LDrawLoader: Fix slanted normals

[gkjohnson]

Related issue: --

Description

Fixes skewed normals from redundant quad vertices when generating smooth normals that were particularly noticeable on the studs. Here's a gif of the before and after fix:

And screenshots:

BEFORE	AFTER

Also semi-related I notice that after 2f09982 the LDraw example page looks very washed out and the lego models don't look bright and vibrant the way I expect them to. Was this intentional? I'm not sure I feel an environment map is the best way to demonstrate the models.

cc @yomboprime

[yomboprime]

Also semi-related I notice that after 2f09982 the LDraw example page looks very washed out and the lego models don't look bright and vibrant the way I expect them to. Was this intentional? I'm not sure I feel an environment map is the best way to demonstrate the models.

Yes, I also see the colors are like pastel tones. Also it seems that all the edge (contour lines) materials, except the transparent ones, are all gray. I don't know if they are being affected by illumination or the environment map, which should not be the case.

[WestLangley]

You need tone mapping when using an HDR environment map, which RoomEnvironment aims to replicate.

[gkjohnson]

You need tone mapping when using an HDR environment map, which RoomEnvironment aims to replicate.

I don't think it's just tone mapping. The changes in 2f09982 set the output encoding to sRGBEncoding which means the loaded LDraw material colors are assumed to be Linear which isn't the case. And even so my impression is the models as loaded are designed to look like they're from a lego instruction booklet which are rendered fairly simply. Here's a quick survey of the look of the model with different settings. "1" is what's on dev right now:

	lighting	tone mapping	material color space	output encoding	screenshot
1	env map	none	srgb	srgb
2	env map	ACES	srgb	srgb
3	env map	ACES	linear	srgb
4	directional + ambient light	none	linear	srgb
5	directional + ambient light	none	srgb	linear

I think 3 (environment map, tone mapping, and linear color space shading) is the most "realistic" looking model but 4 (simple directional light lighting, linear color space shading) best approximates the look of a lego model instructions. Unfortunately 4 requires manually converting colors from srgb to linear after loading them so 5 is the simplest approach. I'm happy to help adjust the example to whichever version above is the most desirable in another PR.

[WestLangley]

I don't think it's just tone mapping.

I did not mean to imply it was. I was just point out a fact. :-)

[WestLangley]

Approach 5 looks good, but it is just not correct to implement lighting in sRGB colorspace. I assume we want to demonstrate best-practices in the examples. Approach 4 does that.

MeshStandardMaterial should be be used with an environment map -- even for plastics. The envMap does not have to be HDR.

A studio environment map may provide more uniform lighting. White light will avoid hue-shifts.

If I remember correctly, these models utilize many materials -- all with different values for environmentIntensity. That seems odd to me.

[mrdoob]

I don't think it's just tone mapping. The changes in 2f09982 set the output encoding to sRGBEncoding which means the loaded LDraw material colors are assumed to be Linear which isn't the case.

Shouldn't the loader produce linear colors? What if someone wanted to mix Lego models with GLTF models? 🤔

I think 3 (environment map, tone mapping, and linear color space shading) is the most "realistic" looking model but 4 (simple directional light lighting, linear color space shading) best approximates the look of a lego model instructions.

I think I'm going to try doing a brighter RoomEnvironment and call it LegoEnvironment 🤞

[mrdoob]

Thanks!