Camera Rotation

glProgram · 2001-09-23T20:43:59

Can anybody tell me a good way to do camera rotation using gluLookAt()? All tutorials I''ve seen did a terrible job and didn''t work. Also no one ever really explains gluLookAt(). Also it would help if it were done with the camera''s Position X, Y, Z and Look X, Y, Z, and Up X, Y, Z. And if possible can you include how to move in the direction the camera is looking at. Thanks.

Graphics and GPU Programming Programming

Started by glProgram September 04, 2001 08:25 PM

27 comments, last by glProgram 22 years, 7 months ago

DeathWish

122

September 17, 2001 11:29 AM

Personally I''ve never used gluLookAt(), I hardly use the glu library except for mipmaps and quadratic shapes. You could try it using just the standard glRotatef() and glTranslatef(), or you could do what I do in my basic 3D engine and translate all the co-ordinates by generating my own translation matrix and keeping the camera at 0,0,0.

Or, one thing you could try:

glLoadIdentity();
glPushMatrix();
// translate, rotate, render
glPopMatrix();

I''m not too sure about it though, so I may be totally wrong on the matrix push/pops... I hardly use them

(BTW, if you want to use your own translation matrix then I''m more than happy to help you if you don''t know how.)

DeathWish

DeathWish

122

September 17, 2001 11:31 AM

Another thought... you could try reverse transforming your camera. (Transform -x -y -z, rotate -z -y -x)

DeathWish

Oluseyi

2,123

September 17, 2001 12:09 PM

quote:Original post by Anonymous Poster
inline float cosd(float p_angle)
{
return cos(p_angle * (3.141592654 / 180));
}

wouldnt it be better to precalculate 3.141592654 / 180
this would speed the function up!

The compiler will do that for you. The only real optimization with sine and cosine is to precalculate them (they are horrendously expensive functions):

  float Sine[360], Cosine[360];const float M_PI = 3.141592654;void CreateTrigLUTs( void ){  for( int i = 0; i < 360; i++ )  {    Sine[i] = (float)sin( i * M_PI / 180 );    Cosine[i] = (float)cos( i * M_PI / 180 );  }}

EDIT: i as array index.

Edited by - Oluseyi on September 17, 2001 1:10:35 PM

zedzeek

529

September 17, 2001 03:49 PM

using a LUT for a couple of sin''s cos''s will most likely be slower than using sin(A).
the LUT really is only benificial when youre doing heaps of sin''s at a time

http://members.xoom.com/myBollux

Captain Courgette, eat more veg

glProgram

122

Author

September 17, 2001 06:46 PM

Hey, none of that was really a reply to my last post.
Does anybody got any clues about the distance problem?

DeathWish

122

September 18, 2001 12:04 PM

Ok, I''ve got an idea:

glMatrixMode(GL_PERSPECTIVE);
gluPerspective(...);

glMatrixMode(GL_MODELVIEW);
gluLookAt(...);
glBegin(...);
...
glEnd();

glProgram

122

Author

September 18, 2001 03:11 PM

Actually I believe it''s GL_PROJECTION, not GL_PERSPECTIVE.
And that didn''t help at ALL.
You can''t use gluLookAt() in the GL_MODELVIEW matrix.
And I already do use gluPerspective in GL_PROJECTION and it can only be used in that matrix.

zedzeek

529

September 18, 2001 05:27 PM

>>There''s still that problem with distance.(You have to be REAL close)(And also note that when rotating the camera I can
see that object wireframes will get cut off near the camera<<

decrease your near planes depth value + increase the far planes value
in gluPerspective they are the 3rd+4th variable

http://members.xoom.com/myBollux

Captain Courgette, eat more veg

DeathWish

122

September 19, 2001 10:20 AM

I meant GL_PROJECTION... sorry I can''t help you then....

glProgram

122

Author

September 19, 2001 03:07 PM

zedzeek, that is very obvious and it keeps getting repeated here. I have tried that 3 times! I''ve tried a near distance
of 0.0f and a far distance of 100000.0f, no effect.

Camera Rotation

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