RFR: 8234920: Add SpotLight to the selection of 3D light types [v21]

Tue Jun 8 21:21:18 UTC 2021

On Mon, 7 Jun 2021 23:38:44 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?
>> 
>> - [x] 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 and comparing this branch with `master` using a 1000 division sphere, 200 meshes, and 5000 meshes.
>> Using an AMD RX 470 4GB GPU.
>> 
>> In this branch, there is a possible CPU optimization for checking the light type and using precalculated values (in `D3DMeshView.cc` for d3d and `ES2PhongShader.java` for opengl). On the GPU, I tried 3 ways of computing the spotlight factor contributions (`computeSpotlightFactor`, `computeSpotlightFactor2` and `computeSpotlightFactor3`) trying out different branching and shortcuts.
>> 
>> ### Results
>> The CPU "optimizations" made no difference, which is understandable considering it will not be the bottleneck. We can remove these if we want to simplify, though maybe if we allow a large number of lights it could make a difference (I doubt it). I don't have a strong preference either way.
>> 
>> The sphere 1000 tests always gave max fps (120 on Win and 60 on Ubuntu).
>> 
>> **Win 10**
>> Compared with the `master` branch, this patch shows 5-10 fps drop in the mesh 200 test and ~5 in the mesh 5000 test. I repeated the tests on several occasions and got different results in terms of absolute numbers, but the relative performance difference remained more or less the same. Out of the 3 `computeSpotlightFactor` methods, `computeSpotlightFactor3`, which has no "optimizations", gives slightly better performance.
>> 
>> **Ubuntu 18**
>> The mesh 200 test always gave 60 fps because it is locked to this fps, so we can't measure the real GPU performance change.
>> The mesh 5000 test shows 2-6 fps drop from master, with `computeSpotlightFactor` > `computeSpotlightFactor2`  > `computeSpotlightFactor3` at in terms of performance (~2 fps difference each).
>> 
>> **Conclusion**: we can expect a 5 fps drop more or less with 3 point lights. `computeSpotlightFactor3` on d3d and `computeSpotlightFactor` on opengl gave the best performances.
>
> Nir Lisker has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Addressed doc review comments

I've finished reviewing the code for everything except the shaders themselves. That will be later this week I hope.

I left a few comments on the tests. I also have one suggestion for an additional system test. It would be useful to test that a `Spotlight` with values that simulate a `PointLight` -- `direction` of `(0, 0, 1)`, `falloff` of 0, `innerAngle` of 0, `outerAngle` of 180 -- produce the same results as a `PointLight`.

tests/system/src/test/java/test/javafx/scene/lighting3D/LightingTest.java line 59:

> 57: //  |/
> 58: //
> 59: public class LightingTest {

This class can be `abstract`.

tests/system/src/test/java/test/javafx/scene/lighting3D/LightingTest.java line 65:

> 63:     protected static final String FAIL_MESSAGE = "Wrong color value";
> 64: 
> 65:     protected static final int LIGTH_DIST = 60;

Typo: `LIGTH_DIST` --> `LIGHT_DIST `

tests/system/src/test/java/test/javafx/scene/lighting3D/PointLightAttenuationTest.java line 65:

> 63:         LightingTest.light = LIGHT;
> 64:         new Thread(() -> Application.launch(TestApp.class, (String[]) null)).start();
> 65:         assertTrue("Timeout waiting for FX runtime to start", startupLatch.await(5, TimeUnit.SECONDS));

We should be using at least a 10 second startup timeout. See [JDK-8198587](https://bugs.openjdk.java.net/browse/JDK-8198587).

tests/system/src/test/java/test/javafx/scene/lighting3D/PointLightAttenuationTest.java line 106:

> 104:             assertEquals(FAIL_MESSAGE, lambertSample * attn, sampledBlue, DELTA);
> 105: 
> 106: 

Unneeded extra blank line?

tests/system/src/test/java/test/javafx/scene/lighting3D/SpotLightAttenuationTest.java line 55:

> 53:     private static final int OUTSIDE_ANGLE_SAMPLE = 42;
> 54: 
> 55:     private static final double[] FALLOFF_FACTORS = new double[] {0.5, 1, 1};

Should that last value be `> 1` to test that case?

tests/system/src/test/java/test/javafx/scene/lighting3D/SpotLightAttenuationTest.java line 68:

> 66:         LightingTest.light = LIGHT;
> 67:         new Thread(() -> Application.launch(TestApp.class, (String[]) null)).start();
> 68:         assertTrue("Timeout waiting for FX runtime to start", startupLatch.await(5, TimeUnit.SECONDS));

10 seconds

-------------

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