Question

下面是在OpenGL中手动创建球体的广泛传播代码。我对它进行了一些修改，现在它看起来更加完整，但仍然无法使其工作。它只产生一个白色的窗口。有什么想法我错过了吗？

#include <vector>
#include <math.h>
#include <GL/glut.h>

#define M_PI 3.14159265358979323846
#define M_PI_2 1.57079632679489661923

int const win_width = 512;
int const win_height = 512;

using namespace std;

class SolidSphere
{
protected:
    std::vector<GLfloat> vertices;
    std::vector<GLfloat> normals;
    std::vector<GLfloat> texcoords;
    std::vector<GLushort> indices;

public:
    SolidSphere(float radius, unsigned int rings, unsigned int sectors)
    {
        float const R = 1./(float)(rings-1);
        float const S = 1./(float)(sectors-1);
        int r, s;

        vertices.resize(rings * sectors * 3);
        normals.resize(rings * sectors * 3);
        texcoords.resize(rings * sectors * 2);
        std::vector<GLfloat>::iterator v = vertices.begin();
        std::vector<GLfloat>::iterator n = normals.begin();
        std::vector<GLfloat>::iterator t = texcoords.begin();
        for(r = 0; r < rings; r++) {
            for(s = 0; s < sectors; s++) {
                float const y = sin(-M_PI_2 + M_PI * r * R);
                float const x = cos(2*M_PI * s * S) * sin(M_PI * r * R);
                float const z = sin(2*M_PI * s * S) * sin(M_PI * r * R);

                *t++ = s*S;
                *t++ = r*R;

                *v++ = x * radius;
                *v++ = y * radius;
                *v++ = z * radius;

                *n++ = x;
                *n++ = y;
                *n++ = z;
            }
        }

        indices.resize(rings * sectors * 4);
        std::vector<GLushort>::iterator i = indices.begin();
        for (r = 0; r < rings-1; r++) {
            for(s = 0; s < sectors-1; s++) {
                *i++ = r * sectors + s;
                *i++ = r * sectors + (s+1);
                *i++ = (r+1) * sectors + (s+1);
                *i++ = (r+1) * sectors + s;
            }
        }
    }

    void draw(GLfloat x, GLfloat y, GLfloat z)
    {
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glTranslatef(x,y,z);

        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_NORMAL_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);

        glVertexPointer(3, GL_FLOAT, 0, &vertices[0]);
        glNormalPointer(GL_FLOAT, 0, &normals[0]);
        glTexCoordPointer(2, GL_FLOAT, 0, &texcoords[0]);
        glDrawElements(GL_QUADS, indices.size(), GL_UNSIGNED_SHORT, &indices[0]);
        glPopMatrix();
    }
};

SolidSphere sphere(1, 12, 24);

void display()
{
    float const win_aspect = (float)win_width/(float)win_height;

    glViewport(0, 0, win_width, win_height);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45, win_aspect, 1, 10);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

#ifdef DRAW_WIREFRAME
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
#endif
    sphere.draw(0, 0, -5);

    glutSwapBuffers();
}

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowSize(win_width, win_height);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("3D Sphere");
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

whitewindow

Answer 1

对glDrawElements的调用必须如下所示

    glDrawElements(GL_QUADS, indices.size(), GL_UNSIGNED_SHORT, &indices[0]);

此外，由于draw方法是内联编写的，因此SolidSphere::必须为它添加前缀（仅当该方法在类外定义时才有效。

您发布的代码源自我一年多前提供的StackOverflow答案：https://stackoverflow.com/a/5989676/524368

如果你看一下这个答案，draw的定义和glDrawElements调用是正确的，答案中代码的任何编辑都是针对其他部分的，但不是这个。因此无论你从哪里获取代码，都会因错误而改变。

OpenGL / C ++ 3D球体

1 个答案: