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lid6j86's picture

Perspective

Posted Saturday, 26 May, 2012 - 14:22 by lid6j86 in

I keep seeing all these examples with gluPerspective, and I'm reading about gluPerspective, and that it is for 3d rendering (whereas ortho is for 2d rendering), but I can't seem to find the method anywhere. I've looked in a dozen places, including under GL., i've tried to find Glu, etc... and I can't find it. did OpenTK change how that works, or how to call it?

i saw something about setting up a frustrum or something... is that what it has switched to?

I'm ok on a 2d setting now for setting up the window but i'm having a heck of a time getting started on the 3d perspective.

one last question, does OpenTK default as a left handed or right handed coordinate system? (i prefer for it to be left handed)

Thanks.

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Showle1943's picture

Re: Perspective

Posted Sunday, 27 May, 2012 - 00:50 by Showle1943
lid6j86 wrote:

I keep seeing all these examples with gluPerspective, and I'm reading about gluPerspective, and that it is for 3d rendering (whereas ortho is for 2d rendering), but I can't seem to find the method anywhere. I've looked in a dozen places, including under GL., i've tried to find Glu, etc... and I can't find it. did OpenTK change how that works, or how to call it?

i saw something about setting up a frustrum or something... is that what it has switched to?

I'm ok on a 2d setting now for setting up the window but i'm having a heck of a time getting started on the 3d perspective.

one last question, does OpenTK default as a left handed or right handed coordinate system? (i prefer for it to be left handed)

Thanks.

I'm trying to find the same answer - have scoured dozens of sites but nothing. If you find an answer please let me know.

jrwatts's picture

Re: Perspective

Posted Monday, 28 May, 2012 - 07:31 by jrwatts

GLU is old and deprecated, but you can still access it, if you wish, with OpenTK.Compatibility.

Edit: Ignore the following sentence; I was half-asleep when typing it and completely wrong (see later comment for correct answer)!
I believe the preferred replacement for gluPerspective() is Matrix4.LookAt()...search for that on the forums and you'll find plenty of examples of how to use it.

Also, OpenGL is right-handed by default, but can easily be transformed for left-handed coordinates with GL.Scale(1.0, 1.0, -1.0) (you may need to swap your vertex winding, as well).

lid6j86's picture

Re: Perspective

Posted Sunday, 27 May, 2012 - 06:10 by lid6j86

I have vertex winding to counterclockwise.

i thought matrix4.lookat was for something different, i'll take a look

lid6j86's picture

Re: Perspective

Posted Sunday, 27 May, 2012 - 06:32 by lid6j86

Is there any way the admins can add to the documentation list on the site about Matrix4? seems like it's quite important as the basis for 3d perspective mode, etc...

jrwatts's picture

Re: Perspective

Posted Sunday, 27 May, 2012 - 20:24 by jrwatts

Gah, this is what happens when you try to answer questions while half-asleep! Sorry, Matrix4.LookAt() is, of course, the replacement for gluLookAt(), not gluPerspective()! Off the top of my head, I'm not sure what to use in place of gluPerspective() (although I vaguely recall this topic coming up before).

Edit: Did a search of the forums for gluPerspective, and found an alternate implementation in this thread: http://www.opentk.com/node/2050 (see the Glu.cs file attached to the second-to-last comment).

lid6j86's picture

Re: Perspective

Posted Monday, 28 May, 2012 - 01:24 by lid6j86

think i finally found it:

http://stackoverflow.com/questions/2417697/gluperspective-was-removed-in..., just needs translated.

anyone have any idea why gluperspective was depreciated from OpenGL? It seems like it was fairly easy to use and impliment, but they got rid of it in favor of forcing you to do it manually... was it causing too many errors of some sort?

jrwatts's picture

Re: Perspective

Posted Monday, 28 May, 2012 - 07:27 by jrwatts

http://stackoverflow.com/questions/1218449/opengl-whats-the-deal-with-de... (from the same site as your link) does a fairly good job of explaining why various functions (in particular, the whole fixed function pipeline) have been deprecated (in a nutshell, it's too hard to make sure new features work with the old stuff).

http://stackoverflow.com/questions/2079038/new-to-opengl-and-deprecation points to some tutorials that don't use the deprecated functions.

Really, I see no problem with just sticking with OpenGL 2.0 functionality and ignoring all the deprecation, if you're writing a simple program that doesn't need the latest features (it seems unlikely to me that hardware manufacturers will drop support for OpenGL 2.0 any time soon). (And I'm sure there are plenty of people on this forum who disagree with me!)

lid6j86's picture

Re: Perspective

Posted Monday, 28 May, 2012 - 12:45 by lid6j86

So 1 more question for now until a later time when I bug you all again:

I'm looking at this Matrix4 stuff, but there are a lot of things that look very similar.

For instance, what is the difference between Matrix4.CreatePerspectiveFieldofView and Matrix4.Perspective?

They both look like they have the same parameters, and they both have the same description

anyways, it might make sense to make a small dedicated tutorial to matrix4 and its possibilities/ some examples.