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This node is a tool for creating guide curves for any type of groom.
Grooming radial menu
When using the Guide Groom SOP, make sure to switch to the Grooming radial menu from the top menu bar. This menu lets you quickly switch tools options in the viewport, and is the recommended workflow when using this node.
After switching to the Grooming radial, you can open it by pressing C. This brings up a menu that contains all the Tool options for the Guide Groom SOP, and reflects the options available in the Tool dropdown parameter on the node. It’s a quick way to switch between the options on this node.
For example, if you hover your mouse over Create & Move, you will see the 4 options available for creating and moving hair. You can either choose one, or navigate back to the previous level by hovering your mouse over the double arrows.
Each Tool has a Tool Options menu that is unique to that mode. For example, the tool options available in Draw mode are different than the ones available in Plant mode.
This section documents tools available in Guide Groom’s viewport state via the radial menu described above.
Create & Move
Draw individual hair curves.
Click and drag on the character’s skin and draw out from it to create a hair curve.
Various options are available to modify the drawing behavior. You can draw the entire hair on the character’s skin by enabling Draw on Skin.
Draw parting lines by changing Curve Type to.
The number of curve segments created is governed by the Segment Mode parameter. Set this to
Fixed to create hairs with a predefined number of segments. Set it to
Adaptive in order to create more segments for longer curves.
Click on the characters skin to create a hair at that point.
To create many hairs, switch to Scatter Mode and set the Radius and Density parameters. MMB Deletes curves under the brush.
To match the shape of surrounding hairs, enable Interpolate Guides. With this disabled (or when there are no hairs), the new hair will simply stick out straight from the surface. Length is then controlled by the Default Length parameter.
Interpolate Relative to Skin will interpolate surrounding hairs but rotate the created hair to match the clicked point’s skin curvature.
Move points around the character skin.
To rotate points with the curvature of the skin, enable Rotate with Skin
Evens out spacing between hairs. You can control the amount of space using the Density parameter.
Deletes hair under the brush.
Deletes hair until the density matches the Density parameter.
Smooths the shape of curves, removing any high frequency detail.
The higher the Smoothness parameter, the more details are smoothed out.
Clumps together any curves under the cursor. You can do this for the entire curve at once or in a more controlled way using Per Point.
MMB Separates the curves.
Sculpt curves by clicking and dragging.
Sculpt with Physics
Brush hair while simulating using Vellum physics.
Enable Live Simulation to run the simulation at all times, even while not actively brushing.
Use Settle Mode to drop hair under gravity.
Use Damped Mode to get the effects of physics simulation, with hair floating weightlessly.
Blends (averages) the shapes of hair under the brush.
Brush & Edit
Attempts to fix skin intersections, where part of the hair dives under the character’s skin.
Use this tool to move curves or individual points using a transform handle.
Soft Transform softly transforms the entire curve or part of it, depending on the Soft Transform Mode.
⇧ Shift & Drag on the handle to clone curves. You can also clone end points to extend the curve.
After doing this, you may use Shift+D to redistribute points evenly along the curve. Or use Shift+R to resample to a different segment count.
Brushes hair, rotating from the root.
You can also bend hairs by increasing the Bend parameter. The shape of the bend is the controlled by the Bend Falloff.
In Add / Subtract Mode, LMB to increase length, MMB to decrease.
Set Mode adjusts length until it matches the Length parameter.
With the Scale Method, the hair shape simply scales uniformly.
With the Cut / Extend Method, hairs are extended or trimmed at the tip.
Changes the orientation of hairs relative to the skin plane.
In Add / Subtract Mode, LMB raises and MMB lowers.
In Set Mode, hair is rotated until the angle matches the set Angle parameter.
Straightens the entire hair shape into a straight line, keeping the original length.
Group & Mask
Paint Group Tool
By default, this paints the currently set Active Name onto curves, but you can also change parameters under the Groups header to add brushed curves to a group instead.
Paint Mask Tool
Paint a mask attribute. Other tools use this to limit their effects to the painted region. The mask can be painted per point by enabling Paint Points.
LMB Adds to the mask, MMB removes.
For more information, see the Creating and styling guide hair with Guide Groom page.
Clears all edits, which resets back to the unmodified input or no geometry at all if no input is connected.
The currently selected elements to be groomed.
The element type of the current selection.
Reduces the effect of brushes and tools based on a painted mask. Use the Paint Mask tool to modify this mask.
You’ll also find mask related tools in the Grooming Radial Menu
The currently selected tool. The most convenient way to switch between tools is by using the Grooming Radial Menu.
The thickness of the collision layer around the character’s skin. The Guide Groom SOP prevents curves from passing through this outer layer while you edit them.
The ideal value would be something like 1/10th or 1/100th of the shortest segment length in a groom. Making it much larger would keep curve points at a large distance from the skin. Making it too small would make it easier for curves to end up inside the skin.
Edit Selection as Clump
Brushing the selection will modify it as a whole, as if all selected curves were clumped together. This makes it easier to preserve the volume of existing clumps while sculpting.
Collide with Skin
Prevents guides from passing through the character’s skin. It can be useful to turn this off in certain situations. For example, when guide are already stuck inside the skin and you want to move them back out.
Brush on the character’s surface. When this checkbox is turned off, the brush is in screen space. Most tools work either way, but for some tools such as Plant, this is always enabled since it only makes sense to plant guides on the surface of the skin.
Respect Parting Lines
When this checkbox is turned on, a brush will only affect guides on the cursor’s side of a parting line. This only works when Surface Brush is turned on, because the brushes' projected skin location is used to determine which side it is on.
The brush radius in pixels, when Surface Brush is turned off.
The brush radius in Houdini units, when Surface Brush is turned on.
The strength of the brush effect.
The softness of the brush shape.
When this is non-zero, the brush will be splatted at regular pixel intervals, regardless of how fast you move the cursor. This only works when Surface Brush is turned off.
Apply operation per point rather than per curve.
The amount the the length of curves is preserved while brushing. Values lower than 1 allow you to modify curve lengths by brushing along the curve.
Values over 0 cause curves to bend more as you brush them, rather than just rotating from the root.
Higher values cause curves to bend more at the tip, lower values cause them to bend more easily at the root.
Rotate with Skin
Rotates curves with the skin curvature as you move them.
Constrain the length of curve segments as you sculpt.
Locks the root in place as you sculpt.
Add / Subtract
Continuously lifts the curve of the skin as you keep brushing.
Lifts to a set amount.
Paint the mask values for individual points rather than curves as a whole.
The target angle for the lift tool.
Add / Subtract
Continuously Add to LMB or Subtract from MMB the curve length.
Adjust towards a predetermined absolute length as you brush.
The value to adjust by.
The length to adjust towards.
Cut / Extend
Cuts or extents at the tip, matching the tip direction.
Scales the entire curve, maintaining its shape.
Plants a single curve at the initial click location.
Scatters curves in a radius
The number of curves to scatter per square unit.
The length of planted curves. This is ignored when Interpolate Guides is turned on, as the curves will match the shape and length of nearby guides.
Blur Relative to Skin
Preserve the orientation of curves relative to the skin.
Plant curves with this number of segments.
Interpolate the shape of nearby guide curves.
Interpolate Relative to Skin
When interpolating guides, also maintain the shape’s orientation relative to the character’s skin.
Draw regular guide curves.
Draw parting line on the character’s skin.
Draw on Skin
Draw guides on the character’s skin. With this turned off, the first point drawn will sit on the skin, but subsequent points are drawn in the screen plane.
Draw guides with a fixed number of segments.
Create more segments as you draw longer curves, trying to match the Segment Length set below.
The number of segments when Segment Mode is set to Fixed.
Bend & stretch constraints are computed, but hair doesn’t drop under gravity.
Full physics simulation including dropping under gravity.
Simulate even while not actively brushing
An overall scale applied to the simulation timestep. Greater values slow down the simulation.
The gravity vector.
Constrain Root Orientation
Constrains the orientation of the first curve segment.
The strength of the physics brush.
Controls the bend resistance of the simulated hair.
Controls the stretch resistance of the simulated hair.
Set Rest State
Sets the rest state to the current simulation state. Once you do this, you can jump back to other tools and back to Sculpt with Physics, and hair will not drop or settle further.
Clear Rest State
Clears any set rest state.
Resample with a fixed number of segments per curve.
Resample such that a given segment length is matched, placing as many curve segments as necessary.
Adds a new point between two existing points.
Removes all points except root and tip and results in a straight line.
The number of desired segments.
The desired segment length.
The overall angle in degrees.
Enable live mirroring.
The group of primitives to mirror.
Origin point used for mirroring.
Direction vector of the mirror plane.
Preview the result of the utility.
Bake the result of the current parameter values into the groom.
Invert mask values.
Delete the mask attribute, clearing any previously painted values.
Curve Mask Ramp
Add New Curves to Group
Add newly created primitives to a group.
The group to add newly created primitives to.
Add Selection to Group
Add the current selection to the Active Group.
Delete the Active Group. This does not delete the curves contained in the group.
Hide curves in the current selection.
Unhide all curves.
Set Name on New Curves
Set a name attribute on newly created curves.
The name of the name attribute itself. The actual name of curves (i.e. the values of the attribute) are set using the Active Name parameter.
Newly created primitives will be set to this name when Set Name on New Curves is turned on.
Set Name on Selected Primitives
Sets selected primitives to the Active Name.
Select Primitives With This Name
Selects any primitives whose name matches Active Name.
Color Primitives by Name
Randomly colors primitives based on their name.
Random Color Seed
A seed value for the randomly generated colors.