RFR: 8234920: Add SpotLight to the selection of 3D light types [v6]

[Kevin Rushforth]

On Tue, 29 Dec 2020 12:03:14 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Added a SpotLight only to the D3D pipeline currently.
>> 
>> ### API discussion points
>> 
>> - [X]  Added `SpotLight` as a subclass of `LightBase`. However, it could also be a subclass of `PointLight` as it's a point light with direction and extra factors. I saw that `scenario.effect.light.SpotLight` extends its respective `PointLight`, but it's not a perfect analogy. In the end, I think it's a questions of whether `PointLight` will be expanded in a way which doesn't not suit `SpotLight`, and I tend to think that the answer is no.
>> 
>> - [X] The inner and outer angles are the "diameter angles" as shown [here](https://docs.microsoft.com/en-us/windows/win32/direct3d9/light-typeshttps://docs.microsoft.com/en-us/windows/win32/direct3d9/light-types).  I, personally, find it more intuitive that these are the "radius angles", so half these angles, as used in the spotlight factor formula. Do you think I can change this or do you prefer the current definition of the angles?
>> 
>> - [ ] The current implementation uses an ad-hoc direction property (using a `Point3D`). It crossed my mind that we could use the rotation transforms of the node to control the direction instead, just like we use the translation/layout of the node to get the position (there is an internal Affine3D transform for lights, not sure why `AmbientLight` needs it). Wouldn't that make more sense? When I rotate the light I would expect to see a change in direction.
>> 
>> ### Implementation discussion points
>> 
>> - [ ] I've gotten advice from a graphics engineer to treat point lights as spot lights with a 360 degrees coverage, which simplifies a few places. We can still try to optimize for a point light by looking at the light parameters: `falloff = 0` and `outerAngle = 180`. These possible optimization exist in `ES2PhongShader.java` and `D3DMeshView.cc`, and in the pixel/fragment shaders in the form of 3 different ways to compute the spotlight factor (the `computeLightN` methods). We need to check which of these give the best results.
>> 
>> ### Performance
>> 
>> Testing 3 point lights in order to compare with the [pre-patch performance](https://github.com/openjdk/jfx/pull/43#issuecomment-600632114):
>> 
>> Without the `falloff != 0` branching:
>> sphere 1000 subdivisions: 120
>> mesh 5000: 9.5
>> mesh 200: 111.5
>> 
>> With the `falloff != 0` branching:
>> sphere 1000 subdivisions: 120
>> mesh 5000: 9.3
>> mesh 200: 112.5
>> 
>> Ubuntu 20:
>> With the patch:
>> Mesh 200: 60 fps
>> Mesh 5000: 15 fps
>> Sphere 1000: 60 fps
>> 
>> Without the patch (master branch)
>> Mesh 200: 60 fps
>> Mesh 5000: 16.3 fps
>> Sphere 1000: 60 fps
>> 
>> So no major changes. I will repeat these tests to make sure there was no mistake.
>
> Nir Lisker has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update for the manual test utility

modules/javafx.graphics/src/main/java/javafx/scene/SpotLight.java line 192:

> 190:     private DoubleProperty falloff;
> 191: 
> 192:     public final void setFalloff(double value) {

I would also add the same language about the "valid range" being `falloff >= 0`.

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