# Camera Roation

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Ok I'm having some trouble w\ my camera rotation. I know there are camera classes out there but I want to learn this. This cam will have no lateral roation or movement, just side to side rotation and forward and back translation. So this is what I got: For Input: if (keys[VK_UP]) // Is The Up Arrow Being Pressed? { ztranslate += sin((float)yangle) * .005; xtranslate += cos((float)yangle) * .005; } if (keys[VK_DOWN]) // Is The Down Arrow Being Pressed? { ztranslate -= sin((float)yangle) * .005; xtranslate -= cos((float)yangle) * .005; } if (keys[VK_RIGHT]) // Is The Right Arrow Being Pressed? { yangle += .01; } if (keys[VK_Left]) // Is The Left Arrow Being Pressed? { yangle -= .01; } This is what I have for the actual movement and rotation: // Move Camera glRotatef(yangle, 0.0f, 1.0f, 0.0f); glTranslatef(xtranslate, 0.0f, ztranslate); As you can see I leave the Y alone. Now the rotation is working great. The translation is the problem. The idea I have is I know the angle (yangle) of a right triangle. So I can use sin to get the Opp side which should b my Z cord and I can use Cos to get my Adj side which should b my X cord. then I multiplay by .005 so that I control the "speed" or distance of the translation. This just give me the point I want to move to right? So then I just plug that point into my glTranslate function and it just go, but it doesnt... Here take a look at the unpreditable responses: http://www.talentopoly.com/adam/UPLOADS/cpp/WinMain.exe it's not a virus, i'm not competent enough to program a virus, so dont worry.

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Yeah but, where's your "look at" function...?

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I'm not using gluLookAt(); I'm doing the rotations and translations manual.

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no ideas any one? Is my math wrong, is the application of the answer to the translation wrong? Plz I'm been working on this for hours and hours!

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But... but... see, what ARE you rotating and translating? Do you see the problem?

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Well... the world. Everything, those come before i draw anything.
Take a look @ that sample prog I linked to, it almost works. It's just the direction of the translation is screwed up some times.

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Okay, maybe the camera idea is a little vague. As far as I know there is no actual camera in OpenGL. It's a concept, nothing more.

Basically, according to your code, you aren't switching your matrix mode to projection. Therefore just calling rotate and translate out in the middle of nowhere will simply rotate and translate the last thing in the matrix stack, which could be anything at all, and not even the projection matrix.

Then again your code sample looks cut-n-pasted, so I can't tell if you're doing that or not.

What have you got against gluLookAt, anyway? ;)

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Hey there,

Try this
if (keys[VK_UP]) // Is The Up Arrow Being Pressed?{ztranslate -= sin((float)yangle) * .005;xtranslate += cos((float)yangle) * .005;}if (keys[VK_DOWN]) // Is The Down Arrow Being Pressed?{ztranslate += sin((float)yangle) * .005;xtranslate -= cos((float)yangle) * .005;}

The do your

glRotatef(yangle, 0.0f, 1.0f, 0.0f);glTranslatef(xtranslate, 0.0f, ztranslate);

If you walk the wrong way, then switch all of your += and -= around.

If you check out the law of sines, you'll see what you're doing wrong. Let me know if this helps!

PS: This is a great math tutorial to get this stuff sorted out.
Clicky

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hehe i dont have anything against gluLookAt what I can't figure out is how to set the direction to look in correctly every time.

Ur right I didnt post the full code here, i coppied in snippets, but it's all my code if thats what u mean.

I'm not rotating the Projection Matrix. I'm rotating the modle view matrix as far as I know... I guess thats a problem huh...

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Quote:
 Original post by Wavesonicshehe i dont have anything against gluLookAt what I can't figure out is how to set the direction to look in correctly every time.Ur right I didnt post the full code here, i coppied in snippets, but it's all my code if thats what u mean.I'm not rotating the Projection Matrix. I'm rotating the modle view matrix as far as I know... I guess thats a problem huh...

No, you're going to want to use the ModelView matrix.

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Ok I just tried your code and it seems to have about the same effect look:

It work for some directions (read: angles) but gets all screwy when u rotate to other angles.

Also could U explain the logic behind the changes u made 2 the math code there? I really wanna learn this.

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Do you want to post all of your code?

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Ya sure I'll post the code, its incredibly dirty right now b/c i've been commenting out stuff and working around things and u'll see... once i get this working and i know what i need i'll clean it up.

WinMain (win32 entry point):
Here you'll want to look at line 183 for my render calls to the OpenGLOps Object called OGLO:

My OpenGL Operations Included into WinMain:
Here you'll want to look at SetUpFrame() on line 107:

Just my class declaration...

[Edited by - Wavesonics on August 4, 2004 1:42:30 PM]

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Ok I must be close b/c I found this math code in a tutorial with a working camera:

if (keys[VK_UP])
{
}

Now it looks like hes converting degrees to radians by multiplying degrees (heading) by pi / 180. Besides that my math and his math is exactly the same.

Why would converting it to radians matter?

Then he takes the xpos and zpos and inverts them for the final translation:

GLfloat xtrans = -xpos;
GLfloat ztrans = -zpos;
glTranslatef(xtrans, ytrans, ztrans);

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Just looking through your code, it looks like you're not converting your angles into radians. C++'s sin and cos functions expect radians. Just multiply your angle by pi*180 to do that.

EDIT: WOOPS! Should have refreshed the page before posting... BTW, which compiler are you using?

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haha, um Dev C++ is my IDE, MinGW compiler.

Well that explains why hes converting to radians, thank you.

Now I plugged his code into my code and it still doesnt work... And I'm pretty sure I transfered it perfectly.

Aw 1 small thing, he stores yrot (rotation) and heading seperately. But I cant see why, as far as I can tell yrot is set = to heading, and is never changed. But heading is used for the translation calculations not yrot.

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jakem3s90 do u have icq or aim or something so maybe we could talk in real time?
ICQ: 39886687
MSN: wavesonics@hotmail.com

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Ok.. Here's a couple things to try

(I'm at work, so I can't really check it myself)

Restructure your render loop as such:

First, pull the glMatrixMode(GL_MODELVIEW) and the glLoadIdentity() calls from your render loop, stick them just before you start that loop.

Also, call glPushMatrix() before you call OGLO.RenderFrame() and a glPopMatrix() after.

Other than that, you're code looks good, it's hard to tell without really digging through it though.

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Quote:
 Original post by Wavesonicsjakem3s90 do u have icq or aim or something so maybe we could talk in real time?ICQ: 39886687AIM: JebradicYAHOO: JebradicMSN: wavesonics@hotmail.com

Just PM'd you my info...

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haha ok, so removing the ident matrix from the loop, its job is essentialy replaced by the push and pop of the matrix. Other wise things go all scewy.

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I only looked through the code briefly but it seems that you're not clearing the modelview matrix each time you call renderframe()? Additionally, the only thing I thought was wrong with your math is that you're not translating by the negation of your camera position; i.e., do glTranslatef(-x, 0, -z);

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Lol, in the time I read the code and made the post, jakem3s90 pretty much said what I was gonna :P

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Wouldn't clearing the modleview just be loading the ident matrix since the modelview matrix is already selected? And I just added in the - to the translation, just figured out why u want that hehe.

I gtg right now but I'll b working on this l8er today, thx for ur help everyone!

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Yea that's what I meant, glLoadIdentity() with it. You don't want transformations from last frame affecting this frame's matrix and compounding together into a mess.