n00b question: getting rid of lines along edges of polygons

Member

Posts: 208
Joined: 2005.04

Post: #1

Jun 5, 2005 — 05:02 PM

So I decided to try my hand at OpenGL this morning...

I'm trying to display a cube and make it look as nice as possible (antialiasing == good). Unfortunately, I can't seem to get rid of some annoying artifacts. Here's a screenshot:

[Image: glcube.gif]

Why are those lines showing up?

Here's my code to set up the environment:

Code:

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glEnable(GL_BLEND);

glEnable(GL_POLYGON_SMOOTH);

glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST);

glEnable(GL_COLOR_MATERIAL);  

glEnable(GL_LIGHT0);

glEnable(GL_DEPTH_TEST);

glEnable(GL_LIGHTING);

And here's the code for drawing the cube:

Code:

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

gluLookAt(1,1,1,

          0,0,0,

          0,1,0);

glRotatef(20, 0, 1, 0);

glutSolidCube(0.5);

glFinish();

I'm doing this in Cocoa. In IB, I've set my NSOpenGLView subclass' attributes as follows:

Renderer: Best
Color/Alpha Buffer: Default
Depth Buffer: 16bit
Stencil Buffer: None
Accum. Buffer: None

My graphics card is an ATI Mobility Radeon 9200 (on an iBook G4).

Thanks

Andrew

arekkusu

Sage

Posts: 1,231
Joined: 2002.10

Post: #2

Jun 5, 2005 — 05:21 PM

Polygon smoothing relies on blending, and blending is incompatible with the depth buffer.

Read my earlier explanation. Also see this and this.

Andrew

Member

Posts: 208
Joined: 2005.04

Post: #3

Jun 5, 2005 — 05:57 PM

Thanks arekkusu!

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