3, -0.005, -7.3);
glEnd();
}
void DrawCenterPin(){
glRotatef(-90, 1, 0, 0);
GLUquadricObj *quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.2, 7, 10, 10);
glRotatef(90, 1, 0, 0);
}
void DrawBase(){
glRotatef(-90, 1, 0, 0);
GLUquadricObj *quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.5, 0.1, 2, 10, 10);
glRotatef(90, 1, 0, 0);
}
void DrawTop(){
glPushMatrix();
glTranslatef(0, 7, 0);
glRotatef(-90, 1, 0, 0);
GLUquadricObj *quadObj = gluNewQuadric();
gluCylinder(quadObj, 0.2, 0.0, 0.5, 10, 10);
glRotatef(90, 1, 0, 0);
glPopMatrix();
}
void DrawHorizontalStick(){
glLineWidth(15);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex3f(0.0, 7.0, 0.0);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE), 0.0);
glEnd();
}
void DrawVerticalStick(){
glLineWidth(5);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE), 0.0);
glVertex3f(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE) - 1, 0.0);
glEnd();
}
void DrawCabin(){
// Back
glNormal3f(0.0, 0.0, -1.0);
glBegin(GL_POLYGON);
glVertex3f(0, 0, -1);
glVertex3f(0, 1, -1);
glVertex3f(2, 1, -1);
glVertex3f(2, 0, -1);
glEnd();
glNormal3f(0.0, 0.0, -1.0);
glBegin(GL_POLYGON);
glVertex3f(0, 1.7, -1);
glVertex3f(0, 2, -1);
glVertex3f(2, 2, -1);
glVertex3f(2, 1.7, -1);
glEnd();
glNormal3f(0.0, 0.0, -1.0);
glBegin(GL_POLYGON);
glVertex3f(0, 1, -1);
glVertex3f(0, 1.7, -1);
glVertex3f(0.2, 1.7, -1);
glVertex3f(0.2, 1, -1);
glEnd();
glNormal3f(0.0, 0.0, -1.0);
glBegin(GL_POLYGON);
glVertex3f(1.8, 1, -1);
glVertex3f(1.8, 1.7, -1);
glVertex3f(2, 1.7, -1);
glVertex3f(2, 1, -1);
glEnd();
// Front
glNormal3f(0.0, 0.0, 1.0);
glBegin(GL_POLYGON);
glVertex3f(2, 0, 1);
glVertex3f(2, 1, 1);
glVertex3f(0, 1, 1);
glVertex3f(0, 0, 1);
glEnd();
glNormal3f(0.0, 0.0, 1.0);
glBegin(GL_POLYGON);
glVertex3f(2, 1.7, 1);
glVertex3f(2, 2, 1);
glVertex3f(0, 2, 1);
glVertex3f(0, 1.7, 1);
glEnd();
glNormal3f(0.0, 0.0, 1.0);
glBegin(GL_POLYGON);
glVertex3f(0.2, 1, 1);
glVertex3f(0.2, 1.7, 1);
glVertex3f(0, 1.7, 1);
glVertex3f(0, 1, 1);
glEnd();
glNormal3f(0.0, 0.0, 1.0);
glBegin(GL_POLYGON);
glVertex3f(2, 1, 1);
glVertex3f(2, 1.7, 1);
glVertex3f(1.8, 1.7, 1);
glVertex3f(1.8, 1, 1);
glEnd();
// Floor
glNormal3f(0.0, -1.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 0, -1);
glVertex3f(2, 0, 1);
glVertex3f(0, 0, 1);
glVertex3f(0, 0, -1);
glEnd();
// Top
glNormal3f(0.0, 1.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 2, 1);
glVertex3f(2, 2, -1);
glVertex3f(0, 2, -1);
glVertex3f(0, 2, 1);
glEnd();
// Right
glNormal3f(1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 0, -1);
glVertex3f(2, 1, -1);
glVertex3f(2, 1, 1);
glVertex3f(2, 0, 1);
glEnd();
glNormal3f(1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 1.7, -1);
glVertex3f(2, 2, -1);
glVertex3f(2, 2, 1);
glVertex3f(2, 1.7, 1);
glEnd();
glNormal3f(1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 1, -1);
glVertex3f(2, 1.7, -1);
glVertex3f(2, 1.7, -0.8);
glVertex3f(2, 1, -0.8);
glEnd();
glNormal3f(1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(2, 1, 0.8);
glVertex3f(2, 1.7, 0.8);
glVertex3f(2, 1.7, 1);
glVertex3f(2, 1, 1);
glEnd();
// Left
glNormal3f(-1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(0, 0, -1);
glVertex3f(0, 0, 1);
glVertex3f(0, 1, 1);
glVertex3f(0, 1, -1);
glEnd();
glNormal3f(-1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(0, 1.7, -1);
glVertex3f(0, 1.7, 1);
glVertex3f(0, 2, 1);
glVertex3f(0, 2, -1);
glEnd();
glNormal3f(-1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(0, 1, -1);
glVertex3f(0, 1, -0.8);
glVertex3f(0, 1.7, -0.8);
glVertex3f(0, 1.7, -1);
glEnd();
glNormal3f(-1.0, 0.0, 0.0);
glBegin(GL_POLYGON);
glVertex3f(0, 1, 0.8);
glVertex3f(0, 1, 1);
glVertex3f(0, 1.7, 1);
glVertex3f(0, 1.7, 0.8);
glEnd();
}
void darwCabin__FINAL(){
glPushMatrix();
glTranslatef(4.0 * cos(radian__IN_RANGE), 7.0 + 4.0 * sin(radian__IN_RANGE) - 3, 0.0);
glRotatef(angle, 0, 1, 0);
glPushMatrix();
glTranslatef(-1, 0, 0);
DrawCabin();
glPopMatrix();
glRotatef(-angle, 0, 1, 0);
glPopMatrix();
}
void display(void)
{
for (int i = 0; i < 2; i++) {
glutSetWindow(window[i]); // set the current window to window[i]
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 64);
if (i == 1) {
gluLookAt(0.7, 0, 0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
glRotatef(-angle, 0, 1, 0);
glTranslatef(-4.0 * cos(radian__IN_RANGE), -5.4 + 4.0 * sin(radian__IN_RANGE), 0);
glRotatef(-angle, 0, 1, 0);
}
else if (i == 0) {
cpos[0] = zoom * cos(beta) * sin(alpha);
cpos[1] = zoom * sin(beta);
cpos[2] = zoom * cos(beta) * cos(alpha);
gluLookAt(cpos[0], cpos[1], cpos[2], 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
if (lightSource == true){
glLightfv(GL_LIGHT0, GL_POSITION, lpos);
glMaterialfv(GL_FRONT, GL_EMISSION, white);
glPushMatrix();
glTranslatef(lpos[0], lpos[1], lpos[2]);
glutSolidSphere(0.1, 10, 8);
glPopMatrix();
glMaterialfv(GL_FRONT, GL_EMISSION, black);
}
DrawYardFloor();
DrawSticksArroundYard();
DrawCenterPin();
DrawBase();
DrawTop();
glRotatef(angle, 0, 1, 0);
for (int j = 0; j < 4; j++){
glMaterialfv(GL_FRONT, GL_SPECULAR, white);
glMaterialf(GL_FRONT, GL_SHININESS, 64);
if (id % 4 == 0)
{
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, green);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, black);
}
else if (id % 4 == 1)
{
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, blue);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, black);
}
else if (id % 4 == 2)
{
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, white);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, black);
}
else if (id % 4 == 3)
{
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, cyan);
glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, black);
}
glPushMatrix();
glRotatef(j * 360 / 4, 0, 1, 0);
keepTrackOfID();
DrawHorizontalStick();
DrawVerticalStick();
darwCabin__FINAL();
id++;
glPopMatrix();
}
glRotatef(-angle, 0, 1, 0);
glFlush();
glutSwapBuffers();
}
}
void keyboard(unsigned char key, int x, int y)
{
static int polygonmode[2];
switch (key) {
case 27:
exit(0);
break;
case 'x':
if (lightSource == true)
lpos[0] = lpos[0] + 0.2;
glutPostRedisplay();
break;
case 'X':
if (lightSource == true)
lpos[0] = lpos[0] - 0.2;
glutPostRedisplay();
break;
case 'y':
if (lightSource == true)
lpos[1] = lpos[1] + 0.2;
glutPostRedisplay();
break;
case 'Y':
if (lightSource == true)
lpos[1] = lpos[1] - 0.2;
glutPostRedisplay();
break;
case 'z':
if (lightSource == true)
lpos[2] = lpos[2] + 0.2;
glutPostRedisplay();
break;
case 'Z':
if (lightSource == true)
lpos[2] = lpos[2] - 0.2;
glutPostRedisplay();
break;
case '+':
if (zoom != 1.5)zoom = zoom - 0.5;
glutPostRedisplay();
break;
case '-':
if (zoom != 30)zoom = zoom + 0.5;
glutPostRedisplay();
break;
case '0':
if (lightSource == true){
glDisable(GL_LIGHT0);
lightSource = false;
}
else{
glEnable(GL_LIGHT0);
lightSource = true;
}
glutPostRedisplay();
break;
case 'e':
if (fenceHeight < 2)
fenceHeight += 0.5;
glutPostRedisplay();
break;
case 'd':
if (fenceHeight > -0.5)
fenceHeight -= 0.5;
glutPostRedisplay();
break;
case 'w':
glGetIntegerv(GL_POLYGON_MODE, polygonmode);
if (polygonmode[0] == GL_FILL)
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
else glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glutPostRedisplay();
break;
case 'n':
angle++;
processAngle();
setRadian_IN_RANGE();
glutPostRedisplay();
break;
case 'm':
angle--;
processAngle();
setRadian_IN_RANGE();
glutPostRedisplay();
break;
default:
break;
}
}
void mouse(int button, int state, int x, int y)
{
switch (button) {
case GLUT_LEFT_BUTTON:
signal = 0;
if (speed <= 15)
speed++;
break;
case GLUT_MIDDLE_BUTTON:
case GLUT_RIGHT_BUTTON:
signal = 1;
if (speed >= 1)
speed--;
break;
default:
break;
}
}
void specialkey(GLint key, int x, int y)
{
switch (key) {
case GLUT_KEY_RIGHT:
alpha = alpha + PI / 180;
if (alpha > 2 * PI) alpha = alpha - 2 * PI;
glutPostRedisplay();
break;
case GLUT_KEY_LEFT:
alpha = alpha - PI / 180;
if (alpha < 0) alpha = alpha + 2 * PI;
glutPostRedisplay();
break;
case GLUT_KEY_UP:
if (beta < 0.45*PI) beta = beta + PI / 180;
glutPostRedisplay();
break;
case GLUT_KEY_DOWN:
if (beta > -0.05*PI) beta = beta - PI / 180;
glutPostRedisplay();
break;
default:
break;
}
}
void anim(){
if (signal == 0){
angle++;
glutPostRedisplay();
Sleep((int)(50 / speed));
}
else if (signal == 1){
if (speed != 0){
angle++;
glutPostRedisplay();
Sleep((int)(50 / speed));
}
}
}
int main(int argc, char** argv)
{
writemessage();
fillArray();
processAngle();
setRadian_IN_RANGE();
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(500, 500);
glutInitWindowPosition(0, 0);
window[0] = glutCreateWindow("First");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutIdleFunc(anim);
glutMouseFunc(mouse);
glutKeyboardFunc(keyboard);
glutSpecialFunc(specialkey);
glutInitWindowSize(500, 500);
glutInitWindowPosition(600, 10);
window[1] = glutCreateWindow("Second");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutIdleFunc(anim);
glutMouseFunc(mouse);
glutKeyboardFunc(keyboard);
glutSpecialFunc(specialkey);
glutMainLoop();
return 0;
}
最佳答案 线条照明与其他物体的照明效果相同.颜色/亮度基于法线,光照和材料参数计算.
如果您正在使用立即模式绘制命令,则可以在glVertex3f()调用行之前使用glNormal3f()指定法线.如果你没有以这种方式指定正常,那么基于先前对glNormal *()的调用的当前法线将被用作你的线的法线.
现在,明显的后续问题是:一条线的正常情况是什么?
简单的答案是:无论你想要什么,给你想要的结果.
对于典型示例,如果以线框模式绘制分析曲面,则此分析曲面的法线可用作法线.这将给出线框模型,其中阴影/亮度对应于表面的形状.
在您的示例中,最明显且可以说是最佳的方法是不绘制线条,而是使用某种薄梁/圆柱体来表示具有多边形的几何体.但作为练习,我们可以弄清楚这对于线条是如何工作的.
在这种情况下,您希望线条代表无限薄的圆柱体.实际圆柱体的法线向外指向每个顶点.但由于该线只有两个顶点,因此您必须在从终点向外指向的无限矢量集中选择一个方向,并且与该线正交.
我相信你会通过选择最接近指向视点的法向量来获得合理的结果.如果您实际使用了气缸,这将导致从气缸中心线看到的亮度.这些法线可以通过以下方式计算:
>将模型转换应用于线v1和v2的原始端点.我们称之为变换后的终点v1t和v2t.
>计算变换线的方向向量:
v1d = v2t - v1t
v1d.normalize()
>计算从线端点到视点vp的矢量,并将其相对于线的方向正交化,并将其标准化:
v1n = vp - v1
v1n -= dot(v1d * v1n) * v1d
v1n.normalize()
>将逆模型变换应用于v1n以获取原始对象空间中的法线.
>对第二个顶点执行等效计算.
通过对视点执行逆变换,然后直接在对象空间中计算法线,可以获得相同的结果.