{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "\n# Faux Volume Rendering\n\nThis example demonstrates a technique for simulating volumetric rendering of\ncoronal density by deconstructing a 3-D\n:class:`~pyvisual.core.mesh3d.SphericalMesh` into stacked semi-transparent\nradial shells \u2014 a *faux* volume that avoids the GPU memory cost of true\nvolumetric rendering while still conveying the large-scale 3-D structure of\nthe corona.\n\nThe scene is animated along a Parker Solar Probe (PSP) trajectory\nobtained from the JPL Horizons ephemeris service via\n:func:`~pyvisual.utils.geometry.spacecraft_trajectory`, placing the virtual\nobserver at each spacecraft position and framing the field of view in\nhelioprojective angular coordinates using\n:attr:`~pyvisual.core.mixins.ObserverMixin.observer_los_view`.\n\n.. seealso::\n\n `sphx_glr_gallery_04_observer_mixin_p02_orbit.py`\n Simpler orbit animation driven by a synthetic observer path.\n\n `sphx_glr_gallery_99_advanced_plots_p01_combining_multiple_elements.py`\n Multi-layer coronal scene that combines slices, contours, and fieldlines.\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false }, "outputs": [], "source": [ "import os\nfrom pathlib import Path\n\nimport numpy as np\nfrom pyvisual import Plot3d\nfrom pyvisual.core.mesh3d import SphericalMesh\nfrom pyvisual.utils.data import fetch_datasets\nfrom pyvisual.utils.geometry import spacecraft_trajectory" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Load Data\n\n:func:`~pyvisual.utils.geometry.spacecraft_trajectory` queries the JPL\nHorizons ephemeris for Parker Solar Probe over a four-day window and returns\na :class:`numpy.ndarray` of shape ``(3, N)`` whose rows are\n$(r,\\,\\theta,\\,\\phi)$ in the Carrington frame, sampled at the default\n1-hour cadence.\n\n:func:`~pyvisual.utils.data.fetch_datasets` downloads (or loads from cache)\nthe CR 2282 coronal density field on the\n$1\\text{\u2013}30\\,R_\\odot$ grid and returns the path to the HDF5 file as\nthe named attribute ``cor_rho``.\n\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false }, "outputs": [], "source": [ "trajectory = spacecraft_trajectory('psp', '2024-03-27', '2024-03-31')\nrho_file = fetch_datasets(\"cor\", \"rho\").cor_rho" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Build the Faux Volume Representation\n\nThe full density grid is loaded into a\n:class:`~pyvisual.core.mesh3d.SphericalMesh`. Indexing with ``[0, ...]``\nselects the innermost radial shell at $r \\approx 1\\,R_\\odot$ as a\n2-D reference surface for the photospheric density.\n\nThe remaining shells ``[1:, ...]`` form the 3-D coronal volume. Applying\n:obj:`numpy.log` via the mesh arithmetic suite compresses the large dynamic\nrange of coronal density.\n\n:meth:`~pyvisual.core.mesh3d.SphericalMeshFilters.deconstruct` with\n``method='slices'`` converts the 3-D :class:`pyvista.RectilinearGrid` into a\ncollection of 2-D radial shell surfaces (via\n:func:`~pyvisual.core.mesh3d.build_slice_polydata`). Rendered with PyVista's\n``'sigmoid_7'`` opacity transfer function, the stacked shells map low\nlog-density regions to near-transparent and high log-density regions to\nnear-opaque, mimicking the appearance of a volumetric render without\nrequiring volume rendering hardware support.\n\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false }, "outputs": [], "source": [ "mesh = SphericalMesh(rho_file)\nradial_slice_at_photosphere = mesh[0, ...]\ndeconstructed_mesh_volume = np.log(mesh[1:, ...]).deconstruct(method='slices')" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Animate Along the Spacecraft Trajectory\n\nThe scene is assembled once and then animated by stepping the observer through\neach position in the PSP trajectory. Iterating over ``trajectory.T`` yields\none $(r,\\,\\theta,\\,\\phi)$ column per time step, which is assigned\ndirectly to :attr:`~pyvisual.core.mixins.ObserverMixin.observer_position`.\n\n:attr:`~pyvisual.core.mixins.ObserverMixin.observer_los_view` frames the\nfield of view as helioprojective angular extents\n$(x_0,\\, x_1,\\, y_0,\\, y_1)$ in degrees. Re-applying the FOV at\nevery frame ensures consistent framing as the spacecraft distance changes\nover the trajectory.\n\n

Warning

The interactive 3-D viewer is omitted here because the deconstructed\n shell mesh is prohibitively large to embed in a browser. The animation\n is also generated and cached outside the sphinx-gallery pipeline:\n sphinx-gallery natively scrapes GIF output, but the 256-color palette\n limit of the GIF format renders poorly at this scene's dynamic range, so\n the movie is written as an MP4 via a separate pre-build step and embedded\n below using a raw HTML ``

\n\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false }, "outputs": [], "source": [ "if not os.environ.get('SPHINX_GALLERY_BUILD'):\n # The following lines are included to standardize the output path for the sphinx-gallery\n # pre-processing pipeline mentioned above. These values can be omitted/altered if running\n # the script directly.\n\n output_dir = Path(os.environ.get(\"STATIC_ASSETS\", \"\")).resolve()\n movie_name = f\"p07_faux_volume_render.mp4\"\n screenshot_name = f\"p07_faux_volume_render.png\"\n\n plotter = Plot3d()\n plotter.add_axes()\n plotter.add_mesh(radial_slice_at_photosphere, show_scalar_bar=False)\n plotter.add_mesh(deconstructed_mesh_volume, opacity='sigmoid_7', show_scalar_bar=False)\n plotter.open_movie(output_dir / movie_name, framerate=10)\n for position in trajectory.T:\n plotter.observer_position = position\n plotter.observer_los_view = -50, 50, -45, 45\n plotter.write_frame()\n plotter.screenshot(output_dir / screenshot_name)\n plotter.close()" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ ".. raw:: html\n\n \n\n" ] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.13.12" } }, "nbformat": 4, "nbformat_minor": 0 }