GridMaterial renders mainColor again since version 9.10.1

Bugs
1

Latest version 9.10.1 breaks the GridMaterial with the transparent mainColor hack.
Version 9.10.0 works as expected.

Expected behavior:
If the material opacity is less than 1.0 the mainColor is rendered transparent and only the grid is visible.

Broken behavior in version 9.10.1:
The mainColor is rendered using the actual opacity value and no alternative is provided to render the GridMaterial with a transparent mainColor.

Recommended Fix:
Instead of providing a hack using opacity, maybe it is possible to allow the mainColor to be a Color4 instead of a Color3, or maybe add another property mainColorOpacity.

Code example that no longer works with version 9.10.1:

this._material = new GridMaterial(name+'Material', scene);
this._material.alphaMode = Engine.ALPHA_COMBINE;
this._material.backFaceCulling = false;
this._material.gridRatio = 0.1;
this._material.lineColor = new Color3(0.0, 0.0, 0.0);
this._material.mainColor = new Color3(0.0, 0.0, 0.0);
this._material.majorUnitFrequency = 10;
this._material.minorUnitVisibility = 0.2; // thin lines width multiplier
this._material.opacity = 0.99; // previously caused mainColor fully transparent.
this._mesh.material = this._material;

2

want to do a PR? that seems like a good fix to me

3

I see the same problem with this latest version 9.10.1

4

This is the PG that was done : 7 days ago.
There has been a lot of change in the GridMaterial that introduced this bug

I made a reproduction on the playground :

See the difference by switching versions of Babylon. With 9.10.1, the grid no longer has transparency and the lower version is correct.

The current result :

v9.10.1
v9.10.1954×660 156 KB

The previous result :

v9.10.0
v9.10.0955×627 173 KB

However, this property seems to solve the problem, because we only use the lines :
gridMaterial.linesOnly = true;