Points disappear when glScaling....

[Uther_Pendragon]

Hi,

I'm writing a modeling program, in this program I draw points to display fe. selected points.

This works fine on my machine and some others but when I tested it on a PII Linux machine and on a portable with W98 the drawing gets messed-up when zooming.

For this zooming I always use glScale( );


What could be the problem here ?

Is this purely related to the video-drivers or did I forget something ?

Code to draw points :
======================

for (int i=0; i < nrPoints; ++i )
{
if(!data[ ss->directIndex[i] ]->isFlag(a_iFlag))
continue;
}

glBegin( GL_POINTS );

glVertex3d( data[ ss->directIndex[i] ]->x,
data[ ss->directIndex[i] ]->y,
data[ ss->directIndex[i] ]->z );

glEnd();

}

Code to zoom :
======================
glScalef( viewer->zf, viewer->zf, viewer->zf );

[Deiussum]

Maybe they are disappearing behind your far clip plane.

[Uther_Pendragon]

I'm not using clipping planes at this moment...

Could it be that clipping plane defaults are different on different OpenGL implementations ???

[NeoTuri]

Originally posted by Uther_Pendragon:
I'm not using clipping planes at this moment...

Could it be that clipping plane defaults are different on different OpenGL implementations ???

Yes, OpenGL defaults a near clipping plane (for integrity purposes) but I'm not sure it enforces the far clipping plane. I imagine that is does, but the point is to control your points so that they inhabit your view frustrum.

You can either change the far clipping plane in your projection functions (e.g. glOrtho, glFrustrum) or reduce the size of your units (i.e. 1unit=1m to 1unit=10m).

[Deiussum]

Originally posted by Uther_Pendragon:
I'm not using clipping planes at this moment...

Could it be that clipping plane defaults are different on different OpenGL implementations ???

Not using clipping planes?!? You are saying you don't use ANYTHING to setup your projection matrix? (gluPerspective, glFrustum, glOrtho, etc.)

If that is the case, I would definitely setup your projection matrix before doing anything else.

[Uther_Pendragon]

Sorry, I meanth no 'additional' clipping planes ;-)

[Uther_Pendragon]

I've set the clipping planes to :

near = 0.001f;
far = 10000.0f;

... still the same problem....

[NeoTuri]

Originally posted by Uther_Pendragon:

I've set the clipping planes to :

near = 0.001f;
far = 10000.0f;

... still the same problem....

Are you able to see them without using glScalef() ?

[Deiussum]

When do you call the glScale function? Do you use anything like gluLookAt, glRotate, or glTranslate? If so, in what order are all these in relation to your glScale?

[zed]

shot in the dark
perhaps u have lighting enabled, and scaling is causing your normals to go haywire.
note im not to sure if points have normals but its worth a shot