Lighting help

Graphics and GPU Programming Programming OpenGL

Started by deavik June 28, 2005 08:30 AM

9 comments, last by deavik 18 years, 9 months ago

570

Author

June 28, 2005 08:30 AM

Hi! I just loaded my first 3d model into my openGL scene! Now this was how it looked in my 3D program (Blender) on the left, and on the right, how it looks in my own program.

It looks like a box, doesn't it? What type of lighting and stuff do I need to do to make this look right? What I have done thus far:


float diffuseLight[] = {1.0f, 1.0f, 1.0f, 1.0f};
float ambiLight[] = {1.0f, 1.0f, 1.0f, 1.0f};
float posiLight[] = {0.0f, 0.0f, 1.0f, 0.0f};
// ...
  glEnable(GL_LIGHTING); 
  glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight);
  glLightfv(GL_LIGHT0, GL_AMBIENT, ambiLight);
  glLightfv(GL_LIGHT0, GL_POSITION, posiLight);
  glEnable(GL_LIGHT0);

Thanks for any help!

Aeluned

196

June 28, 2005 08:56 AM

you're going to need a glEnable(GL_COLOR_MATERIAL) in there somewhere.
you also want to set the material properties of the model (they may be included with the model - I don't know how Blender exports models);
glMaterialf* will handle that stuff for you.

deavik

570

Author

June 28, 2005 09:13 AM

OK, I tried:

glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
glMaterialfv(GL_FRONT, GL_AMBIENT, ambiLight);
glMateriali(GL_FRONT, GL_SHININESS, 128);

But it still looks the same, all white. Any other ideas? Oh, I do not have normals specified (not included with my export format which is videoscape). So how do I do this?

Aeluned

196

June 28, 2005 09:22 AM

yeah, that's a problem.

This should help you out: clicky

You'll need to normalize your normals. You can either manually do that when computing them or glEnable(GL_NORMALIZE).

you can also give glEnable(GL_AUTO_NORMAL) a quick try and see if that's the only thing you're missing. I've never had that reliably generate the proper normals for me but it should let you know if the missing normals are the only thing left for your setup - with improper or non-normalized normals the lighting will look incorrect, but you'll at least see there's lighting going on.

deavik

570

Author

June 28, 2005 09:35 AM

I just put in a glEnable(GL_AUTO_NORMAL) in my setup code (which is far away from the display list I'm using), and it still looks the same. Does it work that way - seems too easy to be true. Computing normals myself seems complicated, I may give it a try later. But if normals is not the problem?

EDIT: Hey hey, I discovered something else. Looking at the code I posted first, changing the color of the ambient light has effect, but changing the color of the diffuse light does nothing. Any idea what the problem is?

Aeluned

196

June 28, 2005 09:55 AM

Quote:Original post by deavik
I just put in a glEnable(GL_AUTO_NORMAL) in my setup code (which is far away from the display list I'm using), and it still looks the same. Does it work that way - seems too easy to be true. Computing normals myself seems complicated, I may give it a try later. But if normals is not the problem?

EDIT: Hey hey, I discovered something else. Looking at the code I posted first, changing the color of the ambient light has effect, but changing the color of the diffuse light does nothing. Any idea what the problem is?

yes. You're setting your material properties to the same value as the light - which is white.

changing the ambient light will in turn change your material properties.
for testing purposes the colors white & black aren't the best options.

try making the car red and lower the intensity of your light a bit.

GLfloat red[] = {1.0, 0.0, 0.0, 1.0};
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, red);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);

deavik

570

Author

June 28, 2005 11:38 AM

Hi, reducing light intensities helped by letting me see the diffuse light but it all looks hte same still, all the faces are lit up the same. I'm getting really frustrated now. Maybe I'll wake up tomorrow and find a *magical* solution. Aeluned you must be getting as fed up as me by now. I'm now uncertain as to whether I have missed anyhting else but the lighting... but that can't be, can it? The model is there in front of me, I just can't get it to light up properly. But hey, I'm not giving up yet!

Aeluned

196

June 28, 2005 12:03 PM

Post your relevant code and I'll take a looksy. Maybe something will occur to me that hasn't occured to you.

Kalidor

1,087

June 28, 2005 12:17 PM

Quote:Original post by deavik
...all the faces are lit up the same. I'm getting really frustrated now. Maybe I'll wake up tomorrow and find a *magical* solution...

The "magical" solution has already been stated, you NEED normals. GL_AUTO_NORMAL is only used with evaluators. For geometry you need to compute the normals yourself (or get them from the model file). How come you can't export the normals with Blender and read them in as you're loading the model?

deavik

570

Author

June 28, 2005 10:06 PM

Sorry, my last post was a stupid one. OK, normals! Kalidor I just wrote a parser for my 3D format (videoscape) and it doesn't have normals. And I dont want to change it in a hurry either. So I'll try to calculate normals myself, I know some math. Well my export format goes like this:

totalvertices
x1 y1 z1 // definition of all vertices
x2 y2 z2
....
numvertex v1 v2 v3 ... // deifition of polygons with numvertex vertices
numvertex v1 v2 v3 ...
......

So I have to take the vertices v1, v2, v3, say; form 2 vectors from them (say v1-v2 and v2-v3); then get the cross product, right? But the cross product can point in 2 directions, inside and outside. How do I pick the one that's right? Specs don't say anything about going anticlockwise or clockwise with the vertices of each polygon.

Lighting help

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