Add rendering functionals

CHANGELOG.md

@@ -60,6 +60,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added geometry functionals in `physicsnemo.nn.functional` for
   `mesh_poisson_disk_sample`, `mesh_to_voxel_fraction`, and
   `signed_distance_field`.
+- Added rendering functionals in `physicsnemo.nn.functional` for isosurface,
+  mesh, volume, LIC, point cloud, wireframe, and RGBA transfer rendering, with
+  Warp kernels for rendering and PyTorch fallbacks for transfer functions.
 - Adds embedded OOD guardrail `OODGuard` at
   `physicsnemo.experimental.guardrails.embedded`, optionally
   wired into `GeoTransolver` via a new `guard_config` constructor argument.

docs/api/nn/functionals/rendering.rst

@@ -0,0 +1,81 @@
+Rendering Functionals
+=====================
+
+Rendering functionals convert tensor fields and geometric primitives into image
+buffers. They follow the same stateless functional pattern as the rest of
+``physicsnemo.nn.functional``: tensors in, tensors out, with implementation
+dispatch handled through ``FunctionSpec``.
+
+Isosurface Render
+-----------------
+
+.. autofunction:: physicsnemo.nn.functional.isosurface_render
+
+.. rubric:: Visualization
+
+This animation ray-marches a moving sphere isosurface from a scalar field and
+colors the hit surface with an RGB volume.
+
+.. figure:: /img/nn/functional/rendering/isosurface_render.gif
+   :alt: Isosurface render animation of a moving sphere
+   :width: 55%
+
+Mesh Raycast
+------------
+
+.. autofunction:: physicsnemo.nn.functional.mesh_raycast
+
+.. rubric:: Visualization
+
+This animation renders a rotating cube mesh with per-vertex colors.
+
+.. figure:: /img/nn/functional/rendering/mesh_raycast.gif
+   :alt: Mesh raycast animation of a rotating colored cube
+   :width: 55%
+
+Scalar Field To RGBA
+--------------------
+
+.. autofunction:: physicsnemo.nn.functional.scalar_field_to_rgba
+
+Line Integral Convolution
+-------------------------
+
+.. autofunction:: physicsnemo.nn.functional.line_integral_convolution
+
+.. rubric:: Visualization
+
+This animation shows a zoomed-out center slice through a 3D LIC field computed
+from a rotating dipole vector field. The LIC texture modulates a jet-colored
+field-magnitude image after starting from fixed random noise.
+
+.. figure:: /img/nn/functional/rendering/line_integral_convolution.gif
+   :alt: Line integral convolution animation of a rotating dipole field
+   :width: 55%
+
+This animation renders a steady 3D dipole LIC field as an RGBA volume with
+``volume_render`` and overlays a rotating wireframe cube for spatial context.
+
+.. figure:: /img/nn/functional/rendering/line_integral_convolution_3d.gif
+   :alt: Three-dimensional line integral convolution volume render with rotating cube
+   :width: 55%
+
+Vector Field To RGBA
+--------------------
+
+.. autofunction:: physicsnemo.nn.functional.vector_field_to_rgba
+
+Volume Render
+-------------
+
+.. autofunction:: physicsnemo.nn.functional.volume_render
+
+Point Cloud Render
+------------------
+
+.. autofunction:: physicsnemo.nn.functional.point_cloud_render
+
+Wireframe Render
+----------------
+
+.. autofunction:: physicsnemo.nn.functional.wireframe_render

docs/api/physicsnemo.nn.functionals.rst

@@ -24,3 +24,4 @@ in the documentation for performance comparisons.
    nn/functionals/fourier_spectral
    nn/functionals/regularization_parameterization
    nn/functionals/interpolation
+   nn/functionals/rendering

physicsnemo/nn/functional/__init__.py

@@ -43,6 +43,16 @@
 from .natten import na1d, na2d, na3d
 from .neighbors import knn, radius_search
 from .regularization_parameterization import drop_path, weight_fact
+from .rendering import (
+    isosurface_render,
+    line_integral_convolution,
+    mesh_raycast,
+    point_cloud_render,
+    scalar_field_to_rgba,
+    vector_field_to_rgba,
+    volume_render,
+    wireframe_render,
+)
 
 __all__ = [
     "irfft",
@@ -52,8 +62,11 @@
     "imag",
     "interpolation",
     "knn",
+    "isosurface_render",
     "legendre_polynomials",
+    "line_integral_convolution",
     "mesh_green_gauss_gradient",
+    "mesh_raycast",
     "meshless_fd_derivatives",
     "mesh_lsq_gradient",
     "mesh_poisson_disk_sample",
@@ -68,12 +81,17 @@
     "rectilinear_grid_gradient",
     "rfft",
     "rfft2",
+    "point_cloud_render",
+    "scalar_field_to_rgba",
     "signed_distance_field",
     "smooth_log",
     "spectral_grid_gradient",
     "spherical_basis",
     "uniform_grid_gradient",
+    "vector_field_to_rgba",
     "vector_project",
+    "volume_render",
     "view_as_complex",
     "weight_fact",
+    "wireframe_render",
 ]

physicsnemo/nn/functional/rendering/__init__.py

@@ -0,0 +1,46 @@
+# SPDX-FileCopyrightText: Copyright (c) 2023 - 2026 NVIDIA CORPORATION & AFFILIATES.
+# SPDX-FileCopyrightText: All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from .isosurface_render import IsosurfaceRender, isosurface_render
+from .line_integral_convolution import (
+    LineIntegralConvolution,
+    line_integral_convolution,
+)
+from .mesh_raycast import MeshRaycast, mesh_raycast
+from .point_cloud_render import PointCloudRender, point_cloud_render
+from .scalar_field_to_rgba import ScalarFieldToRGBA, scalar_field_to_rgba
+from .vector_field_to_rgba import VectorFieldToRGBA, vector_field_to_rgba
+from .volume_render import VolumeRender, volume_render
+from .wireframe_render import WireframeRender, wireframe_render
+
+__all__ = [
+    "IsosurfaceRender",
+    "LineIntegralConvolution",
+    "MeshRaycast",
+    "PointCloudRender",
+    "ScalarFieldToRGBA",
+    "VectorFieldToRGBA",
+    "VolumeRender",
+    "WireframeRender",
+    "isosurface_render",
+    "line_integral_convolution",
+    "mesh_raycast",
+    "point_cloud_render",
+    "scalar_field_to_rgba",
+    "vector_field_to_rgba",
+    "volume_render",
+    "wireframe_render",
+]

physicsnemo/nn/functional/rendering/isosurface_render/__init__.py

@@ -0,0 +1,19 @@
+# SPDX-FileCopyrightText: Copyright (c) 2023 - 2026 NVIDIA CORPORATION & AFFILIATES.
+# SPDX-FileCopyrightText: All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from .isosurface_render import IsosurfaceRender, isosurface_render
+
+__all__ = ["IsosurfaceRender", "isosurface_render"]