The performance cost of decals?

[DELGOODIE]

Title, how expensive are decals in relation to just a texture sample or other options?

I am mainly debating two art styles:

1. use only few world aligned master materials on my entire map, but tons of decals
2. bake all decals and materials into textures and have roughly 1 mat per object but no decals

A third option could be creating a second UV channel which allows me to basically just “place” the texture as a decal only in one spot on the mesh.

I really would like to do the first option as it is fastest, so i would sacrifice a bit of performance, but not say, a 25% framerate reduction.

[ZacD]

Decals aren’t that expensive, cheaper than having a bunch of unique textures and materials everywhere.

[DELGOODIE]

okay, glad to know decals aren’t bad.
Do you think it would be cheaper though to have:

~10 master materials that use triplanar or other global shading methods and have more shader instructions ~200-300 but 0 - 2 texture samples

~1000 materials (many will be material instances though!) with 2-3 texture samples (for pbr channels) but minimal shader instructions (pretty much just the texture sample)

[ZacD]

Material instances are each an additional draw call, material instancing doesn’t improve performance, it’s only there for organization and workflow reasons.

[DELGOODIE]

oh hmm i thought i was getting some perf benefits from material instances.

so it sounds like i should stick to the 10 master map route. would it be equal performance no matter how many material slots i use, as long as im using the same 10 mats. for example if i have 10 mats, 100 actors, each actor only uses 1 mat or each actor has 10 mat slots and uses every single mat

or would it be better to merge the entire level into one static mesh with 10 mat slots?