Data texture with LuminanceFormat used as alphaMap broken from r136

Describe the bug

After upgrading from v135 to latest the data texture I was using is now logging WebGL warnings to console, looking through the changelog there doesn’t seem to be any breaking changes I should be aware of outside of setting needsUpdate. The change that affected this was introduced in v136.

WebGL warning: texStorage(Multisample)?: internalformat: Invalid enum value LUMINANCE
WebGL warning: texSubImage: The specified TexImage has not yet been specified.

Code

import {
  DataTexture,
  LuminanceFormat,
  UnsignedByteType,
} from 'three';

const primaryMask = new Uint8Array(2500);

const texture = new DataTexture(
  primaryMask,
  50,
  50,
  LuminanceFormat,
  UnsignedByteType
);

texture.needsUpdate = true;

In v135 - nothing logged to console, alphaMap working as intended (partial transparent) In v136 - two warnings logged to console, alphaMap not working as intended (everything transparent)

Live example

• r135 WORKS https://codesandbox.io/s/wild-microservice-7yobcp?file=/src/index.js
• r139.1 DOES NOT WORK https://codesandbox.io/s/crazy-mcclintock-09k4pb?file=/src/index.js

Expected behavior

No warnings logged to console, transparency working as intended.

Platform:

• Device: Desktop
• OS: MacOS
• Browser: Firefox
• Three.js version: r136

[WestLangley]

@madou You can use this pattern to support a single-channel alpha map texture using RedFormat with three.js r139.

material.onBeforeCompile = function( shader ) {

	shader.fragmentShader = shader.fragmentShader.replace(

		`#include <alphamap_fragment>`,

		`#ifdef USE_ALPHAMAP
			diffuseColor.a *= texture2D( alphaMap, vUv ).r;   // read red channel, instead
		#endif`

	);

};

You could also use NodeMaterial, I assume.

[Mugen87]

with RGFormat obviously it needs double the size of the array now so each array item now would be red/green?

Please keep in mind that gl.LUMINANCE is problematic since at least one WebGL implementation (ANGLE) has to expand texture data to four channels to make luminance textures work with Direct 3D. This is not necessary when using RGFormat (or RedFormat).

I do get one warning however which is THREE.WebGLTextures: sRGB encoded textures have to use RGBAFormat and UnsignedByteType - is that a benign warning? Everything is working as expected even with this warning.

I suggest you ask this question at the forum or stackoverflow. If it turns out to be a problem of three.js, we can reopen this issue.