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Baltor

Odd problem with lighting...

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I have this code (it makes an earth and a moon that rotates around it):
// found this function on the internet, not taking credit for it
int CreateSphere(XYZ c, double r, int n)
{
 int i, j;
 double theta1, theta2, theta3;
 XYZ e, p;
 if (r < 0)
  r = -r;
 if (n < 0)
  n = -n;
 if (n < 4 || r <= 0)
 {
  glBegin(GL_POINTS);
   glVertex3f(c.x,c.y,c.z);
  glEnd();
  return 0;
 }
 for (j=0;j<n/2;j++)
 {
  theta1 = j * TWOPI / n - PID2;
  theta2 = (j + 1) * TWOPI / n - PID2;
  glBegin(GL_QUAD_STRIP);
   for (i=0;i<=n;i++) 
   {
    theta3 = i * TWOPI / n;
    e.x = cos(theta2) * cos(theta3);
    e.y = sin(theta2);
    e.z = cos(theta2) * sin(theta3);
    p.x = c.x + r * e.x;
    p.y = c.y + r * e.y;
    p.z = c.z + r * e.z;
    glNormal3f(e.x,e.y,e.z);
    glTexCoord2f(i/(double)n,2*(j+1)/(double)n);
    glVertex3f(p.x,p.y,p.z);
    e.x = cos(theta1) * cos(theta3);
    e.y = sin(theta1);
    e.z = cos(theta1) * sin(theta3);
    p.x = c.x + r * e.x;
    p.y = c.y + r * e.y;
    p.z = c.z + r * e.z;
    glNormal3f(e.x,e.y,e.z);
    glTexCoord2f(i/(double)n,2*j/(double)n);
    glVertex3f(p.x,p.y,p.z);
   }
  glEnd();
 }
}

void display(void)
{
 glClear(GL_COLOR_BUFFER_BIT);
 spin = (spin + .5);
 if (spin > 360.0)
  spin = spin - 360.0;
 moonSpin = moonSpin + 1;
 if (moonSpin > 360.0)
  moonSpin = moonSpin - 360.0;
 // draw the stars
 glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, star_mat_emission); 
 glCallList(starfield);
 glutPostRedisplay();
 // draw earth
 glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, earth_mat_emission);
 glEnable(GL_TEXTURE_2D); 
 glPushMatrix();
  glPushMatrix();
   glTranslatef(400.0, 400.0, 1000.0);
   glRotatef(90, 0.0, 1.0, 0.0); 
   glRotatef(-12, 1.0, 0.0, 0.0);
   glRotatef(spin, 0.0, 1.0, 0.0); 
   TextureLoadBitmap(texEarthFileName); 
   CreateSphere(coords, 200, 50);
  glPopMatrix();
  // draw moon
  glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, moon_mat_emission);
  glPushMatrix(); 
   glTranslatef(400.0, 400.0, 1000.0);
   glRotatef(spin, 0.0, 1.0, 0.0);
   glTranslatef(300.0, 0.0, 0.0);
   glRotatef(moonSpin, 0.0, 1.0, 0.0);
   TextureLoadBitmap(texMoonFileName); 
   CreateSphere(coords, 40, 50);
  glPopMatrix();
 glPopMatrix();
 glDisable(GL_TEXTURE_2D);
 glutSwapBuffers(); 
}


but when I run it the moon rotates fine but it has a problem with the lighting where one side is lit and one side is dark that does not change. When I get rid of this line:
 glPushMatrix(); 
   glTranslatef(400.0, 400.0, 1000.0);
   //glRotatef(spin, 0.0, 1.0, 0.0);
   glTranslatef(300.0, 0.0, 0.0);
   glRotatef(moonSpin, 0.0, 1.0, 0.0);
   TextureLoadBitmap(texMoonFileName); 
   CreateSphere(coords, 40, 50);
  glPopMatrix();


it still rotates in place but not around the earth. The odd thing is the lighting problem goes away. Does anyone know what is wrong? Thanks.

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to make the moon spin on the earth do this method be before drawing the moon
glLoadIdentity -> Rotate -> Translate -> Rotate
i hope its work with you :)
bye ff8!

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Nope, it is still doing it. However, I think it might be a texture problem instead because when I set the emmission spectrum of the moon to full it is still doing it (even though it is lit up).

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Baltor,I don't see anywhere in the code calls to glLightf() that sets the light position.Anyway,the general procedure of doing things is:


void Render()
{...
glMatrixMode(GL_MODELVIEW);

glLoadIdentity();
SetCamera();//Matrix transformations that set the camera(like gluLookAt or something like that)
SetLightPos();//Set the light position


//Now just render the objects
glPushMatrix();
TransformObject();//Here,setup transformations for object,like translating,rotating,scaling...
RenderObject();
glPopMatrix();



...
}

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I put this code in at the beginning of the display() func:

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0, 0.0, 0.0, 0.0, 0.0, -100.0, 0.0, 1.0, 0.0);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);



with light_position equal to (800.0, 800.0, -1000.0, 0.0). I enabled lighting and set the properties in my init() function. I'm still getting the problem though.

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