Exposure settings #8407

superdump · 2023-04-16T20:39:37Z

Objective

Add basic exposure settings for aperture in f-stops, shutter speed in seconds, and sensitivity in ISO units as per Google's Filament: https://google.github.io/filament/Filament.html#physicallybasedcamera
Fixes Directional lights are 4800x dimmer than point lights and spot lights #8369

Solution

Add basic exposure settings for aperture in f-stops, shutter speed in seconds, and sensitivity in ISO units as per Google's Filament: https://google.github.io/filament/Filament.html#physicallybasedcamera

Changelog

Added: ExposureSettings component that can be added to an entity with a Camera to configure PBR exposure settings

Migration Guide

The ExposureSettings component on an Camera entity will be used to configure exposure for PBR rendering. Previously only directional lights were using hard-coded exposure, but now all light has exposure applied. This will mean that all light sources other than directional lights will be significantly darker. Adjust the exposure settings and light intensities as necessary.

alice-i-cecile · 2023-04-16T20:55:56Z

Adding to the 0.11 milestone as this change will be badly breaking and should be shipped sooner rather than later.

fintelia · 2023-04-16T20:57:45Z

crates/bevy_render/src/camera/camera.rs

+            aperture_f_stops: 4.0,
+            shutter_speed_s: 1.0 / 250.0,
+            sensitivity_iso: 100.0,


I'd suggest ditching these individual settings and just passing the ev100 value directly. There's lots of sources online that provide tables of ev100 values, for instance this one from wikipedia

Also, might be worth providing constants with a couple defaults. For instance, EXPOSURE_DIRECT_SUNLIGHT, EXPOSURE_INDOOR_LIGHTING, EXPOSURE_MOONLIGHT, etc.

Agreed! You could also provide an Ev100::from_camera(aperture_f_stops, shutter_speed_s, etc...) function.

Yeah, unless we had other effects of these parameters they should really be collapsed down into one.

Good idea @JMS55 - I was thinking that it would be good to expose (HA!!!) the functionality to provide the parameters for those who it is more familiar. Was first thinking of an enum, but I agree the constructor approach could be nicer.

@alice-i-cecile hmm... now that you mention it... the filament docs did talk about how the different parameters affect depth of field (or focal depth - the aperture setting I think, I'm not familiar with cameras beyond physics stuff) and motion blur (shutter speed).

That's correct :) At the same time, I don't think we want those baked into our rendering engine by default: motion blur and focal depth are very specific effects that should be used artistically.

We're not simulating a real camera IMO, so we should just expose Ev100 and then provide independent control for things like motion blur and focal depth when we have them.

fintelia · 2023-04-16T22:31:39Z

Skyboxes ~~and environment lights~~ may need changes as well, though I haven't looked into them in much detail.

Edit: Environment lights seem to be handled correctly, but the output from skyboxes still needs to be scaled by view.exposure (and probably a user-controllable scale factor so LDR skyboxes can be brighter than 1 nit).

superdump · 2023-04-17T09:39:53Z

Skyboxes and environment lights may need changes as well, though I haven't looked into them in much detail

The filament docs said that they pre-expose IBL sources too, as an alternative to just applying exposure to accumulated light from all sources. They do the pre-exposure for the sake of being able to use f16. I may switch over to trying to do individual source pre-exposure for that reason but I wanted to get the whole thing working first.

@fintelia do you feel like trying out my branch to see if it matches your expectations? To me with the default values that Filament suggests, everything is very dark. I tried to find suggested values for cameras via random searches but they also seemed very dim. I feel I need to read through everything and probably compare to a reference scene + rendered in something else that is reliable.

fintelia · 2023-04-17T21:42:02Z

Just tried out the 3d lighting example from this branch. I removed the ambient and directional light, changed all the other lights to be white, and set the exposure settings to have an EV=6.0. The result looks fairly reasonable to me for a scene with 3x 100W non-halogen incandescent bulbs:

fintelia · 2023-04-17T21:57:49Z

examples/3d/lighting.rs

@@ -207,6 +207,7 @@ fn setup(
    // directional 'sun' light
    commands.spawn(DirectionalLightBundle {
        directional_light: DirectionalLight {
+            illuminance: 1000.0,


The sun has an illuminance of ~100,000 lux. Though, having that bright a directional light that bright is of course going to overpower all the other lights in the scene (even stuff in shadows will mostly be lit by bounce lighting and light from the sky)

fintelia · 2023-04-17T22:00:52Z

crates/bevy_pbr/src/render/pbr_functions.wgsl

@@ -254,7 +254,7 @@ fn pbr(

    // Total light
    output_color = vec4<f32>(
-        direct_light + indirect_light + emissive_light,
+        view.exposure * (direct_light + indirect_light + emissive_light),


This assumes that indirect light is already in photometric units. There may need to be a scale factor to undo any pre-exposure that's baked into the contents of the cubemaps.

Yeah. There was talk about an "intensity" field for environment map lighting. I decided to leave it out in my original PR because I was worried it would be abused. Maybe it's time for that now.

…_jms

JMS55 · 2023-08-22T04:53:50Z

@superdump rebased, converted ExposureSettings to hold EV100 directly, and did some misc work superdump#32.

Remaining TODO:

~~Add an exposure_correction/intensity/pre_exposure kinda field to EnvironmentMapLight~~
~~Add an exposure_correction/intensity/pre_exposure kinda field to Skybox~~
~~Apply exposure to Skybox output (can premultiply with the above field on the CPU)~~
Fix all the now broken looking examples (maybe change default point and spotlight intensities?)
~~Docs~~
Migration guide

fintelia · 2023-08-22T05:38:44Z

I'd suggest against changing the default intensities for point/spot lights. An 800 lumen (i.e., 60 W incandescent brightness) light is more likely to be what a user wants compared to a 3.6 million lumen one. It means that, say, a flashlight will be completely overpowered by the light of the sun, but that's true in the real world too!

Rather, the main suggested mitigation should be to specify exposure settings corresponding to an indoor or night scene. Then making sure the scale of the scene is accurate in meters. And only once those are both calibrated should you start increasing the number/brightness of lights.

crates/bevy_core_pipeline/src/skybox/mod.rs

superdump · 2023-09-01T17:06:57Z

I can’t approve my own PR. But, as it is my PR, it needs @robtfm ’s approval and we can merge it, or two community reviews.

JMS55 · 2023-09-03T20:47:12Z

We still need to fix all the examples...

Changelog/migration guide also needs to mention the other newly added stuff like PhysicalCameraParameters and skybox/envmaplight brightness controls.

GitGhillie · 2023-12-15T21:54:47Z

Just tried this PR with a scene exported from Blender (Eevee) containing one point light:

It's a bit dark but tons better than before. Do we want to adjust the default exposure to roughly match that of Blender (Eevee)?

Also, feel free to let me know if I can help with fixing the examples. In that case please let me know if 'calibrating the examples' means actual calibration or just try to match it by eye :)

JMS55 · 2023-12-15T22:22:04Z

@GitGhillie Fixing the examples would be a huge help :). It's really the main blocker of this PR. @fintelia suggested what we should do here: #8407 (comment). We should set an exposure that makes sense for the scene based on real-world values, and then tweak the light values to make sense. Also yeah, reevaluating the default exposure/light intensities probably makes sense.

This PR itself is out of date, but I've just rebased it. Please use this branch as a base for your changes: https://github.com/JMS55/bevy/tree/exposure_jms

fintelia · 2023-12-16T00:33:13Z

I did some investigation of Blender's handling of light intensity and I'm somewhat skeptical that their brightness levels are even meaningful...

Apparently, Blender uses a hard-coded conversion factor of 683 lumens/watt when exporting gltf (applied here). While the Blender documentation provides a table of common wattage values with conversion ratio varying from 227 lumens/watt to 556 lumens/watt.

The term for this conversion factor seems to be luminous efficacy. And from what I can find online, the 683 lumens/watt number seems to be a theoretical upper bound and values as low as 15 lumens/watt apply to some light sources.

Weirdly, I wasn't able to find any reference to how Blender determines how much of a light source's power is visible light. That feels like a rather relevant factor given that the whole reason there isn't only one luminous efficacy value is because different kinds of light have differently shaped spectrums

GitGhillie · 2023-12-16T14:54:48Z

If I change the default exposure from EV100_OVERCAST: f32 = 12.0 to EV100_INDOOR: f32 = 7.0 everything does start to line up roughly with what I see in Blender. If their brightness levels aren't meaningful to reason about I think it's a good enough approximation.

Having a default exposure of 7 instead of 12 also avoids having intensity/illuminance values in the 10000s in the examples.

Here are some comparisons with an exposure of 7, with the Blender exposure and other settings at the default:
Point light 10W (Blender default).

Directional light 1W/m^2 (also Blender default. I assume they use 1W/m^2 as a default because the default exposure is for indoor scenes, and 1000W/m^2 (strength of the sun according to the Blender docs) would blow out the scene).

@JMS55 thank you! If people agree with changing the default exposure I can start adjusting the examples

superdump · 2023-12-16T19:30:16Z

@GitGhillie sounds fine to me.

GitGhillie · 2023-12-27T16:06:29Z

Ran into an issue while adjusting the transmission example:
When I increase the brightness of the candle to compensate for the changes in this PR the transmission effect seems to kind of disappear.

Same thing happens if instead I increase the exposure in the already present ColorGrading component.

If I leave everything as it was and adjust the scene using the new ExposureSettings it works fine. Is this the expected behavior?

Working on this branch btw: JMS55#16

GitGhillie · 2023-12-27T16:08:25Z

Also wondering what the difference is between the ColorGrading exposure and the exposure in ExposureSettings. Aside from being able to set ISO, aperture and f-stop independently.

coreh · 2023-12-28T20:04:59Z

~~I have a hunch it might be the heuristic to prevent firefly artifacts when refracting very bright pixel values, it had some arbitrary constant values that might need tweaking.~~

~~We might even need to make it a function of the exposure value to make it look right across a wide range of exposures. I'll give this a look later today and try to figure it out.~~

Edit: It wasn't that, what was actually happening was that we were using an already exposure adjusted image (the background) as the input to another exposure adjustment.

JMS55 · 2023-12-28T20:10:55Z

After talking to @DGriffin91 on discord, it sounds like we should keep ColorGrading exposure. We might also want to change it to take the new ExposureSettings.

fintelia · 2023-12-29T00:59:35Z

The exposure from ColorGrading is an exposure value offset that is meant to be subtracted from the camera's exposure, so I don't think re-using Exposure settings makes sense for it

coreh · 2023-12-29T03:48:15Z

Fixed the underexposed transmission on GitGhillie#1

(It's now three staggered PRs from this one 😆 🚂🚋🚋🚋)

GitGhillie · 2024-01-04T14:51:13Z

Alright folks, all examples adjusted (I count 59 examples with lights). It's not perfect but maybe a good time to get some feedback. Here are some notes:

Most examples are going to be slightly brighter/darker. I did this in favor of round numbers and sometimes a better look (imo).
There are some big numbers in there. I know fintelia suggested adjusting the scale of the scene but in most cases it felt like adjusting the scale or exposure would add lines of code that would distract from the example.
I think I would also prefer big numbers for lights vs smaller than 0 numbers for scale.
Nonetheless, the lights/exposure seem to be kind of on the dark side still? Thus requiring intensity values up to a million sometimes. I don't really have a good reference for this. Maybe it's just the consequence of a more physically based unit.
I tried adjusting the scale of the spatial audio example but it seemed to lessen the spatial effect so for now I just increased the brightness.
Maybe it's good to think some more about adjusting the default intensity of the point light. Currently a lot of LOC are added because the default is not sufficient.
The atmospheric_fog example is broken, and I don't see a quick setting that can fix it.

Anyways, this exercise has taught me a lot about Bevy. Don't be afraid to give feedback that would mean I have to go through everything again, I can probably do it a lot quicker the second time around :)

coreh · 2024-01-05T00:20:44Z

The atmospheric_fog example is broken, and I don't see a quick setting that can fix it.

On it!

coreh · 2024-01-06T04:03:33Z

Fixed the atmospheric fog example: GitGhillie#2

alice-i-cecile · 2024-01-14T23:27:09Z

Adopted! 🎉 Please review #11347

alice-i-cecile · 2024-01-16T14:54:04Z

Merging the adopted PR now!

@GitGhillie

Rebased and finished version of #8407. Huge thanks to @GitGhillie for adjusting all the examples, and the many other people who helped write this PR (@superdump , @coreh , among others) :) Fixes #8369 --- ## Changelog - Added a `brightness` control to `Skybox`. - Added an `intensity` control to `EnvironmentMapLight`. - Added `ExposureSettings` and `PhysicalCameraParameters` for controlling exposure of 3D cameras. - Removed the baked-in `DirectionalLight` exposure Bevy previously hardcoded internally. ## Migration Guide - If using a `Skybox` or `EnvironmentMapLight`, use the new `brightness` and `intensity` controls to adjust their strength. - All 3D scene will now have different apparent brightnesses due to Bevy implementing proper exposure controls. You will have to adjust the intensity of your lights and/or your camera exposure via the new `ExposureSettings` component to compensate. --------- Co-authored-by: Robert Swain <[email protected]> Co-authored-by: GitGhillie <[email protected]> Co-authored-by: Marco Buono <[email protected]> Co-authored-by: vero <[email protected]> Co-authored-by: atlas dostal <[email protected]>

superdump added 2 commits April 16, 2023 22:33

Implement basic exposure settings

432c427

WIP: Test exposure settings in lighting example

8fa78a9

superdump marked this pull request as draft April 16, 2023 20:39

alice-i-cecile added C-Feature A new feature, making something new possible A-Rendering Drawing game state to the screen labels Apr 16, 2023

alice-i-cecile added this to the 0.11 milestone Apr 16, 2023

alice-i-cecile added the M-Needs-Migration-Guide A breaking change to Bevy's public API that needs to be noted in a migration guide label Apr 16, 2023

fintelia reviewed Apr 16, 2023

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benny-n mentioned this pull request Apr 16, 2023

Directional lights are 4800x dimmer than point lights and spot lights #8369

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alice-i-cecile mentioned this pull request Apr 16, 2023

Dim point and spot lights by the same factor as directional lights #8378

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fintelia reviewed Apr 17, 2023

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fintelia mentioned this pull request Jun 10, 2023

Implement basic AutoExposure plugin #8809

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3 tasks

JMS55 modified the milestones: 0.11, 0.12 Jun 11, 2023

JMS55 added 4 commits August 21, 2023 21:08

Merge commit 'af0323a55e9cbfe28262fd500fbe21f8cf4c8ee4' into exposure…

cbeed57

…_jms

Rebase fixes

0cfbfd7

Switch ExposureSettings to hold an EV100 value, improve example.

ef62d30

Misc

f5c4166

JMS55 added 6 commits August 22, 2023 19:16

Apply PR feedback

ce69ab2

Add brightness control to Skybox

e144815

Apply exposure to skybox

56bb844

Add EnvironmentMapLight::brightness

4dd2ede

Add misc todo

64bcfa8

Misc rename, example fixes

f9e0730

superdump commented Sep 1, 2023

View reviewed changes

crates/bevy_core_pipeline/src/skybox/mod.rs Show resolved Hide resolved

superdump marked this pull request as ready for review September 1, 2023 12:38

alice-i-cecile modified the milestones: 0.12, 0.13 Sep 29, 2023

JMS55 mentioned this pull request Nov 28, 2023

Implement minimal reflection probes. #10057

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GitGhillie mentioned this pull request Jan 4, 2024

Change default exposure, adjust a few examples JMS55/bevy#16

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JMS55 mentioned this pull request Jan 14, 2024

Exposure settings (adopted) #11347

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alice-i-cecile closed this Jan 16, 2024

GitGhillie mentioned this pull request Jan 17, 2024

Restore brightness in the remaining three examples after exposure PR #11389

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GitGhillie mentioned this pull request Jan 29, 2024

Change light defaults & fix light examples #11581

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GitGhillie mentioned this pull request Feb 13, 2024

default point lights seems wrong after exposure #11577

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Exposure settings #8407

Exposure settings #8407

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superdump commented Apr 16, 2023

Objective

Solution

Changelog

Migration Guide

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