OpenGL Lights, Old Way

• First: Set up depth testing
  • In main:
  • glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
  • In display
  • glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  • glutSwapBuffers();
  • But this does a glFlush, so that can go away.
  • in setup
  • glEnable(GL_DEPTH_TEST);
• For objects, we need to
  • Enable polygons, light lines are not too much to see
  • In setup in my case
  • glPolygonMode(GL_FRONT_AND_BACK, GL_POLYGON);
  • You might want to
  • glPolygonMode(GL_AND_BACK, GL_LINE);
  • glPolygonMode(GL_FRONT, GL_POLYGON);
  • That way you can see if any of your polygons are declared the wrong way.
  • If they are, you might want
  • void glFrontFace(GLenum mode)
    • Mode is either GL_CW, or GL_CCW
    • Default is GL_CCW
  • If you want, you can get rid of some polygons with
    • void glCullFace(GLenum mode)
    • Mode: GL_FRONT, GL_BACK, GL_FRONT_AND_BACK
    • GL_BACK is the default
    • Must be enabled with glEnable(GL_CULL_FACE)
  • Make them out of some form of material
    • void glMaterialfv(GLenum face, GLenum pname, const GLfloat * params);
      • Face: GL_FRONT, GL_BACK, GL_FRONT_AND_BACK
      • pname: GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR,GL_AMBIENT_AND_DIFFUSE
      • There are others as well, but this will do.
      • params: is a four vector
    • Shininess is a single parameter (glMaterialf)
      • face as above
      • pname: GL_SHININESS
      • param: 0 to 128
    • So in place of glColor3f I have

      GLfloat Red[]   = {1.0, 0.0, 0.0, 1.0};
      glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, White);
      glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, White);
      glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, White);
      glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 20);
      glSolidTeapot(4)
      	 

• Finally, we need to turn on the lights
  • Enable lighting:
    • The lighting model
      • In setup
      • glEnable(GL_LIGHTING);
    • And enable any lights you want to use
      • Wher the light switch is:
      • glEnable(GL_LIGHTi);
      • 0 ≤ i < GL_MAX_LIGHTS
  • Configure lights:
    • void glLightf(GLenum light, GLenum pname, GLfloat param);
    • light: GL_LIGHTi as above
    • pname:
      • GL_AMBIENT, (0,0,0,1)
      • GL_DIFFUSE, (1,1,1,1) for light 0, 0 for all others
      • GL_SPECULAR, (1,1,1,1) for light 0, 0 for all others
      • GL_POSITION,
        • Transformed like a point to eye coordinates
        • if the fourth component is 0, it is a directional light
      • GL_SPOT_DIRECTION, i
        • K point at direction for the light.
        • (0,0,-1) is the default
        • This is transformed
      • GL_SPOT_CUTOFF,
        • 0 to 90 cutoff angle
        • 0r 180 which means it is not a spotlight
        • 180 is the default
      • GL_SPOT_EXPONENT,
        • Between 0 and 128
        • 0 is default: uniform
      • GL_CONSTANT_ATTENUATION,
      • GL_LINEAR_ATTENUATION,
      • GL_QUADRATIC_ATTENUATION
        • a,b,c parameters from last time.
    • So I have
    • called from setup

      void Lights() {
          GLfloat lightDiffuse[] = {1.0, 1,0, 1.0, 1.0};
          GLfloat lightSpecular[] = {1.0, 1,0, 1.0, 1.0};
          GLfloat lightAmbient[] = {0.2, 0,2, 0.2, 1.0};
      
          glEnable(GL_LIGHTING);
          glEnable(GL_LIGHT0);
      
          glLightfv(GL_LIGHT0, GL_AMBIENT, lightAmbient);
          glLightfv(GL_LIGHT0, GL_SPECULAR, lightSpecular);
          glLightfv(GL_LIGHT0, GL_DIFFUSE, lightDiffuse);
      
          return;
      }
      	     

    • and in display:

         GLfloat lightPosition[]  = {0,4,0,1.0};
         glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
      
                   

• glNormal()