adds blender script example

Author: danielpeter

utils/Visualization/Blender/README.md

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+# Blender visualization
+
+
+Blender is an open source, cross platform suite of tools for 3D graphics creation
+https://www.blender.org/
+
+
+Examples:
+- bin_sphere/      - a simple blender file with a textured sphere
+
+- python_blender/  - python script example to create a blender scene, with a textured sphere, lights and camera objects
+
+
+

utils/Visualization/Blender/python_blender/README.md

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+# Blender scripting example
+
+Blender for 3D graphics creation<br>
+https://www.blender.org/
+
+
+## Installation
+
+The python script `blender_sphere.py` uses Blender's python module. To use the script, we also need some interpolation routines from  matplotlib/scipy which are not provided in the default python version that blender internally uses. One possibility to use the systems python frameworks is to set an environment variable `BLENDER_SYSTEM_PATH`. For example, on Mac having python installed through [MacPorts](https://www.macports.org), one can set
+```
+export BLENDER_SYSTEM_PYTHON='/opt/local/Library/Frameworks/Python.framework/Versions/3.10/'
+```
+For this to work, the python version must match the internal python version from Blender. In this example, Blender version 3.4.1 uses a python version 3.10.
+
+
+## Simulation setup
+
+First, run a (global) simulation example, e.g., in `EXAMPLES/global_small/`, turn on the surface movie flag in the `DATA/Par_file` and set the output type to velocities:
+   ```
+   MOVIE_SURFACE                   = .true.
+   ..
+   MOVIE_VOLUME_TYPE               = 6
+   ```
+
+   This will create a series of `moviedata***` files in the example `OUTPUT_FILES/` folder.
+   Create a (symbolic) link to `OUTPUT_FILES` into this rendering working directory, e.g.,
+   ```
+   ln -s ../../../../EXAMPLES/global_small/OUTPUT_FILES/
+   ```
+
+
+## Visualization
+
+To plot an image with python's matplotlib module of such a `moviedata***` file, you can type:
+```
+./plot_moviedata.py --moviedata=OUTPUT_FILES/moviedata002800 --show
+```
+This script just uses the default python framework with matplotlib/scipy to interpolate and plot an image, without any need of blender's functionality. For more options on this script type `./plot_moviedata.py --help` . It is meant to check and quickly visualize the moviedata files.
+
+
+### Blender textures
+
+For the example here to work, the blender script `plot_blender_sphere.py` will need a few texture images for the rendering of the sphere (earth image, topography, clouds, night). These can be created and put into the `resources/` folder. These textures are not provided here, as the file sizes can become quite large for high-res images and would bloat up the github repository.
+
+The `shakemovie` repository uses textures as well, you can use the script `convert_tga_to_jpg.sh` in the `resources/` folder to convert those `*.ppm` and `*.tga` files to high-res JPEG and PNG files, which are formats readable by blender.
+
+You could run the script also with no textures by setting the texture paths to empty strings in the user parameter section in file `plot_blender_sphere.py`.
+
+
+### Blender rendering
+
+Once the texture files are created, you can set the corresponding file names as user parameters in the python script `plot_blender_sphere.py`, then type:
+ ```
+ ./plot_blender_sphere.py --moviedata=OUTPUT_FILES/moviedata002800
+ ```
+
+ This will create an image `out.moviedata002800.jpg`. For more script options, you can type `./plot_blender_sphere.py --help` .
+
+
+Finally, to create an animation, you would call the script with multiple moviedata files as input. It will render all data and rotate the sphere to create a movie:
+ ```
+ ./plot_blender_sphere.py --moviedata=OUTPUT_FILES/moviedata00**
+ ```
+
+Please be patient, the rendering for many moviedata files can take a while. The movie file is stored as `out.anim.mp4`.
+
+
+Feel free to modify and contribute any improvements to these python scripts - and have fun with blender for scientific visualization!