[Gary Bidwell]

Reading the manual again, I came across these two lines:

'It is not recommended to have more than one Layer above the others set to Additive mode if its Layer weight is already 100%. This can make unnaturally bright materials which can introduce precision errors in the render (usually visible as bright spots)'

'Avoid having more than one layer set to a weight of 100 in Additive mode. A
material with three layers, two of which are set to Additive and have a weight of 100, will look unrealistically reflective. And it will also add to the render time. This does not apply to layers in Normal mode.'

So why does the car paint wizard completely ignore/contradict this?

I think we need a completely new car paint shader in Maxwell.

[eric nixon]

Yes, the wizard isnt so good, but it is using R2 which darkens thinngs, so in this case 100% could mean much less, I think that wizard can make some nicer darker coloured carpaints, but its not a good mxm structure for universal CP...

My philosophy with additives is only use when you have to / or when its v. convenient, maybe for a darker material, additives with transparency generally sucks, but with thin-sss can be ok.

It all depends but 98% of the time never needed

[tom]

Additives are really not suggested except very special cases. Carpaint is one of them and I admit the current wizard is only good with dark base colors. When you use normal blending, the weight values are reducing the effect of corresponding BSDF. It's safe yet not desired because, let's say you need a specular coat which requires a fresnel reflectivity of Nd 1.8 and you don't want to weaken it with the weight. Normal blending cannot be an option here unless you use Coatings but you're only limited to one coating per BSDF and unlike additives it's not possible to make them rough when needed.