Boni opened this issue on Jun 30, 2014 · 61 posts
bagginsbill posted Fri, 11 July 2014 at 2:29 PM
The Reflect node gives us reflections from objects. (including the EnvSphere)
The Blinn node gives us reflections from Poser lights. Lights are a fiction - they're not really there. They have no size.
The Blinn eccentricity affects the apparent size of the light source as well as the apparent blurriness of the object. It has to be matched to the Reflect node's softness. But not literally matched - the two values have very different interpretations.
In my shader work, I express the "blur" of a surface with the word "blur". Blur can be 0, .1, .5, .75737, 1, 1.5, 2, 5, etc. Above 5, Poser's Reflect node softness really breaks down and doesn't work, so watch out for that.
To translate blur to Reflect and Blinn nodes, I use the following rules:
Reflect.softness = blur <--- that was easy!
Blinn.eccentricity = .03 + .065 * blur
In this shader, I used a blur of .1, and so that is how the values got there.
The Blinn node also has its own built-in sort-of Fresnel effect (SpecularRollOff), which I turn off (set to 1 = no falloff) because I intend to always modulate reflections with a Fresnel_Blend node.
The Blinn Reflectivity controls its brightness. This is a "relative" term. If you try to understand this Reflectivity deeply, you will probably fail and we'll have to have a very long conversation about this one parameter and how Poser's unitless light system is kind of a pain.
Short answer, is I use this formula
Blinn.Reflectivity = 90 * (.5 ** blur)
That's 1/2 raised to a number equal to my chosen blur. In this case, with blur = .1, that comes to 83.973. (I did not type this - VSS built it.)
The Reflect Quality parameter is very fussy to deal with. As a rule of thumb, for curved things it can be under .5 with moderate blur. If your blur is 0, it can be .1. VSS generates appropriate values based on the blur. For eyes which really don't need blur at all, you could speed them up by removing the blur (blur = 0) and set the Quality to .1.
I don't want to talk about RayBias. It's complicated. I left it at its default for now.
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)