Tree — attribute nodes
======================

**Attribute nodes** are :class:`Unary` scene nodes: each wraps a **child** subtree and changes how **continuous attributes** are produced or post-processed for that geometry. They are not the same thing as attaching an :class:`Attribute` with :meth:`Node.set_attribute`—that API defines field values on a node (see :doc:`attributes`). Attribute nodes instead implement **attribute-side operators** in the tree: converters, lookup tables, or spatial filters that sit between evaluation and the rest of the pipeline.

:class:`AttributeModifier` applies an **attribute converter** (for example, mapping one named field into another, such as HU to RGBA via a lookup table). :class:`Convolve` and :class:`Blend` spatially filter attribute samples **without** altering the signed-distance geometry of the child.

Unary attribute nodes
---------------------

.. currentmodule:: pyvcad

.. autoclass:: AttributeModifier
   :members:
   :undoc-members:
   :special-members: __init__

.. autoclass:: Convolve
   :members:
   :undoc-members:
   :special-members: __init__

.. py:class:: Blend(child, attributes, physical_radius, num_passes=1, override_voxel_size=None)

   Precompute selected child attributes on a voxel grid and apply a masked,
   separable box blur. This node leaves the child's signed-distance geometry unchanged.

Convolution kernels
-------------------

Kernels describe the spatial stencil :class:`Convolve` uses (uniform box averaging or explicit per-voxel weights).

.. autoclass:: ConvolveKernel
   :members:
   :undoc-members:
   :special-members: __init__

.. autoclass:: BoxKernel
   :members:
   :undoc-members:
   :special-members: __init__

.. autoclass:: CustomKernel
   :members:
   :undoc-members:
   :special-members: __init__