[Solved]View matrix from direction and position
Author
I'm attempting to create a view matrix from a d3dlight9 object. I have a position, and a direction vector.
Can I create a view matrix from this, assuming that (0.0, 1.0, 0.0) is up?
Thank you
[Edited by - PSS on February 25, 2009 10:01:02 AM]
You can use the unit-y vector as a starting point and you can then refine it to get a more accurate right and up vector:
if (Math.Abs(Vector3.Dot(Up, L)) < .5f){ R = Vector3.Cross(Up, L); U = Vector3.Cross(L, R);}else{ U = Vector3.Cross(L, Right); R = Vector3.Cross(U, L);}
Author
Thanks for the confirmation.
I tried the following before posting, though when rotating the light, the scene just moves very slightly in an almost circular fashion.
D3DXVECTOR3 tvUp( 0.0f, 1.0f, 0.0f );
D3DXMatrixLookAtLH( &m_viewMatrix, &tvLight.Position, &tvLight.Direction, &tvUp );
Note: This is calculating the camera's view matrix, and tvLight is a D3DLIGHT9 object
Should I be taking the light direction as the 'at' vector?
[Edited by - PSS on February 24, 2009 11:47:34 PM]
I tried the following before posting, though when rotating the light, the scene just moves very slightly in an almost circular fashion.
D3DXVECTOR3 tvUp( 0.0f, 1.0f, 0.0f );
D3DXMatrixLookAtLH( &m_viewMatrix, &tvLight.Position, &tvLight.Direction, &tvUp );
Note: This is calculating the camera's view matrix, and tvLight is a D3DLIGHT9 object
Should I be taking the light direction as the 'at' vector?
[Edited by - PSS on February 24, 2009 11:47:34 PM]
You're using a direction vector where you should have a target.
D3DXMatrixLookAtLH( pOut, pEye, pAt, pUp );
In your case, you're passing in pOut, pEye, pDir, pUp.
To compute pAt, just add your position and direction vectors to get a point along the line of your direction.
D3DXVECTOR3 at;
D3DXVec3Add( &at, &tvLight.Position, &tvLight.Direction );
D3DXMatrixLookAtLH(&m_viewMatrix, &tvLight.Position, &at, &tvUp);
Cheers!
D3DXMatrixLookAtLH( pOut, pEye, pAt, pUp );
In your case, you're passing in pOut, pEye, pDir, pUp.
To compute pAt, just add your position and direction vectors to get a point along the line of your direction.
D3DXVECTOR3 at;
D3DXVec3Add( &at, &tvLight.Position, &tvLight.Direction );
D3DXMatrixLookAtLH(&m_viewMatrix, &tvLight.Position, &at, &tvUp);
Cheers!
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