I thought it was one normal for every face..?
In immediate mode you do something like:
glNormal3f(0.0, 0.0, 1.0)
glVertex3f(-1.0, -1.0, 1.0) # Bottom Left Of The Texture
and Quad
glVertex3f( 1.0, -1.0, 1.0) # Bottom Right Of The Texture
and Quad
glVertex3f( 1.0, 1.0, 1.0) # Top Right Of The Texture and
Quad
glVertex3f(-1.0, 1.0, 1.0) # Top Left Of The Texture and
Quad
# Back Face
glNormal3f(0.0, 0.0, -1.0)
glVertex3f(-1.0, -1.0, -1.0) # Bottom Right Of The Texture
and Quad
glVertex3f(-1.0, 1.0, -1.0) # Top Right Of The Texture and
Quad
glVertex3f( 1.0, 1.0, -1.0) # Top Left Of The Texture and
Quad
glVertex3f( 1.0, -1.0, -1.0) # Bottom Left Of The Texture
and Quad
which is one per face... Is it different using vertex arrays?
Thanks,
Brandon
On Feb 27, 8:42 pm, Alex Holkner <[email protected]> wrote:
> On Sat, Feb 28, 2009 at 11:52 AM, bforrester
>
>
>
> <[email protected]> wrote:
>
> > I can't seem to get lighting to work right with glDrawElements. I have
> > been working on this for quite some time now and can't seem to figure
> > out what I'm doing wrong. After googling, testing, logging, and
> > beating my head against the keyboard, I'm hoping someone on this board
> > can point out my folly :)
>
> > I'm loading a very simple .obj file I exported from blender. When I
> > draw the object in immediate mode it lights/renders perfectly fine.
> > Immediate mode is using the same root data (vertices, face indices,
> > and calculated normals) as glDrawElements minus the pointers, so I
> > know my normal calculations are correct. When I use glDrawElements
> > the geometry is right, but the lighting is very wrong (maybe almost
> > random). It makes me think that the normals pointer isn't right, but
> > after double checking the code against examples, I'm pretty sure it's
> > right.
>
> > Anyway here are the relevant portions of my code. My gl Init
> > settings, and portions of the mesh class. Maybe a fresh (more
> > experienced) set of eyes will see something I'm glazing over.
> > for i in range(0, len(self.quads), 4):
> > p1 =Vector3( self.vertices[ (self.quads[i] * 3 ) ],
> > self.vertices[ (self.quads[i] * 3 )+1 ],
> > self.vertices[ (self.quads[i] * 3 )+2 ] )
>
> > p2 =Vector3( self.vertices[ (self.quads[i+1]*3) ],
> > self.vertices[ (self.quads[i+1]*3)+1 ],
> > self.vertices[ (self.quads[i+1]*3)+2 ] )
>
> > p3 =Vector3( self.vertices[ (self.quads[i+2]*3) ],
> > self.vertices[ (self.quads[i+2]*3)+1 ],
> > self.vertices[ (self.quads[i+2]*3)+2 ] )
>
> > v1 = p1 - p2
> > v2 = p2 - p3
> > v1.normalize()
> > v2.normalize()
>
> > cross = v1.cross(v2)
> > cross.normalize()
>
> > self.quad_normals.extend( [ cross.x, cross.y, cross.z ] )
>
> It seems to me that you're only creating one normal for every four
> quad indices. There needs to be one normal for every vertex, and
> there's no correspondence here at the moment.
>
> Alex.
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