How do I set material only for one object in OpenGL? - c++

Question

I have two 3D objects, and I need to set material only on one of them using glMaterial function. How can I accomplish this?
#include <GLUT/glut.h>
#include <cmath>
const int width = 1200, height = 600;
float xValue = 0.0;
float position = 0.0;
float angle = 0.0;
float shininess[] = { 1.0 };
float color[] = { 0.2, 0.2, 0.8 };
void init(void);
void display(void);
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(width, height);
glutInitWindowPosition(85, 75);
glutCreateWindow("3D объекты - освещение");
init();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
void init(void) {
glClearColor(0.0, 0.0, 0.0, 1.0);
glEnable(GL_LIGHTING);
float lightAmbient[] = { 0.5, 0.5, 0.5, 0.0 };
float lightDiffuse[] = { 0.5, 0.5, 0.5, 0.0 };
float lightSpecular[] = { 0.5, 0.5, 0.5, 0.0 };
float lightPosition[] = { -10.0, 5.0, 0.0, 1.0 };
glLightfv(GL_LIGHT0, GL_AMBIENT, lightAmbient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightDiffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, lightSpecular);
glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glOrtho(-10.0, 10.0, -5.0, 5.0, -5.0, 5.0);
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0.0, 0.0, width, height);
xValue += 0.01;
position = 5.0*cos(xValue);
angle = 270.0*sin(xValue);
glLineWidth(3);
glPushMatrix();
glTranslatef(position, 0.0, 0.0);
glRotatef(angle, 0, 1, 0);
glMaterialfv(GL_FRONT, GL_AMBIENT, color);
glMaterialfv(GL_FRONT, GL_DIFFUSE, color);
glMaterialfv(GL_FRONT, GL_SPECULAR, color);
glMaterialfv(GL_FRONT, GL_SHININESS, shininess);
glutWireTorus(1, 2, 35, 35);
glPopMatrix();
glPushMatrix();
glTranslatef(-position, 0.0, 0.0);
glRotatef(angle, 0, 1, 0);
glutSolidTorus(0.5, 3.5, 35, 35);
glPopMatrix();
glutSwapBuffers();
glutPostRedisplay();
}

Answer 1

OpenGL is a state engine. Each state is kept until it is changed again, even beyond frames. For instance you can enable and disable lighting before drawing an object:
glEnable(GL_LIGHTING);
// darw object 1
glDisable(GL_LIGHTING);
// draw object 2
ALike the material settings can be set for each object individually, before drawing the object:
glMaterialfv(...);
// darw object 1
glMaterialfv(...);
// draw object 2