Found out that the hair density parameter dial puts 1 hair
in a hair group area (the polygons that make up the group) for every 1.36 units. No matter what the size of the polygons
etc. I took the one sided square prop from the props section in the poser library and grew hair on it.

Also found out that zeroing out all the parameter dials
and setting the hair length parameter dial to .9 that the
length of hair is aprox equal to 1 foot. There is some
varation in the hair tho there should not be with the
length variance parameter dial set to zero. It varies
the length of random hairs so the hair looks more natural.

At zero it should not have any effect at all. With the following info we now have a better idea into placing hair on the head, body, etc. As to amount of hair in a area and length of hair. Brad.

Message edited on: 05/14/2005 14:51

Message edited on: 05/14/2005 14:52

I'm trying also to understand the mysteries of the hair engine.

I understand the "Hair Density" dial (as the name says) control the hair density that is measured in hairs per area unit. For example:

The "One sided square" measures 0.1 x 0.1 Poser Native Units (let me call it as pnu). That prop has only 1 poly.
Creating hair on this entire prop and setting the hair density to 10000 hairs/square pnu will generate:
0.1 x 0.1 x 10000 = 100 hairs.

The "Square Hi-Res" measures 0.7 x 0.7 pnu. That prop has many polys. Creating hair on this entire prop and setting the hair density to 10000 hairs/square pnu will generate:
0.7 x 0.7 x 10000 = 4900 hairs.

Any way, interested in any further explanations about this subject.

Thanks

A simple hair room tutorial, mostly for styling.
The furred MilCat is model in this tut.

You find it here.

Findings:

The "Hair Density" dial controls de density of the group and shows the number of Hairs in the faces (poly). It does not show the total number of hairs, but only the number of hair in the faces.

Hairs = Vertices + Hairs in Faces

Hairs = total number of hairs in group
Vertices = total number of vertices in group (1 hair in each vertice)
Hairs in Faces = total number of hairs in all faces of that group

Hairs in all faces = SUM(INTEGER(density X face area))
Hairs in Dial = INTEGER(density X total area)

obs:
4-side poly (QUAD) = 2 faces
3-side poly (TRIA) = 1 face

Minimun number of hairs in face = 1

Lets test with the BALL prop:

Area: 0.030684 poser native units (got from 3DS)

162 vertices
280 QUAD ( 1 QUAD = 2 faces )
40 TRIA ( 1 TRIA = 1 face )

The minimum number of hairs is:

7 x 20 QUAD x 2 hairs/poly = 280 hairs
2 x 20 TRIA x 1 hair/poly = 40 hairs
TOTAL = 320 hairs in face (plus 162 vertice-hairs).

The first chance in the number of hairs should be an increase in the middle layer of the ball, from 2 hairs to 3 hairs.

1 x 20 QUAD x 3 hairs/poly = 60 hairs
6 x 20 QUAD x 2 hairs/poly = 240 hairs
2 x 20 TRIA x 1 hair/poly = 40 hairs
TOTAL = 340 hairs in faces (plus 162 vertice-hairs).

Density = 340 / 0.030684 = 11081

So, any density below 11081 (including density = 0) will generate the same result:
320 face-hairs (plus 162 vertice-hairs), or in other words, any density above 11081 should create more hairs than the minimum.

But for some reason, Poser Hair engine will only start to create more hairs, with density above 11244, informing the generation of 344 face-hairs, but in reality, that will generate 400 face-hairs (plus 162 vertice-hairs).

1 x 20 QUAD x 4 hairs/poly = 80 hairs
2 x 20 QUAD x 3 hairs/poly = 120 hairs
4 x 20 QUAD x 2 hairs/poly = 160 hairs
2 x 20 TRIA x 1 hair/poly = 40 hairs
TOTAL = 400 hairs in face

Conclusion: My maths can get close, but can not get exact results. So, I can not explain exactly how it works.

ah ok i see i was a little off on the hair density. off with his head. lol