Question

我正在尝试为刀片创建扭曲效果（不旋转）但它根本不起作用。特别是，我试图使用glRotatef函数来旋转轴并使其显示为刀片扭曲。

任何帮助都会很棒。

enter image description here

#include <GL/glut.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#define PI 3.14159265

static GLfloat lpos[] = { 0.0, 0.0, 4.0, 1.0 };
static GLfloat white[] = { 1.0, 1.0, 1.0, 1.0 };
static GLfloat black[] = { 0.0, 0.0, 0.0, 1.0 };
static GLfloat red[] = { 1.0, 0.0, 0.0, 1.0 };
static GLfloat yellow[] = { 1.0, 1.0, 0.0, 1.0 };
static float alpha = 0.0;
static float beta = PI / 6.0;
static float zoom = 10.0;
static bool lightSource = true;
float twistConstant = 0;
float rotateConstant = 0;
float numberOfObj = 3;
float numberOfTriangles = 1;
static GLdouble cpos[3];



void DrawTopTriangleSet(){
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, yellow);
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, yellow);
    glBegin(GL_TRIANGLE_STRIP);

    for (int i = 180; i >= 0; i = i - numberOfTriangles){
        if (i > 90){
            glPushMatrix();
            glLoadIdentity();
            glRotatef(i, 1, 0, 0);
            glPopMatrix();
        }
        glNormal3f(0, sin(PI / 4 + twistConstant), cos(PI / 4 + twistConstant - PI / 4));
        glVertex3f(i*PI / 180, 0, 0.5*sin(i*PI / 180));
        glVertex3f(i*PI / 180, 0.5*sin(i*PI / 180), twistConstant*-sin(i*PI / 180));
    }
    glEnd();
}

void DrawBottomTriangleSet(){
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, yellow);
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, yellow);
    glBegin(GL_TRIANGLE_STRIP);

    for (int i = 180; i >= 0; i = i - numberOfTriangles){
        if (i > 90){
            glPushMatrix();
            glLoadIdentity();
            glRotatef(i, 1, 0, 0);
            glPopMatrix();
        }
        glNormal3f(0, -sin(PI / 4 + twistConstant), cos(PI / 4 + twistConstant - PI / 4));
        glVertex3f(i*PI / 180, -0.5*sin(i*PI / 180), twistConstant*sin(i*PI / 180));
        glVertex3f(i*PI / 180, 0, 0.5*sin(i*PI / 180));
    }

    glEnd();
}

void DrawBackTriangleSet(){
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, yellow);
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, yellow);
    glBegin(GL_TRIANGLE_STRIP);


    for (int i = 180; i >= 0; i = i - numberOfTriangles){
        if (i > 90){
            glPushMatrix();
            glLoadIdentity();
            glRotatef(i, 1, 0, 0);
            glPopMatrix();
        }
        glNormal3f(0, 5 * sin(PI - twistConstant), 5 * cos(PI - twistConstant));
        glVertex3f(i*PI / 180, 0.5*sin(i*PI / 180), twistConstant*-sin(i*PI / 180));
        glVertex3f(i*PI / 180, -0.5*sin(i*PI / 180), twistConstant*sin(i*PI / 180));
    }
    glEnd();

}

void DrawInsideTriangleSet(){
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glBegin(GL_TRIANGLE_STRIP);

    for (int i = 180; i >= 0; i = i - numberOfTriangles){
        if (i > 90){
            glPushMatrix();
            glLoadIdentity();
            glRotatef(i, 1, 0, 0);
            glPopMatrix();
        }
        glVertex3f(i*PI / 180, 0.5*sin(i*PI / 180), twistConstant*-sin(i*PI / 180));
        glVertex3f(i*PI / 180, 0, 0.5*sin(i*PI / 180));
        glVertex3f(i*PI / 180, -0.5*sin(i*PI / 180), twistConstant*sin(i*PI / 180));
    }

    glEnd();
}

void writemessage()
{
    printf(" X => x++ <= Move light source in direction of +X\n");
    printf(" Y => y++ <= Move light source in direction of +Y\n");
    printf(" Z => z++ <= Move light source in direction of +Z\n");
    printf("\n");
    printf("^X => x-- <= Move light source in direction of -X\n");
    printf("^Y => y-- <= Move light source in direction of -Y\n");
    printf("^Z => z-- <= Move light source in direction of -Z\n");
    printf("\n");
    printf(" ^ => Move camera up\n");
    printf(" > => Move camera right\n");
    printf(" < => Move camera left\n");
    printf(" down arrow => Move camera down\n");
    printf("\n");
    printf(" t => More Twist\n");
    printf(" f => Less Twist\n");
    printf("\n");
    printf(" q => More Propeller\n");
    printf(" f => Less Propeller\n");
    printf("\n");
    printf(" w => More Triangles\n");
    printf(" s => Less Triangles\n");
    printf("\n");
    printf(" 0 => Toggling light source\n");
    printf("\n");
    printf(" r => Rotates Propeller\n");
    printf("\n");
    printf(" You can not move the light source when the light source is off !!!");
}

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, 20.0);
    glMatrixMode(GL_MODELVIEW);
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    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);
    }
    glRotatef(rotateConstant, 0, 0, 1);


    for (int i = 0; i < numberOfObj; i++){
        glPushMatrix();
        glRotatef(i * 360 / numberOfObj, 0, 0, 1);

        DrawTopTriangleSet();
        DrawBottomTriangleSet();
        DrawBackTriangleSet();
        DrawInsideTriangleSet();

        glPopMatrix();
    }


    // Cone
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red);
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, red);
    glPushMatrix();
    glTranslated(0, 0, -1.5);
    glutSolidCone(1, 2, 50, 50);
    glPopMatrix();

    // Back of Cone
    glMaterialfv(GL_FRONT, GL_EMISSION, black);
    glMaterialfv(GL_BACK, GL_EMISSION, black);
    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red);
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, red);
    glBegin(GL_POLYGON);
    glNormal3f(0, 0, 1);
    for (int i = 0; i <= 360; i++)
    {
        glVertex3f(cos(i*PI / 180) * 1, sin(i*PI / 180) * 1, -1.5);
    }

    glEnd();


    glutSwapBuffers();
    glFlush();
}


void keyboard(unsigned char key, int x, int y)
{
    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 != 15)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 't':
        if (twistConstant <= PI/4){
            twistConstant = twistConstant + 0.05;
            glutPostRedisplay();
        }
        break;
    case 'f':
        if (twistConstant >= 0){
            twistConstant = twistConstant - 0.05;
            glutPostRedisplay();
        }
        break;
    case 'r':
        rotateConstant = rotateConstant + 2;
        glutPostRedisplay();

        break;
    case 'q':
        if (numberOfObj <= 6){
            numberOfObj++;
            glutPostRedisplay();
        }

        break;
    case 'a':
        if (numberOfObj >= 0){
            numberOfObj--;
            glutPostRedisplay();
        }

        break;
    case 's':
        if (numberOfTriangles <90){
            numberOfTriangles++;
            glutPostRedisplay();
        }

        break;
    case 'w':
        if (numberOfTriangles > 1){
            numberOfTriangles--;
            glutPostRedisplay();
        }

        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;
    }
}

int main(int argc, char** argv)
{
    writemessage();
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(1200, 800);
    glutInitWindowPosition(0, 0);
    glutCreateWindow(argv[0]);

    glClearColor(0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_SMOOTH);

    glEnable(GL_LIGHTING);
    glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);
    glEnable(GL_LIGHT0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0.0, 5.0, 10.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0);

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyboard);
    glutSpecialFunc(specialkey);

    glutMainLoop();
    return 0;
}

Answer 1

只有一组有限的OpenGL调用在glBegin()和glEnd()之间有效。修改当前转换的命令不在其中。从glBegin() man page：

复制的完整有效来电列表

glBegin和glEnd之间只能使用GL命令的子集。命令是glVertex，glColor，glSecondaryColor，glIndex，glNormal，glFogCoord，glTexCoord，glMultiTexCoord，glVertexAttrib，glEvalCoord，glEvalPoint，glArrayElement，glMaterial和glEdgeFlag。此外，可以使用glCallList或glCallLists来执行仅包含前面命令的显示列表。如果在glBegin和glEnd之间执行任何其他GL命令，则设置错误标志并忽略该命令。

每当某些内容因OpenGL调用无法正常工作时，您应该尝试调用glGetError()来查看是否标记了任何错误。在这种情况下，您会看到无效调用的GL_INVALID_OPERATION错误。

由于无法在基元中间更改变换，因此最好在计算时将旋转效果所需的旋转应用于点。假设您希望绕x轴扭曲，并且计算出x，y和z而没有扭曲，那么您将使用以下内容：

float twistAng = someFactor * x;
float twistCos = cos(twistAng);
float twistSin = sin(twistAng);
float yTwisted = twistCos * y - twistSin * z;
float zTwisted = twistSin * y + twistCos * z;

然后使用(x, yTwisted, zTwisted)作为您的顶点。

刀片的Twsist效果（glRotatef）不起作用

1 个答案: