GMH2_6_Hair_Converting_tutorial

GMH 2 GMH Hair Style Tutorial
1 CONTENT
2 Prepare polygon hair models ......................................................................................................................................................................................... 2
3 Create GMH Hair Style System ....................................................................................................................................................................................... 3
4 Convert polygon meshes to GMH Surface .................................................................................................................................................................. 3
5 Edit GMH Style System ..................................................................................................................................................................................................... 5
5.1 EDIT PFX SEGMENTS...................................................................................................................................................................................................... 5
5.2 EDIT SURFACE HAIR THICKNESS ( HAIR CLUMP PER EDGE LOOP )......................................................................................................................... 6
5.3 Duplicate & Convert workflow .................................................................................................................................................................................. 7
5.4 Edit Clump Width ......................................................................................................................................................................................................... 7
5.5 Edit Thinning ................................................................................................................................................................................................................. 8
5.6 Best practice ............................................................................................................................................................................................................... 9
5.7 Other settings ............................................................................................................................................................................................................. 10
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 1

2 Prepare polygon hair models
GMH2 is a script to convert polygon base
meshes to hair so you would need to create polygon
hair models before using GMH2. Open file
GMH2.6_tutorialFile001_basePolygonHairModel.ma
You will see a pre-made model with polygon hair
style, this is an example of how the hair model could
be setup to work with GMH2. It does not need to be
super detail, draft block-out meshes are good
enough for guiding GMH hair tubes.
The mesh model are already separated into two
groups "HairTop" and "HairBottom" so we can easily
select them part by part to convert.
Hair bottom group that goes around hair area 's border
Hair Top group that fill inside hair area
Tip : There are many ways to create base polygon hair models:
You can quickly
block out hair meshes
using NURBS curves in
Maya and convert
NURBS surface to
Polygon. See "Nurbs"
and "Curves" group in
the example file :
GMH2.6_tutorialFile001_
basePolygonHairModel.
ma
Using ZBrush 's Tube Brush
or Fiber Mesh with flat Tubes
settings. For detail workflow
please visit this link to tutorial
"ZBrush Maya Game Hair" by
Daniel Cahill
https://vimeo.com/8861
8744
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 2

3 Create GMH Hair Style System
Next step is to create a GMH Hair Style System to convert polygon meshes to GMH Surfaces.
Click on " Create GMH Style" and enter "RedHair" ( Or any
name you like ) as name of the new GMH Hair Style System (
Leave "polygon Style System" check box unchecked to create
GMH Hair style System").-Dont worry about the name, we will tweak the
hair system to red hair in rendering tutorial later!
Click on "RedHair_GMHHairStyleSystem" on GMH2 window
to set it as current GMH Style System.
4 Convert polygon meshes to GMH Surface
Select one of the hair base mesh and click "Apply GMH Style", GMH will convert it to GMH Surfaces with Maya
Hair growing on the surface.
Go through the rest of the hair base meshes to convert all hair meshes to GMH Surfaces. There might be some
surfaces converted in wrong direction, you have to click on "rotate" button to rotate the direction of the hair on
GMHSurface .
Multiple surfaces can be selected and rotate/convert at the same time.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 3

Move the HairTop group aside so we can
select and convert the HairBottom group
easily.
Select all hair base Mesh in the
HairBottom group.
Click "Apply GMHStyle" to convert all
selected meshes to GMH Surfaces.
Select surfaces that are currently in wrong direction, and click "rotate" until they are in correct direction.
-Note: You can use the "Reverse" button to
quickly reverse the hair direction 180*.
Note:
-You can carry on poly editing on those converted GMH Surface such as: Extrude, Insert Edge Loops, Bevel ( except combine and
extract/separate), Assigning deformers like latice-FFD, wave, squash etc as long as the grid topology is maintained.
-GMH Surface 's hair tubes will automatically follow and take shape of the new meshes shape.
-Delete histories of converted surface are also safe.
Important:
-The mesh name has to be unique in the scene otherwise GMH will not recognize the surface. Make sure you
have clean up the scene and rename/delete histories of all the base mesh properly.
-Make sure the timeline are at frame 1 or 0 otherwise GMH Surface 's hair will not update to follow the base
surface.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 4

5 Edit GMH Style System
When we have converted all meshes to GMH Surface and rotate them in
right direction, the next step is to tweak GMH Hair Style System and individual
GMH Surface settings. Open up the next file in tutorial_files folder :
GMH2.6_tutorialFile003_convertToGMHSurface.ma
You will see a hair models fully converted to GMH Surface.
5.1 EDIT PFX SEGMENTS
Looking closely at the hair clumps generated on GMH Surface, you will notice that the hair clumps are not follow closely the
original meshes, there is a straight line/ stiff segment at the root of the clump.
This is because of the default value ( 10 segments ) of PFXBrush Segments in GMH Hair Style System. Increase this value to
make hair clumps having more segment to follow original surface closer.
Select "RedHair_GMHHairStyleSYstem" in GMH2 window and click on "Edit GMH Style" button to edit its setting. Scroll down to
RedHair_PFXBrush section, increase Segments to 30.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 5

5.2 EDIT SURFACE HAIR THICKNESS ( HAIR CLUMP PER EDGE LOOP )
Rotate camera to back of the hair mode, the main GMH Surface that make up most of
back head area has very loose density of hair clump.
Because GMH generate hair clump base on number of edge loop of the original mesh
surfaces. The attribute " Hair Tube Num" in PFXBrush section control the number of hair clump per
edge loop will be generated. By default it's 5 mean there will be around 5 clumps will be generated
for each edge loops of the original meshes.
However it is not good for all GMH
Surface sharing the same density of hair
clump per edge loop, you might want to
assign different hair clump density to
some surface
( For example: denser hair clump for
bigger surfaces at the back of the hair
model and looser hair clump for smaller
surfaces around forehead.)
Select the surface you want to make it thicker and click "Thicken" button under "Surface Edit" tab to override/increase
the hair clump per edge loop of selected GMH Surfaces. You might need to click it several time before the GMH Surface
have enough hair clumps density thickness. Same workflow is applied for GMH Surfaces you want to make it thinner by
clicking the button "Thinning".
Note: If you have to click thicken so many time before it get the right density, there is a shorter way to do it by directly adjust
the override "GMH Clump Per Edge Loop" attributes under "Extra Attributes" section of GMH Surfaces. After editing the value ,
you have to re-apply GMHStyle to it again so GMH will re-create the GMH Surface with new Clump Per Edge Loop value.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 6

5.3 Duplicate & Convert workflow
Select one of the front forehead hair GMH
Surface, hit Ctrl+d to duplicate it and rotate it
slightly to make another hair surface growing
along side by side to the first one.
Click "Apply GMH Style" to convert it to
GMH Surface
Click "thinning" to make it thinner
Repeat the same process for other part of the hair model untill you got a more detail hair model.
5.4 Edit Clump Width
Hair root in forehead area are looking
stiff and unnatural,
Same for hair tip at the back
Tweaking Clump Width Scale in GMH Style System
can solve this issue.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 7

5.5 Edit Thinning
Maya Hair Thinning is to control the amount of hair trans got cut off toward the end/ tip of a hair clump.
For each GMH Surface you could control the amount of thinning by adding more edge loop at the tip or root of base polygon mesh.
Thinning = 1.0
No edge loop was added
Thinning = 1.0
Edge loop added at the tip Thinning = 1.0
Edge loop added at the root
Using edge loop you could control the amount of thinning of GMH Surface at the back of the head, making them denser at the end.
Adding 1 edge loop
Adding 3 more edge loops
Note: Sometimes, adding edge loop to a GMH Surface may cause the direction of hair tube to change, simply rotate the hair direction
again using the "Rotate" button in GMH2 window.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 8

5.6 Best practice
Now you have finished converting and tweaking your hair model .Open file : GMH2.6_tutorialFile004_tweak.ma for final hair model file
with edited GMH Style System and GMH Surfaces.
Time to wrap it up and move on to rendering & dynamic. There are some notes to remember while converting:
-Put original hair meshes together under separated group for easier selection and converting.
-Assign unique name to each hair meshes to avoid GMH2 bug while converting.
-Delete Histories are safe for original Hair meshes.
-Do not delete histories of GMH Style System node otherwise all connection and expression inside GMH Style System Node will be broken.
-The base mesh name has to be unique in the scene otherwise GMH will not recognize the surface. Make sure you have clean up the scene
and rename/delete histories of all the base mesh properly.
-Make sure the timeline are at frame 1 or 0 otherwise GMH Surface 's hair will not update to follow the base surface.
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 9

5.7 Other settings
There are many other attributes to work with hair styling inside GMH Hair Style System Node, this tutorial will only cover some of the most
important settings that are essential to style the hair .
If you want to know more about these settings please take a look at
Autodesk Maya Hair System Node:
http://help.autodesk.com/view/MAYAUL/2015/ENU/?guid=Hair_Nodes_hairSystemShape
Autodesk PFX Brush :
http://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/Maya/files/Paint-Effects-and-3D-
Paint-Windows-and-Editors-Paint-Effects-Brush-Settings-htm.html
Geometry To Maya Hair 2 Quick Start Guide
BY PHUNG DINH DZUNG
Page | 10