looking and moving up and down(pitch) using glRotate()

Crossbow · 06-13-2002, 09:28 PM

I have a OpenGL program that is like a space simulator. I have the thing correctly turning and flying straight, but things start to get difficult when I try to look up and down. To look up and down, or pitch, I have the program increase pitch by one is down and decrease if up, when the up or down key is pressed. Then, in the draw function, I have the glRotatef function rotate on the x axis up and down according to pitch. Like:

Code:

glRotatef(pitch,1.0f,0,0);

And this works fine if I am facing along the x axis(0(360) or 180 degrees), but say I face 90 degrees on the z axis, the screen rotates around in a circle. I hope you follow me on this. I can't figure out how to fix this, so any suggestions would be great. Thanks!

no-one · 06-14-2002, 03:12 PM

if i get what your saying correctly, it's because at 90 degrees you should be rotating on the z axis to go up and down... the way you are attempting to do this is fairly complicated,
you could try

Code:

void gluLookAt(
  GLdouble eyex,      
  GLdouble eyey,      
  GLdouble eyez,      
  GLdouble centerx,   
  GLdouble centery,   
  GLdouble centerz,   
  GLdouble upx,       
  GLdouble upy,       
  GLdouble upz        
);

eyex, eyey, eyez 
The position of the eye point. 
centerx, centery, centerz 
The position of the reference point. 
upx, upy, upz 
The direction of the up vector.

and/or look into vector math and trigonomotry...

Crossbow · 06-14-2002, 09:53 PM

Ok, I looked up that function and it will work, but there is one thing I don't know about it, and that is the up vector. When I change the values it doesn't seem to have any effect. What does it do?

no-one · 06-15-2002, 12:17 AM

it specifies the up "Vector" technically its the up Axis

so if you use (0.0,1.0,0.0) then positive y is up
if you use (0.0,-1.0,0.0) negative y is up
if you us (1.0,0.0,0.0) positive x is up

get it?

using decimal points wont really change anything...

06-13-2002, 09:28 PM	#1
Crossbow Registered User Join Date: Nov 2001 Posts: 162	looking and moving up and down(pitch) using glRotate() I have a OpenGL program that is like a space simulator. I have the thing correctly turning and flying straight, but things start to get difficult when I try to look up and down. To look up and down, or pitch, I have the program increase pitch by one is down and decrease if up, when the up or down key is pressed. Then, in the draw function, I have the glRotatef function rotate on the x axis up and down according to pitch. Like: Code: glRotatef(pitch,1.0f,0,0); And this works fine if I am facing along the x axis(0(360) or 180 degrees), but say I face 90 degrees on the z axis, the screen rotates around in a circle. I hope you follow me on this. I can't figure out how to fix this, so any suggestions would be great. Thanks!
Crossbow is offline

06-14-2002, 03:12 PM	#2
no-one Has a Masters in B.S. Join Date: Aug 2001 Posts: 2,267	if i get what your saying correctly, it's because at 90 degrees you should be rotating on the z axis to go up and down... the way you are attempting to do this is fairly complicated, you could try Code: void gluLookAt( GLdouble eyex, GLdouble eyey, GLdouble eyez, GLdouble centerx, GLdouble centery, GLdouble centerz, GLdouble upx, GLdouble upy, GLdouble upz ); eyex, eyey, eyez The position of the eye point. centerx, centery, centerz The position of the reference point. upx, upy, upz The direction of the up vector. and/or look into vector math and trigonomotry... __________________ ADVISORY: This users posts are rated CP-MA, for Mature Audiences only.
no-one is offline

06-14-2002, 09:53 PM	#3
Crossbow Registered User Join Date: Nov 2001 Posts: 162	Ok, I looked up that function and it will work, but there is one thing I don't know about it, and that is the up vector. When I change the values it doesn't seem to have any effect. What does it do?
Crossbow is offline

06-15-2002, 12:17 AM	#4
no-one Has a Masters in B.S. Join Date: Aug 2001 Posts: 2,267	it specifies the up "Vector" technically its the up Axis so if you use (0.0,1.0,0.0) then positive y is up if you use (0.0,-1.0,0.0) negative y is up if you us (1.0,0.0,0.0) positive x is up get it? using decimal points wont really change anything... __________________ ADVISORY: This users posts are rated CP-MA, for Mature Audiences only.
no-one is offline

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