getShadowMask equivalent in TSL

[Samsy]

Description

Hey there !

Ocean Water from legacy to TSL,

The Ocean TSL examples does not support shadow-mapping as in the legacy one :

https://github.com/mrdoob/three.js/blob/master/examples/jsm/objects/Water.js#L181C71-L181C84

I was looking for an equivalent of getShadowMask, to be used inside a fragmentNode, checked on the examples and the wiki but had no chance :

float shadowMask = getShadowMask();

[sunag]

@Mugen87 I think these examples like Water should be moved to .colorNode instead of .fragmentNode and perhaps we could use a MeshLambertNodeMaterial for shadow materials, must be compatible with fog, and MRT and would be more in line with a "real" lighting proposal.

[Mugen87]

That sounds good to me. Using fragmentNode was a start but it's indeed better to keep as much as built-in material features as possible.

[Samsy]

About general customisation of materials, Is there a way to get access an equivalent of getShadowMask ?

[WestLangley]

Water.js was introduced back when the three.js Lambert shader was implemented via per-vertex lighting. Hence, the need for getShadowMask(), which is a hack.

The same hack is required by MeshGouraudMaterial, where shadows not only have the incorrect tint, they are highly-sensitive to the tessellation of the geometry.

I am inclined to think that a better approach would be to improve the water shader -- and, perhaps, deprecate both MeshGouraudMaterial and getShadowMask().

[Mugen87]

In the meanwhile, I also think that just having Phong shading in materials is more beneficial than the small performance benefit of Gouraud shading. We end up with more consistent materials and less edge cases.

Hence, I support the suggested deprecation.

[sunag]

About general customisation of materials, Is there a way to get access an equivalent of getShadowMask ?

Since shadow is the absence of light, in this case when we update Water to a material that is compatible with lighting, you can use material.receivedShadowNode to manipulate the shadow #29840