Three.js: [WebGL2] NPOT Texture should not fallback in webgl2

[shawn0326]

Description of the problem

These fallback logic should be skipped in webgl2:
````javascript

// webgl2 skip this
_gl.texParameteri( textureType, _gl.TEXTURE_WRAP_S, _gl.CLAMP_TO_EDGE );
_gl.texParameteri( textureType, _gl.TEXTURE_WRAP_T, _gl.CLAMP_TO_EDGE );
_gl.texParameteri( textureType, _gl.TEXTURE_MAG_FILTER, filterFallback( texture.magFilter ) );
_gl.texParameteri( textureType, _gl.TEXTURE_MIN_FILTER, filterFallback( texture.minFilter ) );

// isPowerOfTwo should be (isPowerOfTwo || webgl2)
function textureNeedsGenerateMipmaps( texture, isPowerOfTwo ) {
return texture.generateMipmaps && isPowerOfTwo &&
texture.minFilter !== NearestFilter && texture.minFilter !== LinearFilter;
}
````

Three.js version

• [x] Dev
• [ ] r100
• [ ] ...

Browser

• [x] All of them
• [ ] Chrome
• [ ] Firefox
• [ ] Internet Explorer

OS

• [x] All of them
• [ ] Windows
• [ ] macOS
• [ ] Linux
• [ ] Android
• [ ] iOS

[mrdoob]

Sounds good to me.

@Mugen87 Does this conflict with #15286?

[Mugen87]

Yes. I'm not sure so far what parts of WebGLTextures needs to be modified to implement this feature request but it's probably better to do this after #15286 is merged.

[takahirox]

Ah, I missed when I made WebGL2 PR. Yeah we should fix. Perhaps replacing isPowerOfTwo in these two lines with ( isPowerOfTwo || capability.isWebGL2 ) may be easy to fix?

https://github.com/mrdoob/three.js/blob/dev/src/renderers/webgl/WebGLTextures.js#L88
https://github.com/mrdoob/three.js/blob/dev/src/renderers/webgl/WebGLTextures.js#L454

[Mugen87]

Yes, since textureNeedsPowerOfTwo() already returns false with a WebGL 2 rendering context. So textureNeedsGenerateMipmaps() needs a fix as well as setTextureParameters(). But I think the following two lines also need an enhancement:

https://github.com/mrdoob/three.js/blob/dev/src/renderers/webgl/WebGLTextures.js#L613
https://github.com/mrdoob/three.js/blob/dev/src/renderers/webgl/WebGLTextures.js#L673

[takahirox]

OK, I'll make PR to fix.

[takahirox]

I have difficulty naming variables in English. How var name var varname = ( isPowerOfTwo || capabilities.isWebGL2 ); should be? isValidSize?

[Mugen87]

Maybe needsPowerOfTwo? It's already used in the file but maybe not in your relevant scope.

[WestLangley]

How about this?

var supportsMips = ( isPowerOfTwo || capabilities.isWebGL2 );

[takahirox]

Thanks for naming. I made PR #15574