Houdini 16.5 Nodes Object nodes

Fur object node

Creates fur geometry for rendering with a Mantra Fur Procedural.

On this page

Overview

The Fur object creates fur rooted on the specified skin geometry.

Note

You need UV coordinates when using any of the texture map parameters. See UV Texture.

Tips

  • Memory usage can be reduced by transferring values as primitive attributes from the skin instead of point/vertex attributes from the guides.

  • The Radius parameter on the Guide tab affects how big of an area is influenced by each guide hair. You can also create a primitive attribute called for more control. If this value is too small, some hairs might not have any guide hairs influencing them. If the value is too big, the effect of individual guide hairs will be difficult to see.

  • The guides subnet inside the Fur Object creates the initial guide hair curves. This network can be replaced with one defining hand-modeled guides. There are a few items to keep in mind when creating this network:

    • The guides are used as the rest pose of the wires and needs to be deformed to match animation on the skin.

    • The guides should have a primitive attribute called guideorigin indicating where the guide attaches to the skin in its rest position.

    • If you are adding dynamics, a point attribute called pintoanimation should be used to constrain the root point of each curve.

Parameters

Basic

Display

Whether or not this object is displayed. Turn on the checkbox to have Houdini use this parameter, then set the value to 0 to hide the object, or 1 to show the object. If the checkbox is off, Houdini ignores the value.

Type

Type of geometry to create.

Polygon

Create a polyline.

NURBS

Create a NURBS curve.

Subdivision Curves

Create a polygon curve. This is much faster than NURBS.

Length

Specifies the length of the generated curves.

Segments

Number of segments in each generated curve (ignored if geometry is provided by the Guides input)

Distribution Seed

Seed value for the random number generator

Display Density

The number of displayed curves is a result of the density multiplied by the area of the skin polygons. The value of this parameter acts as a scalar multiplier to the optional furdensity attribute to determine the curve density.

Display Ratio

Specifies a fraction of the curves to display.

Render Density

The number of rendered curves is a result of the density multiplied by the area of the skin polygons. The value of this parameter acts as a scalar multiplier to the optional furdensity attribute to determine the curve density.

Render Ratio

Specifies a fraction of the hairs to render.

Material

Path to the Material node.

Shade Fur in Viewport

It enables shaded open curve rendering in the viewport, which draws the hair curves as ribbons (instead of lines) and uses a hair-based lighting model for shading those curves.

Guides

Use Guides

When enabled, the shape of rendered hairs will be interpolated from the guide hairs.

Display

Whether or not the guide hairs are displayed.

Remove Unguided Hairs

Remove all hairs not influenced by a guide hair.

Color

Color used to draw guide hairs.

Guide Type

Place At Every Surface Point

Creates a guide at every point of the skin.

Scatter On Surface

Indicates guide hairs should be scattered across the skin instead of placed at points within the skin geometry.

Use External

Fetches guides from an external geometry. In this mode, additional parameters will be displayed below, which can be useful for fixing common errors in imported guide curves.

Note

These guides are expected to be static, so this is not the way to bring in simulated guides. To do this, please use the Add Dynamics shelf tool, or manually add dynamics in ./guide_dynamics within the Fur object.

Draw Guides Manually

Doesn’t generate any guides, instead allowing the user to create them from scratch, for example using tools on the Grooming Shelf.

Geometry

Path to an object containing guide geometry.

Resample To Match Fur Segments

Resamples external guides to match the Segments parameter.

Reverse Curves

When importing external guides, reverses the order of vertices within each each curve. This should be used when the root vertex is not the first vertex in the curve.

Snap To Skin

Moves external guides so the root sits exactly on the skin.

Distribution Seed

The seed value for the random number generator.

Density

The number of guide hairs is a result of the density multiplied by the area of the skin polygons. The value of this parameter acts as a scalar multiplier to the optional furdensity attribute to determine the curve density.

Relax Iterations

The number of relax iterations to perform when scattering guides. More iterations result in a more even distribution of guides.

Influence Radius

Maximum distance a hair can be from a guide hair and still be influenced by the guide hair.

Attributes

New Class

The class for transferred attribute.

Transfer Attributes

Specifies a list of attributes from the guide and clump curves that will be transferred to the generated curves. The resulting attribute values will contain any modifications made by CVEX shaders.

Length

Length Map

Specifies a texture map used to modulate the length of guide hairs.

Length Map Blend

Specifies how much the Length Map can modulate the length of each guide hair.

Comb

Comb Noise

Specifies how much additive noise to apply to the direction of each guide hair.

Comb Noise Map

Specifies a texture map used to modulate the amount of comb noise.

Comb Noise Map Blend

Specifies how much the Comb Noise Map can modulate the amount of comb noise.

Bend

Bend

Specifies how much a guide hair will bend in the combed direction.

NOTE: Guide hairs must be combed away from the normal or have comb noise applied for the bend direction to be well-defined.

Bend Map

Specifies a texture map used to modulate the bend of guide hairs.

Bend Map Blend

Specifies how much the Bend Map can modulate the bend of each guide hair.

Bend Noise

Specifies how much additive noise to apply when bending each guide hair.

Bend Noise Map

Specifies a texture map used to modulate the amount of bend noise.

Bend Noise Map Blend

Specifies how much the Bend Noise Map can modulate the amount of bend noise.

Twist

Twist

Specifies how much a guide hair will twist in the combed direction.

Twist Map

Specifies a texture map used to modulate the twist of guide hairs.

Twist Map Blend

Specifies how much the Twist Map can modulate the twist of each guide hair.

Twist Noise

Specifies how much additive noise to apply when twisting each guide hair.

Twist Noise Map

Specifies a texture map used to modulate the amount of twist noise.

Twist Noise Map Blend

Specifies how much the Twist Noise Map can modulate the amount of twist noise.

Hair Types

White

Distribution Seed

Seed value for the random number generator.

Ratio

Specifies a fraction of the hairs to become white hairs.

White Map

Specifies a texture map used to modulate the ratio of white hairs.

White Map Blend

Specifies how much the White Map will modulate the ratio of white hairs.

Guard

Note

Animals have a layer of longer coarse hairs which protect the softer fur underneath. These hairs are called guard hairs.

Distribution Seed

Seed value for the random number generator.

Ratio

Specifies a fraction of the hairs to become guard hairs.

Guard Map

Specifies a texture map used to modulate the ratio of guard hairs.

Guard Map Blend

Specifies how much the Guard Map will modulate the ratio of guard hairs.

Length Scale

Multiplier applied to the length of all guard hairs.

Width Scale

Multiplier applied to the width of all guard hairs.

Frizz Scale

Multiplier applied to the frizz of all guard hairs.

Appearance

Length & Density

Length Map

Specifies a texture map used to modulate the length of hairs.

Length Map Blend

Specifies how much the Length Map can modulate the length of each hair.

Randomize Length

Specifies the amount each hair’s length should be randomly scaled.

Density Map

Specifies a texture map used to modulate the furdensity attribute.

Density Map Blend

Specifies how much the Density Map will modulate the furdensity attribute.

Cut Map

Specifies a texture map used to cut the length of each hair. This is similar to the Length Map but will adjust the frizz to match cut hair.

Cut Map Blend

Specifies how much the Cut Map can affect each hair.

Displacement Map

Specifies a texture map used to displace the position of each hair.

Displace Direction

Specifies how to interpret values from the Displacement Map.

Displacement Scale

Scales the amount each hair is displaced by the Displacement Map.

Thickness

Thickness

Specifies how the width of each hair varies from the root to the tip.

Minimum Thickness

Specifies the minimum width of each hair.

Maximum Thickness

Specifies the maximum width of each hair.

Thickness Map

Specifies a texture map used to modulate the width attribute.

Thickness Map Blend

Specifies how much the Thickness Map will modulate the width attribute.

Frizz

Frizz

Specifies how the amount of frizz applied to each hair varies from the root to the tip.

Minimum Frizz

Specifies the minimum amount of frizz applied to each hair.

Maximum Frizz

Specifies the maximum amount of frizz applied to each hair.

Amplitude Map

Specifies a texture map used to modulate the frizz amplitude.

Amplitude Map Blend

Specifies how much the Amplitude Map can modulate the frizz.

Frequency

Specifies the frequency of the frizz noise. Frequency and roughness are two properties of the frizz noise. Frequency controls the number of oscillations of noise along a hair. Higher frequency values result in more oscillations. The effect of this tool is easier to see when the number of segments per hair is increased.

Tip

Use the Paint Frizz Frequency tool if you want to change the number of noise oscillations along the length of hairs and use the Paint Frizz Roughness if you want to change how smooth or rough each oscillation appears.

Frequency Map

Specifies a texture map used to modulate the frizz frequency.

Frequency Map Blend

Specifies how much the Frequency Map can modulate the frizz.

Roughness

Specifies the roughness of the frizz noise. Frequency and roughness are two properties of the frizz noise. Roughness can be thought of as a non-smooth component of the noise. The effect of this tool is easier to see when the number of segments per hair is increased.

Tip

Use the Paint Frizz Frequency tool if you want to change the number of noise oscillations along the length of hairs and use the Paint Frizz Roughness if you want to change how smooth or rough each oscillation appears.

Roughness Map

Specifies a texture map used to modulate the frizz roughness.

Roughness Map Blend

Specifies how much the Roughness Map can modulate the frizz.

Octaves

Specifies the octaves of the frizz noise.

Clump

Clump Fur

When enabled, all hairs are associated with the nearest clump hair.

Display

Whether or not the clump hairs are displayed

Color

Color used to draw clump hairs

Clump Geo Source

Controls how clump guides are generated.

Scatter

Scatter clump guides on the skin geometry.

Use Guide Curves

Reuse the guide curves for clumping.

Use External

Use An External SOP.

Geometry

Path to an object containing clump geometry.

Distribution Seed

Seed value for the random number generator.

Density

The number of clump hairs is a result of the density multiplied by the area of the skin polygons. The value of this parameter acts as a scalar multiplier to the optional furdensity attribute to determine the curve density.

Radius

Maximum distance a hair can be from a clump and still be a member of the clump.

Tightness

The amount each hair is pulled towards its associated clump.

Clump Profile

The profile shape for each clump.

Clump Map

Specifies a texture map used to clump hairs.

Clump Map Blend

Specifies how much the Clump Map can affect each hair.

Use Closest Clump

Associates each hair with its closest clump.

Remove Unclumped Hairs

Remove all hairs not associated with a clump.

Parting

Part Fur

When enabled, only guide hairs on the same side of parting lines are used influence the shape of hairs.

Display

Whether or not parting lines are displayed in the viewport.

Color

The color used to draw parting lines.

Radius

Maximum distance rest skin can be from a parting line and still be affected.

Dynamics

Use Ramps To Control Stiffness

Enables stiffness controls.

Bend

Stiffness

Specifies how the stiffness of each hair varies from the root to the tip.

Minimum Stiffness

Specifies the minimum stiffness of each hair.

Maximum Stiffness

Specifies the maximum stiffness of each hair.

Stretch

Stiffness

Specifies how the stiffness of each hair varies from the root to the tip.

Minimum Stiffness

Specifies the minimum stiffness of each hair.

Maximum Stiffness

Specifies the maximum stiffness of each hair.

Skin

Display Offset

Displacement offset used when displaying skin geometry.

New Class

Class for transferred attribute.

Transfer Attributes

Specifies a list of attributes from the skin geometry that will be transferred to the generated curves. The resulting attribute values will contain any modifications made by CVEX shaders.

Set Hair ID

Creates a hairid attribute containing a unique value for each generated curve.

Groom Frame

Specifies the frame used to compute the skin’s rest position.

Skin

Path to an object containing skin geometry.

Complete Group

Primitives in the skin geometry from which to groom hair.

Visible Group

Primitives in the skin geometry from which to grow hair.

Transfer Groom To New Skin

Method

The method to use for updating to a new skin. Use the Update From SOP button below to initiate the update.

Note

The Recache Strokes method below does not leave any record of the original skin, and it’ll appear like the groom was started on the current skin.

Recache Strokes (Changed Topology, Small Position Changes)

Performs the update by re-applying all recorded grooming strokes to guides generated on the new skin. This is the simplest method, and should be used if there have only been topology changes and the skin is otherwise very similar.

Note

The methods below will leave a clear history of updates in the guides subnet, where all grooming happens.

Transfer Direct (Changed Position)

Use this if there has been a change in position/scale/sculpting while the topology has remained unchanged.

Uses the Transfer Guides SOP to transfer an existing groom to a new skin. Existing grooming nodes are collapsed into a subnet and can still be edited.

Transfer By UV (Changed Position and Topology)

Use this if their has been a change in position/scale/sculpting and topology. This relies on a matching UV set between the current and new skin.

This is the same as Transfer Direct, except it does the transfer using a UV set that exists on both the old and new model. This means that in addition to position changes, the topology can also be dramatically different between models.

UV Attribute

The UV Attribute to use when Method is set to Transfer By UV.

Update From SOP

Update to a new skin geometry, using the options set above. This let’s you pick a SOP to use as the new geometry.

Render

Render Style

Controls how the fur is rendered in mantra.

Procedural

Generate curves at render time using the fur procedural.

Direct

Generate curves in Houdini before rendering and send the generated curves to mantra.

Phantom

If enabled, this object will only cast shadows and reflections.

Mantra

Bounding Box

The bounding box controls let you specify a bounding box for the referenced geometry. Only when this bounding box is "on screen" will mantra load the referenced geometry. You can set Bounding box to No bounding box required, in which case mantra will always load the references geometry regardless. You can also specify the bounding box by referencing the SOP’s bounding box in the SOP Bounds parameter.

SOP Bounds

The geometry whose bounding box you want to reference.

Min Bounds

The minimum bounding box dimensions, when setting explicit bounds.

Max Bounds

The maximum bounding box dimensions, when setting explicit bounds.

Expand Bounds

Allows you to adjust the bounds of the bounding box to compensate for any fur that may have been moved outside of the original bounds by a shader.

Shading

Categories

The categories defining the set membership of this object.

Reflection Mask

Space-separated list of objects to appear in reflections on this object. You can use wildcards (for example, prop_*) and bundle references to specify objects.

You can also use the link editor pane to edit the relationships between objects using a graphical interface.

Refraction Mask

Objects that will be refracted on this object.

Light Mask

Space-separated list of names of lights that illuminate this object. You can use wildcards (for example, key_*) and bundle references to specify objects.

You can also use the link editor pane to edit the relationships between lights and objects using a graphical interface.

Matte shading

Render the object as a cut-out matte.

Raytrace Shading

Shade every sample rather than shading micropolygon vertices. This setting enables the raytrace rendering engine on a per-object basis.

Sampling

Geometry Velocity Blur

If enabled, this object’s rendered motion blur will be based upon the vector attribute named v in the geometry. The units of the attribute are in (1 unit/sec).

Velocity motion blur should be used if it contains changing point counts since it cannot be rendered correctly with deformation motion blur. For example, a particle system with changing particle counts should use this option.

You can use Velocity blur on these types of objects as long as they have valid v attributes. Particles automatically have the v attribute so if you are rendering particles, simply enable this parameter.

Dicing

Shading Quality

Shading Quality is used by micropolygon rendering to control the shading resolution. A value of 1 means that approximately 1 micropolygon will be used per pixel. A higher value will generate smaller micropolygons meaning more shading and sampling will occur, but the quality will be higher.

Ray Shading Quality

Ray Shading Quality is used by raytracing when rendering. When raytracing subdivision surfaces or patch surfaces (eg. NURBS), geometry dicing will occur similar to micropolygon rendering. This value functions similar to Shading Quality for these primitives when raytracing.

Note

Only when rendering subdivision surfaces and patch surfaces (eg. NURBS) will this setting have an effect.

Geometry Filter Width

Geometry Filter Width sets a minimum rendering width in raster space for curves. Any curve segment smaller than this value at the projected point will instead have its opacity scaled down as a ratio of the minimum width and the actual width. This helps rendering very thin curves without having to adversely increase the pixel samples to compensate.

Dicing Flatness

This property controls the tesselation levels for nearly flat primitives. By increasing the value, more primitives will be considered flat and will be sub-divided less.

Ray Predicing

This property will cause this object to generate all the micro-polygons before the render begins. Ray tracing can be significantly faster at the cost of potentially huge memory requirements.

Shade Curves As Surfaces

When rendering a curve, turns the curve into a surface and dices the surface, running the surface shader on multiple points across the surface. This may be useful when the curves become curved surfaces, but is less efficient. The default is to simply run the shader on the points of the curve and duplicate those shaded points across the created surface.

Geometry

Backface Removal

If enabled, geometry that are facing away from the camera are not rendered.

Polygons As Subdivision

If enabled, polygon geometry rendered from this object will be rendered as a subdivision surface.

Render As Points

By default, points within particle system primitives are rendered as sphere primitives. If a point is not part of a particle system primitive, then it is not rendered. If this parameter is enabled, then all points (regardless if they are part of a particle system) from this object’s geometry will be rendered as point (circle) primitives facing the camera plane.

Coving

Coving is the process of filling cracks in diced geometry at render time, where different levels of dicing side-by-side create gaps at T-junctions.

The default setting, Coving for displacement/sub-d, only does coving for surfaces with a displacement shader and subdivision surfaces, where the displacement of points can potentially create large cracks. This is sufficient for more rendering, however you may want to use Coving for all primitives if you are using a very low shading rate or see cracks in the alpha of the rendered image.

Do not use Disable coving. It has no performance benefit, and may actually harm performance since Houdini has to render any geometry visible through the crack.

This setting only applies to micropolygon rendering.

Automatically Compute Normals

If enabled, smooth normals will we computed at render time if the normal (N) vector attribute does not exist.

See also

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  • Guide Deform

    Moves the curves of a groom with animated skin.

  • Guide Groom

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  • Guide Simulate

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  • Mocap Biped 1

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  • Mocap Biped 2

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  • Mocap Biped 3

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  • Pxr Portal Light

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  • Pxr Rectangle Light

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  • Simple Biped

    A simple and efficient animation rig with full controls.

  • Simple Female

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  • Simple Male

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    Provides parameters to manipulate the interaxial lens distance as well as the zero parallax setting plane in the scene.

  • Stereo Camera Template

    Serves as a basis for constructing a more functional stereo camera rig as a digital asset.

  • Sticky

    Creates a sticky object based on the UV’s of a surface, usually for parenting.

  • Subnet

    Container for objects.

  • Switcher

    Acts as a camera but switches between the views from other cameras.

  • Tissue Solver

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  • VR Camera

    Camera supporting VR image rendering.

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  • pxr Int Mult Light Filter

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