RFR: 8234920: Add SpotLight to the selection of 3D light types [v9]

[Nir Lisker]

On Thu, 25 Mar 2021 02:02:25 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>>> I the rotation needs to apply to whatever the direction vector is: whether that's implicitly (0,0,1) if we don't provide a separate direction vector or whether it's the user provided direction vector, it would be odd to ignore transforms if you set the vector.
>> 
>> I see, so we compose the transforms on top of the direction vector. It's an option indeed.
>> 
>>> If we don't provide a vector, we could always add it later if people ask for it, so maybe it is better to leave it off if we aren't sure.
>>> 
>>> The question then becomes how easy is it to modify the direction vector using the node transforms?
>> 
>> Yes, the ease of use is the issue I brought up initially with this approach. The rotation transforms are non-commutable, so it's going to be unintuitive for complex operations. A look-at method could be very useful not only in this case, but for any node in a 3D scene (or even 2D). Do you think that this is a worthy addition?
>
> I think I corrected the GL pipeline issue. The dot product should have used the negative light direction. It worked for me because I was testing in the -1 z direction instead of the +1. I still don't know why Mac and Linux would have given different results. This is what I get after the commit:
> 
> ![Screenshot from 2021-03-25 03-59-57](https://user-images.githubusercontent.com/37422899/112407458-c941cc80-8d1e-11eb-85c2-468508e5018a.png)

If you want to test aiming the light with transforms instead of a direction vector, I modified the `NGSpotLight` and `AttenLightingSample` files to use the rotation transforms.

[transforms.zip](https://github.com/openjdk/jfx/files/6212221/transforms.zip)

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PR: https://git.openjdk.java.net/jfx/pull/334