Hi All,
I have a question about lighting in OpenGL.
I am using GLUT to draw two spheres. One has been translated to (-1.5, 0, 0). The other has been translated to (1.5, 0, 0).
I place my light at (1,1,0). You would expect both objects to be lit from different sides but what I am seeing is that the shadows, and highlights appear to be what you would see if the objects were at (0,0,0).
Is this a problem with Normals or am I missing something else here.
Any help is appreciated.
I have also included a short source example if anyone is interested.
Source:
#include <windows.h>
#include <gl\gl.h>
#include <gl\glu.h>
#include <gl\glut.h>
void init(void)
{
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_shininess[] = { 90.0 };
GLfloat light_position[] = { 1.0, 1.0, 0.0, 0.0 };
GLfloat mat_ambient[] = { 0.6, 0.6, 0.6, 1.0 };
glClearColor (0.3, 0.3, 0.3, 0.0);
glShadeModel (GL_SMOOTH);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
}
void display(void)
{
GLfloat mat_diffuse1[] = { 1.0, 0.0, 0.0, 1.0 };
GLfloat mat_diffuse2[] = { 1.0, 1.0, 0.0, 1.0 };
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse1);
glTranslatef(-1.5,0.0,0.0);
glutSolidSphere (0.5, 36, 36);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse2);
glTranslatef(3.0, 0.0, 0.0);
glutSolidSphere (0.5, 36, 36);
glFlush();
}
void reshape (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho (-1.5, 1.5, -1.5*(GLfloat)h/(GLfloat)w, 1.5*(GLfloat)h/(GLfloat)w, -40.0, 40.0);
else
glOrtho (-1.5*(GLfloat)w/(GLfloat)h, 1.5*(GLfloat)w/(GLfloat)h, -1.5, 1.5, -40.0, 40.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize (900, 500);
glutInitWindowPosition (100, 100);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMainLoop();
return 0;
}