# OpenGL Drawing Mesh

## Recommended Posts

I'm trying to draw the mesh ontop of my world objects in OpenGL, but I'm having problems. If I turn on Depth testing, it draws like I want, but the mesh lines are "inside" many of the polygons, resulting in a mesh that fades in and out. If I turn off depth testing, the lines look perfect but I can see through meshes, which obviously gets very confusing very fast. How do I do this?

##### Share on other sites
its not 100% clear what u want
eg possible solutions
A/ use various glDepthRanges(..)
B/ clear the depth buffer before u draw the mesh
C/ use polygon offset

##### Share on other sites
I'm still somewhat new to OpenGL.

Basically I want to draw the wire mesh on top of the polygons being rendered. If I just draw the wireframe as usual, it gets variously obscured by by the poly mesh, resulting in a dulled wireframe that's not as distinct as I'd like.

Like you can show in a modeller such as Maya.

##### Share on other sites
If you're having the same problem that I did, I could draw plain wireframes ok, but if I drew them with a colored solid and then a wireframe, the wireframe wouldn't look right with depth testing on. Try this before you draw your solid version.

glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glEnable(GL_POLYGON_OFFSET_FILL);
glPolygonOffset(1.0, 1.0);

That should take care of your problem. The seeing through the meshes problem you are talking about can be fixed with a call to glEnable(GL_CULL_FACE); Opengl defaults to counter clockwise wound polygons, and will not draw clockwise wound polygons(the back facing ones) with this option enabled. But I'm guessing your overall scene is going to need depth testing on at some point.

##### Share on other sites
Your first fix is definately an improvement. What exactly is it doing :P?

##### Share on other sites
It's telling opengl that when you draw the filled polygon and it's time to update the depth buffer, that instead of putting the actual depth of the polygon it uses an offset of one more depth unit than it normally would. Then when you just draw the lines for the wireframe which would normally have the same depth values as the filled polygon(but now they don't since you used offset fill) they now appear how they should. Make sure you disable offset fill when your done using it too.

Here's where I originally learned to do it, click here, it's from the Red Book, you should definitely check it out.

[Edited by - Disgruntled Gamer on May 22, 2006 3:58:04 PM]

## Create an account

Register a new account

• ### Forum Statistics

• Total Topics
627701
• Total Posts
2978705
• ### Similar Content

• A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

-What I'm using:
C++;. Since im learning this language while in college and its one of the popular language to make games with why not.     Visual Studios; Im using a windows so yea.     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.
-Questions
Knowing what we want in the engine what should our main focus be in terms of learning. File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code. Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?

• Both functions are available since 3.0, and I'm currently using glMapBuffer(), which works fine.
But, I was wondering if anyone has experienced advantage in using glMapBufferRange(), which allows to specify the range of the mapped buffer. Could this be only a safety measure or does it improve performance?
Note: I'm not asking about glBufferSubData()/glBufferData. Those two are irrelevant in this case.
• By xhcao
Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness.
• By cebugdev
hi guys,
are there any books, link online or any other resources that discusses on how to build special effects such as magic, lightning, etc. in OpenGL? i mean, yeah most of them are using particles but im looking for resources specifically on how to manipulate the particles to look like an effect that can be use for games,. i did fire particle before, and I want to learn how to do the other 'magic' as well.
Like are there one book or link(cant find in google) that atleast featured how to make different particle effects in OpenGL (or DirectX)? If there is no one stop shop for it, maybe ill just look for some tips on how to make a particle engine that is flexible enough to enable me to design different effects/magic
let me know if you guys have recommendations.
• By dud3
How do we rotate the camera around x axis 360 degrees, without having the strange effect as in my video below?
Mine behaves exactly the same way spherical coordinates would, I'm using euler angles.
Tried googling, but couldn't find a proper answer, guessing I don't know what exactly to google for, googled 'rotate 360 around x axis', got no proper answers.

References:
Code: https://pastebin.com/Hcshj3FQ
The video shows the difference between blender and my rotation:

• 21
• 14
• 12
• 10
• 12