如何更改 opengl 中圆柱体的颜色？

Question

I want to draw one cylinder using OpenGL in Visual C++. I want to make the color of the cylinder red, so I add the following code in the renderCylinder function, but it doesn't change.

glColor3f(1.0, 0.0, 0.0);

Could you help me to solve this problem?

The following codes are the full codes to make a cylinder for a test.

#include <GL/glew.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <fstream>
#include <string>
#include <cstring>
#include <cmath>
#include <iostream>

int selectedObject = 1;
bool drawThatAxis = 0;
bool lightEffect = 1;

float fovy = 60.0, aspect = 1.0, zNear = 1.0, zFar = 100.0;

float depth = 8;
float phi = 0, theta = 0;
float downX, downY;
bool leftButton = false, middleButton = false;

void renderCylinder(double x1, double y1, double z1, double x2, double y2, double z2, double radius, GLUquadricObj* quadric);
void displayCallback(void);

GLdouble width, height;
int wd;

int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH);
    glutInitWindowSize(800,600);

    wd = glutCreateWindow("3D Molecules");

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);
    glCullFace(GL_BACK);
    glEnable(GL_CULL_FACE);
    glClearColor(0.0, 0.0, 0.0, 0.0);

    GLuint id;
    id = glGenLists(1);
    
    printf("hi %d\n", id);

    GLUquadric* myQuad;
    myQuad = gluNewQuadric();

    glNewList(id, GL_COMPILE);

    renderCylinder(0, 0, 0, 5, 5, 5, 1.5, myQuad);

    glEndList();

    glutDisplayFunc(displayCallback);
    glutMainLoop();
    return 0;
}

void renderCylinder(double x1, double y1, double z1, double x2, double y2, double z2, double radius, GLUquadricObj* quadric)
{
    double vx = x2 - x1;
    double vy = y2 - y1;
    double vz = z2 - z1;
    double ax, rx, ry, rz;
    double len = sqrt(vx * vx + vy * vy + vz * vz);

    glPushMatrix();
    glColor3f(1.0, 0.0, 0.0);
    glTranslatef(x1, y1, z1);
    if (fabs(vz) < 0.0001)
    {
        glRotatef(90, 0, 1, 0);
        ax = 57.2957795 * -atan(vy / vx);
        if (vx < 0)
        {

        }
        rx = 1;
        ry = 0;
        rz = 0;
    }
    else
    {
        ax = 57.2957795 * acos(vz / len);
        if (vz < 0.0)
            ax = -ax;
        rx = -vy * vz;
        ry = vx * vz;
        rz = 0;
    }
    glRotatef(ax, rx, ry, rz);
    gluQuadricOrientation(quadric, GLU_OUTSIDE);
    gluCylinder(quadric, radius, radius, len, 10, 10);
    glPopMatrix();
}

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

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(fovy, aspect, zNear, zFar);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    gluLookAt(0, 0, 40, 0, 0, 0, 0, 1, 0);

    glTranslatef(0.0, 0.0, -depth);
    glRotatef(-theta, 1.0, 0.0, 0.0);
    glRotatef(phi, 0.0, 1.0, 0.0);

    if (lightEffect) {
        glEnable(GL_LIGHTING);
        glEnable(GL_LIGHT0);
    }
    else
    {
        glDisable(GL_LIGHTING);
        glDisable(GL_LIGHT0);
    }

    switch (selectedObject)
    {
    case (1):
        glCallList(1);
        break;
    default:
        break;
    }

    glFlush();
}

Answer 1

You have lighting ON so glColor is ignored and material & light properties are used instead...

To remedy that add this to your code near place where you enable light:

glEnable(GL_COLOR_MATERIAL);