is that normal that the principled makes the hair more noisy? specially at the backside of the hair.
Principled as compared to which other? I guess that depending on the components of the node, if it has glossiness or other component more difficult to calculate, then yes, you're going to get more noise. Some rays need more samples to clear than others and as you make a material more complex and introduce more properties you're going to get noisier renders that need more samples.
Yes i meant by the 2 : the double hair BSDF mix ( left image ) and the simple Principled Hair BSDF (right image)
Thanks for the answers Omar, Martin . Indeed i was again bumped into a beginner issue where i didnt even understand that a simple image can be sample sized . so far never rendered anything so i didnt know that 128 sample is way to low for such a thing so i bumped it up 2000 and now looks correct even the principled one.
yes i see the Chiang option as default here . i dont touch it since the video doesnt have it . when i become enough good to make hairs and stuff. ill read more about those variation too . now not neccecary i think.
