Feature Request: Envmap Fresnel Considerations and Phong Only Mode

[Jofoyo]

Automatically apply $fresnelreflection for LightmappedGeneric and $envmapfresnel for VertexLitGeneric

$fresnelreflection Contrary to what the wiki says, this value works inversely, in all games that I've tried, not just Black Mesa. This version has no fresnel range consideration and seems to lerp between one minus $fresnelreflection and 1 at glancing angle.

$envmapfresnel This value works normally, and a value of 1 applies full fresnel.
Fresnel ranges are taken from $envmapfresnelminmaxexp if there is no bumpmap. Otherwise fresnel ranges are taken from $phongfresnelranges.

Using fresnel helps get rid of the "clearcoat" look that envmaps usually come with and is overall more photoreal.

Also please consider a phong only mode so that materials with high roughness low metalness don't waste memory and filesize with albedo alphas. Alternatively consider sampling images min and max envmap intensity and discarding automatically if there's not enough contrast to warrant the envmap.

[koerismo]

Fresnel and a model phong-only mode have been implemented in v2.0.6-beta. I think that the sampling idea sounds great, but I do not want to dictate that automatically, since texture artists tend to look for extremely fine-grain detail and may just assume that the program is not functioning as intended when it is replaced by a single value.

Maybe having it as an option would be nice, but that's going pretty far considering that most people use this program to port realistic materials which have lots of noise and minor detail.