gluLookat replacement

Graphics and GPU Programming Programming OpenGL

Started by mixmaster December 30, 2011 04:30 AM

7 comments, last by mixmaster 12 years, 3 months ago

373

Author

December 30, 2011 04:30 AM

Before I start, YES I have read lots of posts and code examples but I'm still stuck :-)

Here is my replacement code for gluLootat()



void lsMatrix4x4::LookAt( const lsVector3& eyePosition, const lsVector3& lookAt, const lsVector3& upVector )

{

lsMath math;

lsVector3 e, l, u;

lsVector3 forward, side, up;

lsMatrix4x4 matrix2, mat2;



e = eyePosition;

l = lookAt;

u = upVector;



// make sure up is normalized

up = upVector;

up.normalize();

// forward vector

forward = l - e;

forward.normalize();

// side vector

side = math.Cross( forward, up );

side.normalize();

// recalc up vector

up = math.Cross( forward, side );

up.normalize();





matrix2.matrix[0] = side.x;

matrix2.matrix[4] = side.y;

matrix2.matrix[8] = side.z;



matrix2.matrix[1] = up.x;

matrix2.matrix[5] = up.y;

matrix2.matrix[9] = up.z;



matrix2.matrix[2] = -forward.x;

matrix2.matrix[6] = -forward.y;

matrix2.matrix[10] = -forward.z;



mat2 *= matrix2;

mat2.TranslateMatrix( -e.x, -e.y, -e.z );



*this = mat2;

}

And here is the output from both OpenGL and my engine.



Camera Matrix : FPS_Camera

Matrix : OpenGL

-1 0 0 6.54721e-07

0 1 0 -1.76

0 0 -1 2.76058e-05

0 0 0 1

Matrix : vortxGE

-1 0 0 -6.54721e-07

0 -1 0 -1.76

0 0 -1 -2.76058e-05

0 0 0 1

I'm bashing my head against a wall, LOL.. It looks like a simple fix.

Any ideas anyone?

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

mixmaster

373

Author

December 30, 2011 06:09 AM

And here's another example of a test app.



cout << endl;

cout << "*********************************************************" << endl;

cout << "** Matrix Test " << endl;

cout << "*********************************************************" << endl;



lsMatrix4x4 mat;

lsVector3 eye, look, up;

GLfloat glmat[16];

lsOpenGL *ogl = vortxge->getCdl()->getOpengl();



// Identity

// OpenGL

glMatrixMode( GL_MODELVIEW );

glLoadIdentity();

glGetFloatv( GL_MODELVIEW_MATRIX, glmat );

ogl->DisplayMatrix4( glmat, "OpenGL: Identity" );



// vortxGE Matrix

ogl->DisplayMatrix4( mat.matrix, "vortxGE: Identity" );





// LookAt

// OpenGL

glLoadIdentity();

gluLookAt( 0,0,-10.0, 0,0,0, 0,1,0 );

glGetFloatv( GL_MODELVIEW_MATRIX, glmat );

ogl->DisplayMatrix4( glmat, "OpenGL: LookAt" );



// vortxGE LookAt

mat.LoadIdentity();

eye = lsVector3( 0, 0, -10.0 );

look = lsVector3( 0, 0, 0 );

up = lsVector3( 0, 1, 0 );

mat.LookAt( eye, look, up );

ogl->DisplayMatrix4( mat.matrix, "vortxGE: LookAt" );

And the output. I took the old SGI code as an example for LookAt.. hmmmmmmm.



*********************************************************

** Matrix Test

*********************************************************

Matrix : OpenGL: Identity

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

Matrix : vortxGE: Identity

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

Matrix : OpenGL: LookAt

-1 0 0 0

0 1 0 0

0 0 -1 -10

0 0 0 1

Matrix : vortxGE: LookAt

-1 0 0 0

0 -1 0 0

0 0 -1 10

0 0 0 1

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

mixmaster

373

Author

December 30, 2011 06:13 AM

Could this be because the old SGI code was Left-Handed and now OpenGL is Righ-Handed ???? Help :-)

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

doesnotcompute

262

December 30, 2011 08:06 AM

This is my LookAt function. I think I started from the Mesa implementation originally. My matrix class is row-major so that's why everything is transposed from you. I have to pass transpose=true to glUniformMatrix4fv because of this.



INLINE static void CreateLookAt(Vector3 const & position, Vector3 const & target, Vector3 const & upVector, Matrix & result)

{

  Vector3 forward;

  Vector3::Subtract(target, position, forward);

  forward.Normalize();



  Vector3 right;

  Vector3::Cross(forward, upVector, right);

  right.Normalize();



  Vector3 up;

  Vector3::Cross(right, forward, up);

  up.Normalize();  



  result.elements[0] = right.X;

  result.elements[1] = right.Y;

  result.elements[2] = right.Z;



  result.elements[4] = up.X;

  result.elements[5] = up.Y;

  result.elements[6] = up.Z;



  result.elements[8] = -forward.X;

  result.elements[9] = -forward.Y;

  result.elements[10] = -forward.Z;



  result.elements[12] = 0.0f;

  result.elements[13] = 0.0f;

  result.elements[14] = 0.0f;



  result.elements[3] = -Vector3::Dot(right,position);

  result.elements[7] = -Vector3::Dot(up,position);

  result.elements[11] = Vector3::Dot(forward,position);  

  result.elements[15] = 1.0f;

}

mixmaster

373

Author

December 30, 2011 08:46 AM

This is my LookAt function. I think I started from the Mesa implementation originally. My matrix class is row-major so that's why everything is transposed from you. I have to pass transpose=true to glUniformMatrix4fv because of this.

INLINE static void CreateLookAt(Vector3 const & position, Vector3 const & target, Vector3 const & upVector, Matrix & result) { Vector3 forward; Vector3::Subtract(target, position, forward); forward.Normalize(); Vector3 right; Vector3::Cross(forward, upVector, right); right.Normalize(); Vector3 up; Vector3::Cross(right, forward, up); up.Normalize(); result.elements[0] = right.X; result.elements[1] = right.Y; result.elements[2] = right.Z; result.elements[4] = up.X; result.elements[5] = up.Y; result.elements[6] = up.Z; result.elements[8] = -forward.X; result.elements[9] = -forward.Y; result.elements[10] = -forward.Z; result.elements[12] = 0.0f; result.elements[13] = 0.0f; result.elements[14] = 0.0f; result.elements[3] = -Vector3::Dot(right,position); result.elements[7] = -Vector3::Dot(up,position); result.elements[11] = Vector3::Dot(forward,position); result.elements[15] = 1.0f; }

Thanks doesnotcompute

It might be easier using dot products then MultMatrix, thank you so much for your reply. I'll give it a try soon.

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

shacktar

1,512

December 31, 2011 06:13 AM

// recalc up vector up = math.Cross( forward, side );

It looks like you've reversed this cross product. forward x side will get you the down vector using the right-hand rule. Try doing side x forward and see if that fixes the issue.

mixmaster

373

Author

January 03, 2012 05:43 PM

WOW !! I did so many things wrong with this it would be hard to explain how I fixed everything..

In short I had matrix calcs doubling up and rotation matrix mixed into my translation matrix. I must of had a brain fade during my rewrite.

All fixed now, thanks for your responces :-) P.S. ignore the code above its wring in so many ways. LOL.

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

mixmaster

373

Author

January 03, 2012 05:45 PM

[quote name='Lee Stripp' timestamp='1325219444' post='4898045']
// recalc up vector up = math.Cross( forward, side );

It looks like you've reversed this cross product. forward x side will get you the down vector using the right-hand rule. Try doing side x forward and see if that fixes the issue.
[/quote]

Yep, I was at that point where I was trying anything. Code got messy, I didn't need to recalc the Up vector :-)

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

mixmaster

373

Author

January 03, 2012 08:04 PM

Update for anyone interested.

Here's my working code



void lsMatrix4x4::LookAt( const lsVector3& eyePosition, const lsVector3& lookAt, const lsVector3& upVector )

{

lsMath math;

lsVector3 e, l, u;

lsVector3 forward, side, up;

lsMatrix4x4 rotmat, transmat;



e = eyePosition;

l = lookAt;

u = upVector;



// make sure up is normalized

up = upVector;

up.normalize();

up.debug( "up: " );

// forward vector

forward = l - e;

forward.normalize();

forward.debug( "forward: " );

// side vector

side = math.Cross( forward, up );

side.normalize();

side.debug( "side: " );



rotmat.matrix[0] = side.x;

rotmat.matrix[4] = side.y;

rotmat.matrix[8] = side.z;



rotmat.matrix[1] = up.x;

rotmat.matrix[5] = up.y;

rotmat.matrix[9] = up.z;



rotmat.matrix[2] = -forward.x;

rotmat.matrix[6] = -forward.y;

rotmat.matrix[10] = -forward.z;



transmat.TranslateMatrix( -e.x, -e.y, -e.z );



*this *= transmat * rotmat;

}

And the output it produces



Matrix : lsNode: Camera

[ 1 ]   [ 0 ]   [ 0 ]   [ 0 ]  

[ 0 ]   [ 1 ]   [ 0 ]   [ 0 ]  

[ 0 ]   [ 0 ]   [ 1 ]   [ -10 ]  

[ 0 ]   [ 0 ]   [ 0 ]   [ 1 ]  

up:  Vector(0,1,0)

forward:  Vector(0,0,1)

side:  Vector(-1,0,0)

Matrix : Camera ViewMatrix:

[ -1 ]   [ 0 ]   [ 0 ]   [ 0 ]  

[ 0 ]   [ 1 ]   [ 0 ]   [ 0 ]  

[ 0 ]   [ 0 ]   [ -1 ]   [ 10 ]  

[ 0 ]   [ 0 ]   [ 0 ]   [ 1 ]

I hope this will help someone avoid the pain I went through :-)

Cheers

Lee

Code is Life
C/C++, ObjC Programmer, 3D Artist, Media Production

Website : www.leestripp.com
Skype : lee.stripp@bigpond.com
Gmail : leestripp@gmail.com

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