Transform point using localToSceneTransform

Jim Graham james.graham at
Tue Jul 24 16:06:23 PDT 2012

Hi Pedro,

delta transform is transform without translation.  It is primarily used 
to transform magnitudes that have no position so you only modify them 
with the scale, shear, and rotation aspects of the matrix (i.e. 
everything but the translate components).

For some reason I got the impression that Vector was only used to 
represent magnitude because people were bringing up delta transforms in 
the context of talking about it.  If it is a 1x4 vector then it is just 
Point3D+perspective-w-element, [x,y,z,w] no?  Point3D can participate in 
4x4 transforms, supplying an implicit w=1 component, though it can't 
store the resulting w component if the matrix doesn't have 0,0,0,1 for 
the last 4 elements (i.e. in perspective camera matrices)...


On 7/24/2012 3:55 PM, Pedro Duque Vieira wrote:
> Hi,
>> I've already commented on this in the matrix algebra thread, but I
>> wanted to throw into this discussion the following point:
>> I'm neutral on whether or not we need Vector - I'll leave that to the
>> people with extensive 3D experience to comment.  But, if transformation
>> of vectors makes better sense to do a delta transform, and if we are
>> adding deltaTransform() methods for other types (which I think we should
>> do), then I think the "transform" method that does a "delta transform"
>> on a Vector should actually be named "deltaTransform" for consistency,
>> even if it is obvious that a vector should only be transformed that way...
> I don't know what a delta transform is (never used it on my 3d work
> background), so I cannot comment on that part.
> All I can say is that I did use transform a vector by a given matrix
> transform and it makes sense. It's basically a multiplication of a 4x4
> matrix transform with a 1x4 matrix, just like what happens when you
> transform a point3d.
> So I think:
> - void transform(Vector3d)
> Should be present on the transform3d class.
> Just my 2 cents,

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