Introduction

The SVGWriter package provides a set of Python script files for authoring SVG documents with Blender and Freestyle. SVG documents to be generated are either still images or animation clips.

The latest version of the SVGWriter package is available at:

../svgwriter_b26.zip

Blender 2.67 is required to use the SVGWriter package. The package has been tested with a 64-bit Windows build of Blender trunk revision 56331.

The SVGWriter package includes the following files:

• svgwriter_image.py

  A style module for Freestyle to generate a single still SVG image from a 3D scene in Blender.

• svgwriter_anim.py

  A style module for Freestyle to generate a series of still frames comprising an SVG animation clip.

• svgwriter_concat.py

  An extension file for Blender 2.6 to provide a graphical user interface for postprocessing a set of frames.

The first 2 scripts can be stored in an arbitrary directory, e.g. in $BLENDER_DIR/2.67/scripts/freestyle/style_modules/, where $BLENDER_DIR refers to the top directory of a Blender installation. The last script needs to be put into $BLENDER_DIR/2.67/scripts/startup/.

Still image rendering

Follow the steps below to render a still image from a 3D scene in Blender:

1. Enable Freestyle in the Freestyle tab in the Render buttons.
2. Open svgwriter_image.py in the Text Editor window.
3. In the Freestyle tab in the Render Layers buttons, select the Python Script Mode from the Control Mode pull-down menu, and add svgwriter_image.py into the style module stack.
4. Go back to the Render buttons, and specify image resolutions in the Dimension tab and an output directory in the Output tab.
5. Start still image rendering, e.g. by selecting Render >> Render Image (F12) from the menu in the Info window.

After the rendering has finished, an SVG file named output.svg is created in the output directory.

Since Freestyle is a programmable line drawing framework, you have a considerable amount of freedom in defining new style modules yourself. At the end of svgwriter_image.py, you may find a list of stroke shaders like below:

shaders_list = [
        #ConstantThicknessShader(2),
        pyDepthDiscontinuityThicknessShader(1, 4),
        ConstantColorShader(0, 0, 0),
        #pyMaterialColorShader(0.5),
        writer,
]

You can enable/disable a shader by removing/adding # in front of the shader name. You can also control line thickness and line color by changing the shader parameters using a text editor. The "writer" in the above list of shaders is a shader to generate the SVG still image. Since shaders are executed one after another in the order in the list, you need to specify the SVG writer at the end of the shader list.

Animation rendering

Follow the steps below to render an SVG animation clip from a 3D scene in Blender:

1. Enable Freestyle in the Freestyle tab in the Render buttons.
2. Open svgwriter_anim.py in the Text Editor window.
3. In the Freestyle tab in the Render Layers buttons, select the Python Script Mode from the Control Mode pull-down menu, and add svgwriter_anim.py into the style module stack.
4. Go back to the Render buttons, and specify image resolutions, frame range, frame rate in the Dimension tab and an output directory in the Output tab.
5. Start animation rendering, e.g. by selecting Render >> Render Animation (Ctrl F12) from the menu in the Info window.
6. After the rendering has done, choose a horizon color (in the World tab in the World buttons). The horizon color will be the background color of the animation clip.
7. Go to the SVGWriter tab in the Render buttons, specify an output SVG file name, and press the Concatenate Frames button. This results in an SVG animation clip file stored in the output directory.

When the rendering in Step 3 has completed, a series of XML files in a file name like frame000001.xml are created in the output directory. Each XML file contains an SVG fragment that draws a still frame comprising the animation clip. The controls in the SVGWriter tab (provided by svgwriter_concat.py) allow you to concatenate these SVG fragment files into a finished, single SVG animation clip file.

You can change stroke shaders and their parameters by manually editing svgwriter_anim.py as in the case of still image rendering.

Known issues

• Only constant line thickness and constant line colors are supported due to the fact that Freestyle strokes are translated into open SVG paths. Use of variable line thickness/color shaders will lead to unexpected results.

License

This is free software; you can freely redistribute it and/or modify it under the terms of the GNU General Public License (version 2 or later).

This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY. Use it at your own risk.

Contact

Tamito KAJIYAMA <rd6t-kjym at asahi-net dot or dot jp>

Please, feel free to write to me in case you have comments, suggestions, and/or patches. Both English and Japanese are welcome.