Added RGBMLoader. #21145

Mugen87 · 2021-01-25T19:08:22Z

Related issue: Fixed #20786

Description

Added RGBMLoader so RGBM encoded textures also work on iOS. The loader achieves this by parsing PNG files based on UPNG.js.

WestLangley · 2021-01-25T19:48:24Z

As in RGBELoader, I think there should be an onLoadCallback() where the following are explicitly set to appropriate values for the RGBM loader. Just for clarity.

texture.encoding
texture.minFilter
texture.magFilter
texture.generateMipmaps
texture.flipY

I am not sure if PMREM handles RGBM correctly or not...

WestLangley · 2021-01-25T19:49:44Z

~~webgl_loader_texture_rgbm.html is rendering upside down in this PR.~~

Mugen87 · 2021-01-25T19:51:03Z

webgl_loader_texture_rgbm.html is rendering upside down in this PR.

Have you rebuild three.module.js? Without it, it won't work.

Mugen87 · 2021-01-25T19:55:37Z

As in RGBELoader, I think there should be an onLoadCallback() where the following are explicitly set to appropriate values for the RGBM loader. Just for clarity.

I wanted to avoid the additional code since DataTextureLoader.parse() already configures the texture properties correctly. Besides, I personally prefer to only set values which differ from the default value. I've realized in the past that this approach is easier to read and understand.

WestLangley · 2021-01-25T20:09:29Z

I disagree 100%. Appropriate values must be set by the loader so the user does not have to worry about it.

Please advise:

Should RGBM textures have generateMipmaps set?
What should be the min/max filtering?
Why does the RGBM loader set the encoding to linear when linear is clearly incorrect?

Mugen87 · 2021-01-25T20:11:20Z

Why does the RGBM loader set the encoding to linear when linear is clearly incorrect?

Why was linear filtering configured in the existing code?

mrdoob · 2021-01-25T20:12:46Z

examples/webgl_loader_texture_rgbm.html

@@ -44,14 +46,10 @@

 				camera = new THREE.OrthographicCamera( - aspect, aspect, 1, - 1, 0, 1 );

-				new THREE.TextureLoader().load( 'textures/memorial.png', function ( texture ) {
+				new RGBMLoader().load( 'textures/memorial.png', function ( texture ) {

 					texture.encoding = THREE.RGBM16Encoding;


Shouldn't RGBMLoader set this encoding by default?

There is also RGBM7Encoding. I don't think it's possible to detect which encoding is used in a given texture so I thought it's better to set it in the example code.

Hmm, do we need RGBM7Encoding? 😅

Considering this was not working on iOS, I suspect this doesn't have't that much real usage...

@vjevremovic do we need both RGBM7 and RGBM16? Or can we just pick one?

export const RGBEEncoding = 3002; export const LogLuvEncoding = 3003; export const RGBM7Encoding = 3004; export const RGBM16Encoding = 3005; export const RGBDEncoding = 3006;

I'm not sure we need that many encodings...

/cc @bhouston

I'd default the encoding to RGBM7Encoding. At least it will render correctly up to an exposure factor. Defaulting the encoding to Linear is just wrong.

Although technically not correct, I've read that the resulting artifacts due to linear filtering with RGBM or RGBD can be considered as acceptable. This explains why you see the usage of linear filtering with both approaches.

But I understand that it depends on the texture data and the personal preference what kind of filtering is appropriate.

@elalish @MiiBond What is your recommendation? Should we keep the usage of linear filtering? Or default to nearest?

@Mugen87 I, too, think Linear filtering is acceptable, even if not correct. I am not sure about mip generation, though. I guess defaulting to false is OK.

So how do users other than @bhouston create RGBM files? Do they use a Blender add-on or something?

I would like to know that too...

Three.js has the ability to take a RGBE/HDR texture and encode it in RGBM just rendering from one texture to another using an encoding.

To make it easier one could make a Three.js example that could transcode between all these image formats pretty quickly. webgl_texture_encodings.html maybe? I seem to remember this suggested like 4 years ago.

I've hacked something together to test the RGBE to RGBM conversion for webgl_texture_encodings. The following fiddle loads a RGBE texture, converts it to RGBM and outputs the PNG on the website.

https://jsfiddle.net/94d5ymwj/

However, I've encountered an issue. It seems the encoding of the resulting RGBM texture is not correct. If I use the result in the RBGM example, it looks wrong, see https://jsfiddle.net/jg2so8mn/

I wonder what bit is missing 🤔 . Maybe a precision related issue?

Never mind! I've resolved the issue my manually encoding the PNG via UPNG.js and not using canvas. Updated fiddle:

https://jsfiddle.net/2do9arLf/1/

Not sure but it seems when applying the image data to the canvas, a color space conversion was applied on the texels.

vjevremovic · 2021-01-25T21:22:32Z

@mrdoob Yes. We need both, as it determines precision people can use. We use RGBM7 as we have more need for darker areas to have enough data points, but RGBM16 is legitimate, too. I would suggest we keep both as they already exist.

mrdoob · 2021-01-26T11:04:18Z

@vjevremovic Okay. What about LogLuv?

mrdoob · 2021-01-26T16:39:57Z

Thanks!

MiiBond · 2021-01-26T17:49:29Z

@elalish @MiiBond What is your recommendation? Should we keep the usage of linear filtering? Or default to nearest?

Yeah, linear usually looks okay for RGBD and RGBM. But not RGBE or LogLuv.

mrdoob reviewed Jan 25, 2021

View reviewed changes

mrdoob added this to the r125 milestone Jan 25, 2021

Added RGBMLoader.

5eba37e

Mugen87 force-pushed the dev2 branch from 8ef494a to 5eba37e Compare January 26, 2021 09:21

mrdoob merged commit 16eb3ec into mrdoob:dev Jan 26, 2021

Mugen87 mentioned this pull request Jan 29, 2021

Examples: Regenerate RGBM textures. #21173

Merged

Maksims mentioned this pull request Mar 5, 2021

Weird texture .exr .hdr artifacts on IOS device playcanvas/engine#1930

Closed

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Added RGBMLoader. #21145

Added RGBMLoader. #21145

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Added RGBMLoader. #21145

Added RGBMLoader. #21145

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