"gltfviewer -s" results in no lighting

[JackKaiXing]

Describe the bug
in windows, command "gltf_viewer my.gltf", that point lighting effect is visible; however, command "gltf_viewer -s my.gltf",that point lighting effect is gone. However, we do not want to scale the scene.

Expected behavior
how could be modify the code to control this?

[JackKaiXing]

thanks in advance

[romainguy]

There’s a directional light by default, no point lights. Could you provide screenshots please? Directional lighting works with or without -s in all my tests.

[JackKaiXing]

without -s

with -s

and here is my gltf string, as listed below:
{
"asset": {
"version": "2.0",
},
"extensionsUsed": [
"KHR_lights_punctual",
"KHR_draco_mesh_compression"
],
"scene": 0,
"scenes": [
{
"nodes": [
0,
1,
2
]
}
],
"nodes": [
{
"mesh": 0,
"translation": [
-0.5439453,
0,
8.354431
],
"name": "Box001",
"rotation": [
0,
0,
0,
1
],
"scale": [
1,
1,
1
]
},
{
"translation": [
8.409393,
24.04018,
11.8579865
],
"rotation": [
-0.707106769,
0,
0,
0.707106769
],
"name": "PhotometricLight001",
"extensions": {
"KHR_lights_punctual": {
"light": 0
}
},
"scale": [
1,
1,
1
]
},
{
"translation": [
4.13425446,
-16.18853,
12.9804688
],
"rotation": [
-0.707106769,
0,
0,
0.707106769
],
"name": "PhotometricLight002",
"extensions": {
"KHR_lights_punctual": {
"light": 1
}
},
"scale": [
1,
1,
1
]
}
],
"meshes": [
{
"primitives": [
{
"attributes": {
"POSITION": 1,
"TANGENT": 2,
"NORMAL": 3,
"TEXCOORD_0": 4
},
"indices": 0,
"material": 0,
"mode": 4,
"extensions": {
"KHR_draco_mesh_compression": {
"bufferView": 0,
"attributes": {
"POSITION": 0,
"TANGENT": 1,
"NORMAL": 2,
"TEXCOORD_0": 3
}
}
}
}
],
"name": "Box001"
}
],
"accessors": [
{
"componentType": 5123,
"count": 36,
"type": "SCALAR",
"name": "accessorIndices"
},
{
"componentType": 5126,
"count": 24,
"max": [
58.259484098680986,
11.356984611626771,
62.89313910600879
],
"min": [
-58.2570391060088,
-0.061389106008793354,
-62.893139106008796
],
"type": "VEC3",
"name": "accessorPositions"
},
{
"componentType": 5126,
"count": 24,
"type": "VEC4",
"name": "accessorTangents"
},
{
"componentType": 5126,
"count": 24,
"type": "VEC3",
"name": "accessorNormals"
},
{
"componentType": 5126,
"count": 24,
"type": "VEC2",
"name": "accessorUVs"
}
],
"bufferViews": [
{
"buffer": 0,
"byteOffset": 0,
"byteLength": 573
}
],
"buffers": [
{
"name": "test",
"byteLength": 576,
"uri": "test.bin"
}
],
"materials": [
{
"pbrMetallicRoughness": {
"baseColorFactor": [
0.1764706,
0.388235331,
0.24313727,
1
],
"metallicFactor": 0,
"roughnessFactor": 1
},
"name": "01 - Default",
"emissiveFactor": [
0,
0,
0
],
"alphaMode": "OPAQUE",
"doubleSided": false
}
],
"extensions": {
"KHR_lights_punctual": {
"lights": [
{
"color": [
2.78720665,
0.5679655,
0.000001
],
"intensity": 10000,
"type": "point"
},
{
"color": [
0.904883146,
1.0083766,
1.19620013
],
"intensity": 10000,
"type": "point"
}
]
}
},
"extensionsRequired": [
"KHR_draco_mesh_compression"
]
}

[JackKaiXing]

In my gltf, there are two point light. we checked the code, without -s, gltf_viewer would execute function "fitIntoUnitCube", why is that?

[romainguy]

It does this so the loaded glTF can be visible from the default camera position and entirely visible on screen. This is a pretty common thing to do in 3D viewers.

[romainguy]

Can you please share the entire glTF file with us?

@prideout @bejado Any idea why scale would impact lights? I imagine we don't rescale their falloff which would explain why it's more visible without -s.

[bejado]

If the glTF file doesn't have a range set for punctual lights, we give it an arbitrary one (10.0 units I believe). When using -s, the light and geometry probably fall outside this arbitrary range. Perhaps we should be scaling this falloff, or at least using the surrounding AABB to dictate the falloff value.

[JackKaiXing]

The entire glTF file.

https://github.com/JackKaiXing/glTF/tree/master/glTF

[romainguy]

@bejado That must be it then, I don't see a range in the glTF file.

[JackKaiXing]

Based on the above discussion, we added "range":4000 for light property. with -s, lighting is still invisible.

[romainguy]

I can't open the glTF file in Blender because of the Draco mesh compression extension.

@JackKaiXing Sorry to bother you, do you have a version of the asset that doesn't use Draco? I'd like to check where the lights are.

[JackKaiXing]

@romainguy .

gltf with no draco compression: https://github.com/JackKaiXing/glTF/tree/master/glTF/gltf_WithoutDraco

[romainguy]

The positions are correct, so either there's a bug on our side or it's simply that the intensity of the lights isn't enough for the distances because of the falloff.

@JackKaiXing Could you try with brighter lights?

[JackKaiXing]

we tried brighter lights by changing its intensity and still no lighting .

[cx20]

It seems that this glTF model includes the KHR_lights_punctual extension, but I don't think Filament supports this extension yet.

For reference, here are the results displayed by other libraries.

Library	Result
Three.js
Babylon.js

Also, I think the lights on this model are too bright.

The specification of this extension says that the unit of intensity is candela (lm/sr).
https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual

[JackKaiXing]

sorry for the intensity of 50000 value, it is for our test. However, if we change the intensity to 3000, without -s there is lighting and with -s there is no lighting.

About KHR_lights_punctual, without -s, lighting effects is visible. so I do think it is related.

@cx20

[cx20]

@JackKaiXing I'm sorry. Your point seems to be correct, PhotometricLight001 seems to be a light included in glTF.

Sun light	Photometric Light 001	Image
off	on
off	off

[romainguy]

Filament supports KHR_lights_punctual.

[cx20]

Hmm, I tried to display the following model with gltf_viewer, but it doesn't seem to reflect the lights.

https://github.com/Reon90/glTF-Sample-Models/tree/master/2.0/Lights

No	object name	type	color	intensity
1	Light	point	[1,0,0]	5
2	Spot	spot	[0.1,0]	10
3	Spot.001	spot	[0,0,1]	10
4	Sun	directional	[0,1,1]	1

Sun	Spot.001	Spot	Light	Image
on	on	on	on

[romainguy]

Those intensities are too low for the default camera exposure. glTF uses photometric units, so those lights use 5 lumens, 1 lux, etc. Here is the scene with a different exposure:

[JackKaiXing]

Does exposure also works for my case? I really hope to find out as we do not scale the scene.

@romainguy

[romainguy]

Yes the exposure works since the light is visible without -s.

[cx20]

@romainguy Does exposure also work for the JavaScript API? I tried setExposure() in JavaScript API, but the box stayed black.

let aperture = 1;
let shutterSpeed = 1;
let ISO = 350;
this.camera.setExposure(aperture, shutterSpeed, ISO);

Perhaps I need to retrieve the glTF light extension information and set it individually like the embedded camera?

[romainguy]

Exposure should work in JavaScript yes. @prideout might help here

[prideout]

We do have a JavaScript binding for the 3-argument setExposure, but I have not tested it explicitly. I can give it a try. Let us know if you see any errors in your Developer Tools.

[prideout]

setExposure seems to work for me fine in JavaScript. Below are screenshots with ISO levels 50 and 200.

[cx20]

@prideout Hmm, I tried setting setExposure() in the gltf-test Filament sample, but it didn't work as expected.

https://cx20.github.io/gltf-test/examples/filament/index.html?category=tutorialModels&model=FlightHelmet&scale=3&type=glTF

setExposure()	Skybox	Lights	IBL	Image
N/A	On	Off	On
(1,1,100)	On	Off	On
(1,1,100)	On	On	Off

It would be helpful if you could give me some advice.

[romainguy]

Those results look correct to me. 1/1/100 is extremely bright, it's a 1 second exposure at ƒ/1, it's the kind of exposure you'd use for night time shots.

[cx20]

@romainguy I'm sorry, I don't know much about cameras, so please tell me what parameters I should set.

[romainguy]

For what? The exposure you want to set depends on the intensity of your lights and the visuals you want to achieve. Note that we have a tone mapper that helps with this called "display range". It shows the exposure in EVs using color codes.

[cx20]

@romainguy Thank you for the information. I have to go out now and will try it when I get back.

[cx20]

I completely misunderstood the use of shutter speed in setExposure(). As you pointed out, I used the reciprocal of the shutter speed, and that solved the problem of the blank white.

I improved the Filament sample in gltf-test so that you can adjust the Exposure settings like in gltf_viewer.
https://cx20.github.io/gltf-test/examples/filament/index.html?category=tutorialModels&model=FlightHelmet&scale=3&type=glTF

setExposure()	Image
(16,1/125,50)
(16,1/125,200)

I understand how to change the Exposure, but I couldn't figure out how to display the KHR_lights_punctual model in the JavaScript API. Can you give me some advice?

https://cx20.github.io/gltf-test/examples/filament/index.html?category=tutorialModels&model=Lights&scale=1&type=glTF

setExposure()	Image
(16,1/125,100)
(1,1,300)

[cx20]

I have confirmed that the JavaScript API can also display the lights of the KHR_lights_punctual extension by adding the following code.

const lights = asset.getLightEntities();
for (let i = 0; i < lights.length; i++) {
    this.scene.addEntity(lights[i]);
}

https://cx20.github.io/gltf-test/examples/filament/index.html?category=tutorialModels&model=Lights&scale=1&type=glTF

setExposure()	Image
(1,1,300)

https://cx20.github.io/gltf-test/examples/filament/index.html?url=https://rawcdn.githack.com/JackKaiXing/glTF/f593cb10952c373cc11074b50142ff3a299a89ea/glTF/gltf_WithoutDraco/test.gltf&scale=0.02

setExposure()	Image
(16,1/125,100)

[prideout]

I think this bug is resolved, if not feel free to add a comment.