looks like I got confused on my side. I realised I don't need a lookAt vector
but a position in space that the camera is "looking at".
a friend helped out and gave me this:
camMatrix = getWorldMatrix( camNode ) #USING IVANS FUNCTION
#POSITION
camPos = camMatrix.transform( nuke.math.Vector3(0,0,0) )
#UP VECTOR
upVect = camMatrix.yAxis()
#LOOK AT POSITION
lookAt = nuke.math.Vector3( camMatrix[8], camMatrix[9],
camMatrix[10] )
lookAt.negate()
lookAt += camVect
This seems to work like a charm. I do wonder if there is a more elegant way to
get the initial lookAt though without slicing?
Cheers,
frank
On Mar 8, 2011, at 12:45 PM, Frank Rueter wrote:
> hm, I'm having trouble getting the right lookAt vector.
> this is what I'm doing:
>
> def getWorldMatrix( node ):
> m = nuke.math.Matrix4()
> for i in range(0,16):
> m[i] = node['world_matrix'].value(i%4, i/4)
> return m
>
> camNode = nuke.createNode( 'Camera2' )
> camNode['translate'].setValue( (1,2,3) )
> camMatrix = getWorldMatrix( camNode )
> worldLookAt = nuke.math.Vector3(0,0,-1)
> localLookAt = camMatrix.vtransform( worldLookAt )
> localLookAt = camMatrix.vtransform( worldLookAt )
> print localLookAt
>
>
>
>
>
> The result for the lookAt vector stays at { 0,0,-1} even though the camera's
> position is {1,2,3}.
> What am I missing?
>
> Cheers,
> frank
>
>
>
>
> On Mar 7, 2011, at 3:42 PM, Ivan Busquets wrote:
>
>> Hallo, Frank.
>> Despite writing that tutorial, I am by no means an expert in matrix and
>> maths. :)
>>
>> But I've learnt a thing or two about how they apply to things like camera
>> transforms, etc., so hopefully I'll be able to help with this one.
>>
>> I think the easiest in your case (easiest to code, not necessarily to
>> understand :p) is to start with the camera's transformation matrix instead
>> of the Euler rotations. If you want to use Euler angles as a starting point,
>> then you'll need to check for rotation order and such.
>>
>> To get the camera's transformation matrix, i usually do one on the following:
>>
>> - If your camera doesn't have any other Cameras or Axis driving its final
>> transformation, you can simply do:
>>
>> cam_transform = nuke.toNode('camera_name')['transform'].value()
>>
>> - If you're interested in getting the final transformation matrix of a
>> concatenated set of transforms, I usually use the following to wrap the
>> contents of the 'world_matrix' knob into a nuke.math.Matrix4 object:
>>
>> #########
>> def getCameraTransformMatrix(cameraNode):
>> m = nuke.math.Matrix4()
>> try:
>> for i in range(0,16):
>> m[i] = cameraNode['world_matrix'].value(i%4, i/4)
>> except:
>> print "couldn't get all values for a 4x4 Matrix. Identity matrix returned
>> instead"
>> m.makeIdentity()
>> return m
>> ##############
>>
>>
>> Finally, once you have your transformation matrix in a nuke.math.Matrix4
>> object, getting the lookAt and the Up vectors should be a matter of setting
>> the initial direction of those two vectors, and then transform them using
>> the matrix.
>>
>> I.E.
>>
>> # For a single, non concatenated camera. Otherwise use the helper funcion
>> above.
>> cam_matrix = nuke.toNode('camera_name')['transform'].value()
>>
>> # set up initial lookAt vector
>> lookAt = nuke.math.Vector3(0,0,-1) # because Nuke's default cam looks at -Z
>>
>> # Initial up vector
>> up = nuke.math.Vector3(0,1,0)
>>
>> #Final lookAt vector
>> lookAt = cam_matrix.vtransform(lookAt)
>>
>> #Final up vector
>> up = cam_matrix.vtransform(up)
>>
>> # Note that the key here is to use the "vtransform" method instead of
>> "transform", since you want to apply the transformation to a direction
>> vector, but ignore any scaling or translation.
>>
>> I think this should get you the right values to go from a Nuke camera to,
>> say, a Camera + Aim + Up in Maya (don't have Maya here to check, though).
>>
>> Hope that helps!
>>
>> Cheers,
>> Ivan
>>
>>
>> On Sun, Mar 6, 2011 at 3:06 PM, Frank Rueter <[email protected]> wrote:
>> Hola,
>>
>> has anybody converted a nuke camera (Euler rotations) to LookAt and Up
>> vectors? as used by some other applications
>> I am just starting to read Ivan's tutorial on Nukepedia hoping it will shed
>> some light on this for somebody with very limited understanding of 3D
>> rotational maths (aka "me") but thought I'd spread my feelers in here at the
>> same time.
>>
>> Cheers,
>> frank_______________________________________________
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