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Required For Houdini 16 Fur:
In hairgen object's Render tab, we need to set Hair Generation to Use SOP Geometry so RiCurves will be generated. Otherwise, no fur will be rendered.
Render Fur
To render Houdini fur with RenderMan, we need to add the required RenderMan curve attributes and use the PxrMarschnerHair hair Bxdf.
Add Curves Attributes
For Houdini 15.5, select the fur object node (e.g. the fur node inside grid_object1_fur), add the following RenderMan attributes.
For Houdini 16, add these attributes to the hair gen node. See Curves for more information on these attributes.
- ri_roundcurve - This turns on/off round curves. It is off by default which will render as flat ribbons.
- ri_curveinterpolation - This selects whether the curve is linear or cubic.
- ri_curvebasis - This selects the basis of the curve such as B-spline.
For cubic bezier curve interpolation, we need to set the Guide Groom node's Guide Creation/Segments as a multiple of 3, e.g. 3, 6, 9, etc.
For hair, it is also recommended to add the following attribute.
- ri_dicehair - This turns on/off the hair dicing.
Add Curves Option
For ROP, it is recommended to add ri_hairminwidth which sets the minimal width for the hair.
Create and Assign the Hair Shader
Dive into the fur's shopnet. Create a RIS Network and PxrMarschnerHair inside the RIS Network.
Set the Material of the fur object to point to this shader path.
Display
Turn off display for other nodes so only fur is displayed.
Add Width Attribute
Like rendering normal Curves in Houdini, we also need to add a width attribute.
- Add a width attribute with Attribute Create. Set its type to Vertex Float. Set a width value at the bottom, e.g. 0.05.
- Map the width attribute to RenderMan attribute with Attribute Rename.
- For H16.0, connect the attribute create and rename nodes after the set_width node inside the Hair Generate node.
- For H15.5, connect the attribute create and rename nodes after the create_fur node.
