# How to get linear data from R, G, B & Alpha channels of a file?
**URL:** https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425
**Category:** Questions
**Tags:** materials, textures, shaders
**Created:** [June 22, 2021, 9:46am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425 "2021-06-22T09:46:01Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 22, 2021, 9:46am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/1 "2021-06-22T09:46:01Z")
Hi!
As long as we usually create Roughness, Metallic and some other channels as grayscale images with float/Linear profiles then I have the next question: is it possible to read different color channels separately from a file and use them as texture maps?
For exmaple, in Unreal Engine they do it like this: **Red (1)** channel is used for the Ambient Occlusion map, **Green (2)** — for the Roughness and **Blue (3)** — for the Metallic:
Thank you in advance!
---
### Author:  [@prisoner849](https://discourse.threejs.org/u/prisoner849)
#### Post date: [June 22, 2021, 10:00am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/2 "2021-06-22T10:00:49Z")
Hi!
You can see in the docs of `MeshStandardMaterial` that `aoMap` reads red channel, `roughnessMap` reads green channel, `metalnessMap` reads blue channel of a texture. So you can write them in one texture.
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 22, 2021, 10:09am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/3 "2021-06-22T10:09:42Z")
Does this mean that I don’t have to do anything special for this to work and this is done by default?
---
### Author:  [@prisoner849](https://discourse.threejs.org/u/prisoner849)
#### Post date: [June 22, 2021, 10:16am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/4 "2021-06-22T10:16:31Z")
Reading the docs on `MeshStandardMaterial`, pay attention to this sentence in the `aoMap` section`: _The aoMap requires a second set of UVs._
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 22, 2021, 10:40am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/5 "2021-06-22T10:40:57Z")
And what does it mean in the context of Three.JS and gltf? I know how to make several UVs for one mesh in 3D editor. Is it what should be done?
---
### Author:  [@prisoner849](https://discourse.threejs.org/u/prisoner849)
#### Post date: [June 22, 2021, 10:48am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/6 "2021-06-22T10:48:01Z")
Maybe this topic will be helpful: [Help with aoMap of GLTF/GLB model - #3 by donmccurdy](https://discourse.threejs.org/t/help-with-aomap-of-gltf-glb-model/14265/3)
PS Feel free to use “Search” on the forum 🙂
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 22, 2021, 11:05am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/7 "2021-06-22T11:05:54Z")
Thanks, @prisoner849 this helped with understanding.
Unfortunatelly, all this is not so obvious when I read those short descriptions in the docs. Even for me who is familiar both with 3D graphics and JS.
---
### Author:  [@donmccurdy](https://discourse.threejs.org/u/donmccurdy)
#### Post date: [June 22, 2021, 7:03pm UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/8 "2021-06-22T19:03:52Z")
GLTFLoader will automatically create a second set of UVs (by copying the first) if the model has an AO map and needs it.
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 23, 2021, 12:11pm UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/9 "2021-06-23T12:11:37Z")
> [@prisoner849](#):
>
> You can see in the docs of `MeshStandardMaterial` that `aoMap` reads red channel, `roughnessMap` reads green channel, `metalnessMap` reads blue channel of a texture. So you can write them in one texture.
Couldn’t find any examples of extracting data from the channels. I thought that if **aoMap** , **roughnessMap** and **metalnessMap** read color channels automatically, then something like this will work:
```javascript
const carMaterial = new THREE.MeshStandardMaterial({
map: textureLoader.load(`'car_color.png`),
roughnessMap: textureLoader.load(`car_AO-RG-ML.png`),
metalnessMap: textureLoader.load(`car_AO-RG-ML.png`),
aoMap: textureLoader.load(`car_AO-RG-ML.png`),
envMap: hdriTexture
});
carMaterial.side = THREE.DoubleSide;
carMaterial.metalness = 1;
carMaterial.map.encoding = THREE.sRGBEncoding;
```
…but it doesn’t work — the mesh is black.
In the example above in the **car\_AO-RG-ML.png** file I have R, G & B channels containing information about AO, roughness & metalness respectively (exported from Substance Painter).
Could you please, show a code example of how you do this properly?
---
### Author:  [@prisoner849](https://discourse.threejs.org/u/prisoner849)
#### Post date: [June 23, 2021, 12:19pm UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/10 "2021-06-23T12:19:38Z")
> [@Aleksei](#):
>
> 'car\_color.png
Is it a typo with `'` in the beginning of the file name?
Could you provide an editable working live code example, that demonstrates the issue?
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 23, 2021, 1:27pm UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/11 "2021-06-23T13:27:07Z")
Yeah, that was a typo. It isn’t in the actual code.
The live code example will take some time — will post in a while.
---
### Author:  [@Aleksei](https://discourse.threejs.org/u/Aleksei)
#### Post date: [June 24, 2021, 11:50am UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/12 "2021-06-24T11:50:07Z")
Here is the repository: [nordskill/cartest (github.com)](https://github.com/nordskill/cartest)
While working on it I noticed that the textures render as expected if set without the AO map. And with AO the model is black:
```javascript
matCar = new THREE.MeshStandardMaterial({
map: textureLoader.load(color),
envMap: obj.hdri,
roughnessMap: textureLoader.load(roughness),
aoMap: textureLoader.load(ao), // this line creates an issue
metalnessMap: textureLoader.load(metalness)
});
```
P.S. In the repository the textures are loaded in `loadCar()` function.
---
### Author:  [@prisoner849](https://discourse.threejs.org/u/prisoner849)
#### Post date: [June 25, 2021, 6:49pm UTC](https://discourse.threejs.org/t/how-to-get-linear-data-from-r-g-b-alpha-channels-of-a-file/27425/13 "2021-06-25T18:49:53Z")
You can load that texture once and use it in three parameters of material.
Also, I used two directional lights in the scene. [https://jsfiddle.net/prisoner849/81Lr0jyx/](https://jsfiddle.net/prisoner849/81Lr0jyx/)