LHcoord and RHcoord coord collada

Graphics and GPU Programming Programming

Started by giugio January 10, 2009 12:30 PM

11 comments, last by giugio 15 years, 3 months ago

246

Author

January 10, 2009 12:30 PM

Hy. I'm created a collada importer , now i must apply the transformation of the node scene for the meshes in my file. I read about the directx is a RhCoord system , so i flip the triangles with this function:


for (pos =0;pos < CountIndexes/3 ;pos ++ )
{
   int swap = m_CurrMeshIndexes[pos * 3 + 1];
   m_CurrMeshIndexes[pos * 3 + 1] = m_CurrMeshIndexes[pos * 3 + 2];
   m_CurrMeshIndexes[pos * 3 + 2] = swap;

}

is sufficent to transform to a lhcoord? And the transform matrix that use is calculate with: dxMAtrix = dxTranslateParent *dxRotate * scale; is correct? and.. i read this :

Quote: * Flip the order of triangle vertices so that the system traverses them clockwise from the front. In other words, if the vertices are v0, v1, v2, pass them to Direct3D as v0, v2, v1. * Use the view matrix to scale world space by -1 in the z-direction. To do this, flip the sign of the _31, _32, _33, and _34 member of the D3DMATRIX structure that you use for your view matrix.

how i scale hte view matrix by -1? or flip the sign of 31 32 33 ecc..? THanks. [Edited by - giugio on January 10, 2009 1:16:22 PM]

giugio

246

Author

January 11, 2009 05:39 AM

nobody?

CableGuy

1,335

January 11, 2009 05:48 AM

Clicky?

giugio

246

Author

January 11, 2009 06:10 AM

i do this:

D3DXVECTOR3 pos(0.0f, 0.f,5.0f);	D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);	D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);	D3DXMATRIX V;	D3DXMatrixLookAtLH(		&V,		&pos,		&target,		&up);		D3DXMatrixScaling(&V,0,0,-1);		Device->SetTransform(D3DTS_VIEW, &V);	D3DXMATRIX dxMat;

is correct?
Thanks.

CableGuy

1,335

January 11, 2009 06:28 AM

D3DXMatrixLookAtLH, D3DXMatrixScaling will generate a new matrix, overriding the old one. To apply them both you would have to multiply them.

giugio

246

Author

January 11, 2009 06:46 AM

Now i'm see nothing
i'm a little frustrated, this is the code , where i do the mistake?

D3DXVECTOR3 pos(0.0f, 0.f,5.0f);	D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);	D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);	D3DXMATRIX V;	D3DXMatrixLookAtLH(		&V,		&pos,		&target,		&up);		D3DXMATRIX V1;	D3DXMatrixIdentity(&V1);	D3DXMatrixScaling(&V1,0,0,-1);	V*=V1;	Device->SetTransform(D3DTS_VIEW, &V);	D3DXMATRIX dxMat;	/*D3DXMatrixIdentity(&dxMat);	D3DXMatrixScaling(&dxMat,1,1,-1); 	Device->SetTransform(D3DTS_VIEW,&dxMat);*/		D3DXMATRIX proj;	D3DXMatrixPerspectiveLH(			&proj,			D3DX_PI * 0.5f, // 90 - degree			(float)Width / (float)Height,			1.0f,			10000.0f);	Device->SetTransform(D3DTS_PROJECTION, &proj);thanks again

CableGuy

1,335

January 11, 2009 08:45 AM

        D3DXMATRIX V;	D3DXMatrixLookAtLH(		&V,		&pos,		&target,		&up);		D3DXMATRIX V1,result;	D3DXMatrixScaling(&V1,0,0,-1);	D3DXMatrixMultiply(result,V,V1);        Device->SetTransform(D3DTS_VIEW, &result);        ...

Not tested. Also note that D3DXMatrixLookAtLH will generate a left hand coordinate system so it is possible you can skip the scaling part...
And out of curiosity I'm starting to implement a Collada importer myself, so do you have a good description or source on how to do it other than the Specs?

giugio

246

Author

January 11, 2009 10:28 AM

I read this :
http://msdn.microsoft.com/en-us/library/bb204853(VS.85).aspx
says that the order of the triangles must flipped(i do this)

and :

Quote:Use the view matrix to scale world space by -1 in the z-direction. To do this, flip the sign of the _31, _32, _33, and _34 member of the D3DMATRIX structure that you use for your view matrix.

when i apply a scale to -1 to the view matrix i see nothing!

but the transform must do to the view or the world matrix?

And, is the same use D3DXMatrixMultiply or the * operator?
Thanks.

CableGuy

1,335

January 11, 2009 12:22 PM

Quote:
* Use the view matrix to scale world space by -1 in the z-direction. To do this, flip the sign of the _31, _32, _33, and _34 member of the D3DMATRIX structure that you use for your view matrix.

As it says you also need to negate _34. Just flip the signs of the matrix components.

view._31=-view._31;view._32=-view._32;view._33=-view._33;view._34=-view._34;

EDIT: scaling by -1 will also flip _34... Try disabling back-face culling and see if this helps.

giugio

246

Author

January 11, 2009 01:24 PM

but this transformation must be apply at definition of the view (the camera)or always on each transform?
And how find the mesh in the word after this transform ? i don't see nothing!

and i not understand if is the same thing set the view matrix(that i presume is a d3dxmatrix but i can't find it)to a value or transform it with a matrix

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