Part 6: completing the whole hair
Now you need to apply the brush to all hair strokes on the other side of the skull and a little in front. Select hair_split_curve02, PaintEffects->Curve Utilities->Attach Brush to Strokes, while the new stroke is selected shift select all
the control_curves for the other side, PaintEffects->Curve Utilities-> set Stroke Control Curves, just like we did previously. Now select the new_stroke created then shift select the hair_side_stroke01, PaintEffects->share One Brush, this
will allow you to have one brush(hair_side_brush) to control both strokes of the hair. For the front hair, we are going to use separate brush for optimization later, select the original front_hair_split_curve, do a Attach Brush to Strokes and then Set Stroke Control Curves, to grow out the hair again. Rename this new stroke to hair_front_stoke. Now select the hair_side_stroke01, PaintEffects->Get Setting from selected stroke, then select hair_front_stroke, PaintEffects-> apply setting to selected strokes. Now the brush for hair_front_stroke will be the same as hair_side_brush, look at the hypergraph view screen shot below for connection reference. (Note: if your hair design is different on the other side of the skull then you'll need to use a separate brush eventually, just transfer the brush setting from the previously tweaked to the new one, and start tweaking from there). You should also assign a different hair texture for the front hair, if you are working with textures.
Part 7: Optimizing your hair
Right now the hair at the front don't look right and the side still lacks volume, for what I want. We are going to optimize both brushes of hair and make them not only faster to render but also take more volume. You don't have to crank up a lot of tubes per step to achieve more volume in your hair. Select the hair_front_brush, open up attribute editor, tubesPerStep=10,try even lower as there's less need for the front, the trick is to have a high width1 so that it doesn't really represent each strand of hair, but a bunch, you can do each strand with a texture map. Also lower segments=24, or less if the hair still looks smooth. Open the tab Behavior|forces, curveAttract = -0.041, this spread the hair away from a little the control curves, so a lot of the hair don't just stick close together near a single control curve. Select the hair_side_brush and also put a negative curveAttract value, I used -0.050. Now your hair should look more natural, to add more randomness play with the seed value and tube Rand values in the stroke.shape Node and brush NodeWe all know human hair don't grow evenly in volume because we cut them, for example some hair in front will be sparse and back will be more dense, or the side maybe more dense then the back. We can't just crank up the tubesPerStep, that will make overall the hair dense. We'll need to use a pressure curve to tell Paintfx where we need more hair. Pressure curves can be applied to many other parameters to optimize and achieve the effect you are after. Select the hair_side_stroke01, PaintEffects->CurveUtilities->makePressureCurves/option, change the control points=10 and offset scale=0.05, a curve should be created next to your stroke, if the Pressure curve is too close or far you'll need set a different offset Scale, to delete it, open up the pressure Mapping tab under the stroke.shapeNode, then right click pressureMin3, deleteExpression, then delete the pressure curve its self. If you have got a nice pressure curve near hair_side_stroke01 then open pressreMapping tab and set pressureMapping1=tubes Per Step, set pressure min1=0.1 and pressureMax1=1. Turn off other pressureMappings to stop unexpected results. Now you'll need to adjust the CVs on the pressureCurve, move the points in the middle of the curve more up higher then the rest(right). If you don't see any change to the density of hair on the side then change the pressureMin1 a little then it should update. Also lower the CVs the at the two ends of the curve to have less density in front and back. Test render different position for the CVs, using same camera angle and using the slider below the renderView to see the difference. Once you are satisfied, make a pressureCurve for hair_side_stroke02. Here's my render after optimizing with pressure curves.
That's all, you now have good control over your designed hair. There's some very important details that I missed. You maybe wandering, you can't animate this!, true, to add dynamics is very easy after you have the control_curves set. You can use several techniques to drive the motion of hair_control_curves, mel/expression/softbodies/clothObjects. For a clothObject approach take a look a Duncan Brinsmead's tutorial here, it uses cloth dynamics to drive the curves, all you need to to do is use the control curves we already made to produce the cloth objects. Another aspect is lighting, specular and shadow I did not talk about, that you can look into it your self. This is because to have good light/shadow not only requires working with pfx settings but also lights themselves, so its beyond the tut.
I hope you now understand the ideas behind how to use pfx not only for hair but other objects that takes similar form. The trick is using one stroke and some control_curves to shape that stroke to take on the form and let Pfx fill out the in betweens. I hope you had as much fun reading it as me making this tutorial...yeah..right... :) If you have any question
or suggestions please e-mail me firstname.lastname@example.org