c++ - opengl中渲染对象的移动

Question

我在使用 openGL 有序移动这些对象时遇到了问题。

我想要做的是让每行中的每个对象缓慢旋转并向屏幕右侧移动，当它从 View 中消失时，它应该重新出现在另一侧，就像在循环中一样。

idle 函数对单个对象运行良好，但不适用于对象组。

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

GLuint objectList;

GLfloat xRotated, yRotated, zRotated;
GLdouble size = 0.5;

float xpos = 0.0;
float ypos = 0.0;
float zpos = 0.0;

int x = 1;
float r, g, b;

/*
* Initialize depth buffer, projection matrix, light source, and lighting
* model.  Do not specify a material property here.
*/
void init(void)
{
    GLfloat ambient[] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat specular[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat position[] = { 0.0, 3.0, 3.0, 0.0 };

    GLfloat lmodel_ambient[] = { 0.2, 0.2, 0.2, 1.0 };
    GLfloat local_view[] = { 0.0 };

    glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
    glLightfv(GL_LIGHT0, GL_POSITION, position);
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);
    glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, local_view);

    glFrontFace(GL_CW);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_AUTO_NORMAL);
    glEnable(GL_NORMALIZE);
    glEnable(GL_DEPTH_TEST);


    objectList = glGenLists(1);
    glNewList(objectList, GL_COMPILE);
    glutSolidTeapot(0.5);
    glEndList();
}

/*
* Move object into position.  Use 3rd through 12th
* parameters to specify the material property.  Draw a teapot.
*/
void renderObject(GLfloat x, GLfloat y,
    GLfloat ambr, GLfloat ambg, GLfloat ambb,
    GLfloat difr, GLfloat difg, GLfloat difb,
    GLfloat specr, GLfloat specg, GLfloat specb, GLfloat shine)
{
    GLfloat mat[4];

    glPushMatrix();
    glTranslatef(x, y, 0.0);
    mat[0] = ambr; mat[1] = ambg; mat[2] = ambb; mat[3] = 1.0;
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat);
    mat[0] = difr; mat[1] = difg; mat[2] = difb;
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat);
    mat[0] = specr; mat[1] = specg; mat[2] = specb;
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat);
    glMaterialf(GL_FRONT, GL_SHININESS, shine * 128.0);
    glCallList(objectList);
    glPopMatrix();
}

void idle(void) {

    //xRotated += 0.01;
    yRotated += 0.01;
    //zRotated += 0.01;

    if (xpos > -1 && x == 1) {

        xpos = -15;
        ypos = 0;

    }
    else {
        x = 0;

        if (xpos <= 15) {
            xpos += 0.001;
            //ypos += 0.001;
        }
        else {
            xpos = 1;
            ypos = 1;
            x = 1;
        }
    }

    glutPostRedisplay();
}


void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // glRotatef(xRotated, 1.0, 0.0, 0.0);
    // rotation about Y axis
    glRotatef(xRotated, 1.0, 0.0, 0.0);
    // rotation about the Z axis
    glRotatef(yRotated, 0.0, 1.0, 0.0);
    // scale transformation
    glScalef(1.0, 1.0, 1.0);
    // glut spheres

    renderObject(2.0, 11.0, 0.05375, 0.05, 0.06625,
        0.18275, 0.17, 0.22525, 0.332741, 0.328634, 0.346435, 0.3);
    renderObject(2.0, 8.0, 0.25, 0.20725, 0.20725,
        1, 0.829, 0.829, 0.296648, 0.296648, 0.296648, 0.088);
    renderObject(2.0, 5.0, 0.1745, 0.01175, 0.01175,
        0.61424, 0.04136, 0.04136, 0.727811, 0.626959, 0.626959, 0.6);

    renderObject(6.0, 11.0, 0.25, 0.25, 0.25,
        0.4, 0.4, 0.4, 0.774597, 0.774597, 0.774597, 0.6);
    renderObject(6.0, 8.0, 0.19125, 0.0735, 0.0225,
        0.7038, 0.27048, 0.0828, 0.256777, 0.137622, 0.086014, 0.1);
    renderObject(6.0, 5.0, 0.24725, 0.1995, 0.0745,
        0.75164, 0.60648, 0.22648, 0.628281, 0.555802, 0.366065, 0.4);


    renderObject(10.0, 11.0, 0.0, 0.0, 0.0,
        0.1, 0.35, 0.1, 0.45, 0.55, 0.45, .25);
    renderObject(10.0, 8.0, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0,
        0.7, 0.6, 0.6, .25);
    renderObject(10.0, 5.0, 0.0, 0.0, 0.0, 0.55, 0.55, 0.55,
        0.70, 0.70, 0.70, .25);

    renderObject(14.0, 11.0, 0.0, 0.05, 0.0, 0.4, 0.5, 0.4,
        0.04, 0.7, 0.04, .078125);
    renderObject(14.0, 8.0, 0.05, 0.0, 0.0, 0.5, 0.4, 0.4,
        0.7, 0.04, 0.04, .078125);
    renderObject(14.0, 5.0, 0.05, 0.05, 0.05, 0.5, 0.5, 0.5,
        0.7, 0.7, 0.7, .078125);

    renderObject(18.0, 11.0, 0.0, 0.05, 0.0, 0.4, 0.5, 0.4,
        0.04, 0.7, 0.04, .078125);
    renderObject(18.0, 8.0, 0.05, 0.0, 0.0, 0.5, 0.4, 0.4,
        0.7, 0.04, 0.04, .078125);
    renderObject(18.0, 5.0, 0.05, 0.05, 0.05, 0.5, 0.5, 0.5,
        0.7, 0.7, 0.7, .078125);


    glutSwapBuffers();
}


void reshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    glOrtho(0.0, 16.0, 0.0, 16.0*(GLfloat)h / (GLfloat)w,
            -10.0, 10.0);

    glMatrixMode(GL_MODELVIEW);
}



/*
* Main Loop
*/
int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(750, 750);
    glutInitWindowPosition(50, 50);
    glutCreateWindow(argv[0]);
    init();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutIdleFunc(idle);

    glutMainLoop();
    return 0;
}

Answer 1

您必须更改说明的顺序。通过将平移矩阵乘以旋转矩阵来执行绕对象轴的旋转。

object-matrix = translation-matrix * rotation-matrix

请参阅 glRotate 的文档这清楚地说:

glRotate produces a rotation of angle degrees around the vector x y z. The current matrix (see glMatrixMode) is multiplied by a rotation matrix with the product replacing the current matrix.

像这样调整您的代码:

void renderObject(GLfloat x, GLfloat y,
    GLfloat ambr, GLfloat ambg, GLfloat ambb,
    GLfloat difr, GLfloat difg, GLfloat difb,
    GLfloat specr, GLfloat specg, GLfloat specb, GLfloat shine)
{
    glPushMatrix();

    glTranslatef(x, y, 0.0);            // translation-matrix
    glRotatef(yRotated, 0.0, 1.0, 0.0); // multiply by rotation-matrix
    glRotatef(xRotated, 1.0, 0.0, 0.0);

    .....
}

请注意，您的旋转非常轻微。出于调试原因，将 yRotated += 0.01; 更改为 yRotated += 1.0;(角度以度为单位指定)。