# OpenGL GL_MODELVIEW and GL_PROJECTION

## Recommended Posts

Does it normally make any difference what you use the matrix GL_MODELVIEW or GL_PROJECTION for? For example, I use GL_PROJECTION for the prespective projection, but use GL_MODELVIEW for the direction and position of the camera. Can it normally work that way, or should I put those in the GL_PROJECTION matrix instead? I have to invert the 3x3 part with u, v and direction for some reason and I'm not sure it could be because of me using the wrong matrix in OpenGL.

##### Share on other sites
Quote:
 Original post by LodeDoes it normally make any difference what you use the matrix GL_MODELVIEW or GL_PROJECTION for?For example, I use GL_PROJECTION for the prespective projection, but use GL_MODELVIEW for the direction and position of the camera.Can it normally work that way, or should I put those in the GL_PROJECTION matrix instead? I have to invert the 3x3 part with u, v and direction for some reason and I'm not sure it could be because of me using the wrong matrix in OpenGL.
I'm not sure what you mean by inverting the 3x3 part, but whatever problem you're running into most likely has to do with something else (such as conflicting notational conventions) rather than which OpenGL matrix mode you're using.

The OpenGL matrix modes are intended to be used as their names suggest, more or less. The projection matrix is for transformation of geometry from view to clipping space, usually by way of a perspective or orthographic projection. The modelview matrix is for transformation of geometry from model to view space (therefore the camera/view transform most correctly goes in the modelview matrix).

I believe you can 'misuse' the different OpenGL matrices and still get correct results in some cases, but it's not advisable.

## Create an account or sign in to comment

You need to be a member in order to leave a comment

## Create an account

Sign up for a new account in our community. It's easy!

Register a new account

• ## Partner Spotlight

• ### Forum Statistics

• Total Topics
627676
• Total Posts
2978581
• ### Similar Content

• 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.
Thank you in advance!
• 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:

• By Defend
I've had a Google around for this but haven't yet found some solid advice. There is a lot of "it depends", but I'm not sure on what.
My question is what's a good rule of thumb to follow when it comes to creating/using VBOs & VAOs? As in, when should I use multiple or when should I not? My understanding so far is that if I need a new VBO, then I need a new VAO. So when it comes to rendering multiple objects I can either:
* make lots of VAO/VBO pairs and flip through them to render different objects, or
* make one big VBO and jump around its memory to render different objects.
I also understand that if I need to render objects with different vertex attributes, then a new VAO is necessary in this case.
If that "it depends" really is quite variable, what's best for a beginner with OpenGL, assuming that better approaches can be learnt later with better understanding?

• 11
• 12
• 10
• 12
• 22