4 replies to this topic

[maheshbinny]

Can somebody help me intilizarion of camera in OpenGL ES 2.0

I mean matrix calculation for Camera LookAt, Position and Up vector ?

Mahesh

[EngineCoder]

Here's my lookat() implementation:

void Matrix::makeLookAt( const Vec3& aEye, const Vec3& aCenter, const Vec3& aUp, float* aMatrix )
{
    assert( aMatrix );
    Vec3 forward = aCenter - aEye;
    forward.normalize();
   
    Vec3 right = forward.cross( aUp );
    right.normalize();
   
    const Vec3 up = right.cross( forward );
   
    aMatrix[ 0 ] = right.x;
    aMatrix[ 4 ] = right.y;
    aMatrix[ 8 ] = right.z;
    aMatrix[ 12 ] = 0;
   
    aMatrix[ 1 ] = up.x;
    aMatrix[ 5 ] = up.y;
    aMatrix[ 9 ] = up.z;
    aMatrix[13 ] = 0;
   
    aMatrix[ 2 ] = -forward.x;
    aMatrix[ 6 ] = -forward.y;
    aMatrix[10 ] = -forward.z;
    aMatrix[14 ] = 0;
   
    aMatrix[ 3 ] = aMatrix[ 7 ] = aMatrix[ 11 ] = 0.0f;
    aMatrix[15 ] = 1.0f;
    float translate[ 16 ];
    Matrix::identity( translate );
    translate[ 12 ] = -aEye.x;
    translate[ 13 ] = -aEye.y;
    translate[ 14 ] = -aEye.z;
   
    multiply( translate, aMatrix, aMatrix );
}

[clb]

In MathGeoLib float3x4 class, you can find an implementation of a LookAt matrix. The derivation is identical, up to translation, to the function float3x3::LookAt, and the code and documentation on how it is done is available here. This matrix will map from the local space of the object (object==camera in this case) to the world space, so for the camera, this mapping will be a View->World space mapping. To produce a World->View space mapping as is usually needed, take the inverse of the resulting matrix.

Edited by clb, 11 May 2012 - 11:44 AM.

[maheshbinny]

Here's my lookat() implementation:

void Matrix::makeLookAt( const Vec3& aEye, const Vec3& aCenter, const Vec3& aUp, float* aMatrix )
{
	assert( aMatrix );
	Vec3 forward = aCenter - aEye;
	forward.normalize();
  
	Vec3 right = forward.cross( aUp );
	right.normalize();
  
	const Vec3 up = right.cross( forward );
  
	aMatrix[ 0 ] = right.x;
	aMatrix[ 4 ] = right.y;
	aMatrix[ 8 ] = right.z;
	aMatrix[ 12 ] = 0;
  
	aMatrix[ 1 ] = up.x;
	aMatrix[ 5 ] = up.y;
	aMatrix[ 9 ] = up.z;
	aMatrix[13 ] = 0;
  
	aMatrix[ 2 ] = -forward.x;
	aMatrix[ 6 ] = -forward.y;
	aMatrix[10 ] = -forward.z;
	aMatrix[14 ] = 0;
  
	aMatrix[ 3 ] = aMatrix[ 7 ] = aMatrix[ 11 ] = 0.0f;
	aMatrix[15 ] = 1.0f;
	float translate[ 16 ];
	Matrix::identity( translate );
	translate[ 12 ] = -aEye.x;
	translate[ 13 ] = -aEye.y;
	translate[ 14 ] = -aEye.z;
  
	multiply( translate, aMatrix, aMatrix );
}

Thank you very much

[taby]

This may be helpful:
http://db-in.com/blog/2011/04/cameras-on-opengl-es-2-x/