Small Blender Things

Blender Addon: Weight paint vertices visible from the active camera

When working with particles it is often a waste of resources to distribute the particles outside the area visible from the camera. Fortunately the particle distribution can be controlled by a vertex group but weight painting the visible area by hand is a bit cumbersome. I therefore created a simple script that offers the option to paint the vertices of a mesh in the active vertex group with a weight of one if they are visible from the camera and zero otherwise. With a toggle switch you can select whether objects in the scene should be taken into account as well.

Availability and usage

All functionality of this add-on plus a lot more is now available as a convenient all-in-one add-on on BlenderMarket. It comes with an extensive PDF manual and your purchase will encourage me to develop new Blender add-ons.

The simple add-on presented in this article is available from GitHub (right click the link to download the script somewhere then install it from Blender with File -> User Preferences -> Addons -> Install from file. Don't forget to enable the check box).

Once installed it's available in weight paint mode from the Weights menu as shown below:

Simply select the mesh you want to paint, switch to weight paint mode and click Weights -> Visible Vertices. It will adjust the weights of the active vertex group and if the mesh hasn't got one, a new vertex group will be added. If you toggle the Full Scene option (in the VisibleVertices tab of the toolbar, you might need to press control-T to show it) objects in the scene might block the view as well as shown in the image below, where a cube and a sphere are shown in wireframe mode to reveal that blocked portions of the plane have been assigned a weight of zero.

The add-on was presented in this BlenderArtists thread.

Spacetree demo

Just an image I made for the Architecture Academy. Both the hedge and the chestnut tree are made with the addon, the climbing rose is made with IvyGen (showing that IvyGen and SpaceTree are friends, not competitors :-)

Credits: apart from many assets from the Architecture Academy, Blendswap proved useful too:

- rose by dansafee (the blooms but the rose bush itself was made wih IvyGen and the rose leaves are based on a scan of a roseleaf I made myself)
- wine glasses by danilius (modified to hold some wine)
- small candle by elkid (inside the blue jar)

Floor board generator, bug fix

As mentioned by Greg Zaal in the comments to this post the randomness of the floor boards increased the further you got from the origin. This was due to a faulty calculation og the center of a board.

The current version (0.0.13) fixes this and is commited to GitHub.

You can download it here (right click the link and save it to the addons directory of your Blender installation).

A new tree addon, Part VII: an all C implementation

As indicated in this BlenderArtists post I have started developing a version of the space tree addon with most of the core calculations performed by C code.

Currently most functionality is available except for apical control and pruning but a 4x speed up (approximately, your mileage may vary) is worth it. This version is at the moment only available for 64bit Windows platforms (because it was difficult enough already to get that running with Visual Studio 2012) and unlike the previous C enhancements there will be no fallback on pure Python.

Code availability

This version is developed in its own branch, 'all_c' and the installation follows the exact same pattern as for other addons (don't forget to remove any older version). The zipfile is located here. As of May 2, 2014, this is linked against the 3.4 Python library as shipped with the Blender dailt build. If you use a slightly older version of Blender you might want to use the previous commit that was linked against 3.3.

The (almost) pure Python version stays available in the master branch, the zip file for this version is located here.

Future developments

I am thinking about making a Linux version available but that's not high on my priorities. If someone is willing to compile the module however I can include it with the addon. I think it is entirely possible to have a csca.pyd and a csca.so side-by-side. Having different .so files for Linux and OSX is something else, that would require tweaking the Python imports based on the OS type.

The current speed improvements only apply to the generation of the tree skeleton. I think the same improvement should be possible for native skinning algorithm. Also, there is yet no optimization of the C code and no multithreading, so we might improve the speed even more.

Another area of interest that I am currently spending time on is creating good leaf textures. Even with a decent flatbed scanner this is not trivial, yet now that spring is in full gear in my hemisphere I have started on cherry, apple and oak leaves.

References

The space tree addon itself is introduced in a few articles on this blog and is available on GitHub. Relevant links are listed below:

A new tree addon, part VI: continuing development

The latest version (0.2.14) includes a module written in C that implements some of the most time consuming functions. The result is a 20 - 30 % speedup for the generation of the branch skeleton. For now this is only available for 64 bit windows but on a different platform the addon will fall back on pure python implementations of these functions so cross platform portability is still guaranteed.

This is a quite noticable speedup: on my machine the generation of a tree consisting of 3000 branch segments went from 3.7s to 2.7s.

Implementation notes

The C extension module was compiled with Visual Studio 2013 and seems to work fine both with the official 2.70 distribution (compiled with MSVC 2008) and with the daily builds (compiled with MSVC 2013) but will only work with 64 versions of Blender. The Visual Studion solution is part of the spacetree repository so if people are interested in porting the module to other platforms they can have a go. Detailed notes on how to compile a native Python extension with Visual Studio 2013 were published in a separate article.

Undocumented stuff

This version of the addon also contains a first try at the implementation of branch shedding.

References

The space tree addon itself is introduced in a few articles on this blog and is available on GitHub. Relevant links are listed below:

Native Python extensions for Blender with Visual Studio 2013

Researching how to create a python module in C with Microsoft Visual Studio 2013 which could be used in Blender caused me quite a few headaches so in order to spare other people the same I wrote this article that illustrates the process in a step-by-step manner. The resulting solution is available on GitHub as well.

Prerequisites

When writing native extensions for Python it is said that it is vitally important to use exactly the same compiler that was used to compiler Blender itself (or rather its embedded Python). This is especially important on Windows where even different versions of Visual Studio may break compatibility. However, I have found that Visual Studio 2013 can be used to compile an extension that is usable both for Blender version compiled with msvc2008 and msvc2013.

Currently the daily builds for Blender are built with Visual Studio 2013. This can be verified by opening Blender and generating the system information from Help -> System Info. In the generated text file (available in the text editor) the line with the Python version should read something like: ...... 1800 64 bit .... The 1800 part is the interesting bit as it identifues the version of Visual Studio, where 1800 means MSVC 2013.

The official Blendet 2.70 release for windows is still built with MSVC 2008 (the version string in the system info will show 1500) but I have found no compatibility issues, but of course your mileage may vary. It is however extremely important to match the platform: a 64 bit extension will only work for 64 bit Blender!

Writing an extension module in C

Starting point when writing an extension is this page. It's a fairly complete but lengthy introduction and its content is platform independent. To actually compile C code into a dynamic library that can be used on Windows additional information is needed. Unfortunately some information on this page is wrong or incomplete (/export:initexample is not needed, the dll needs a .pyd extension) and as there are quite a few confusing steps it might be easier to have all the steps explicitely listed for our Blender scenario.

In the following walkthrough I'll assume that Blender is installed in C:\Blender and that we'll be using MVSC 2013 express edition for Desktop. I also assume you have checked out the Python library that Blender is built with, to C:\BlenderLibraries. We need the source for these libraries for the Python.h include files. (you can checkout these libraries with any subversion client from svn.blender.org, see here for instructions. Make sure you get the 64 bit versions if you are compiling for a 64 bit platform and notice that the folder is called win64_vc12 even though we'll be using msvc 2013)

Ten easy steps

The following steps are needed to create a simple extension. each step is explained in detail below.

Create a new DLL project
Add a new x64 platform if necessary
Configure the extension to use
Configure the include directory
Configure the library directory
Add the library dependencies
Add your source code
Build the project
Copy the library to the Blender installation
Test it from Blender

Create a new DLL project

file->new project
templates->Visual C++->Win32->Win32 Project
name: BlenderTest (can be placed anywhere, leave all default settings)

In the application wizard that opens select DLL and Empty project.

Add a new x64 platform if necessary

i=If you are working on/for a 64-bit platform you'll need to add a x64 platform to your solution.

click on the configuration manager [below the menu bar in the task bar]
add a new active platform [click on the part that probably displays Win32]
select x64 and leave all the default settings

Configure the extension to use

Although a native extension is just a DLL, Python wants it to have a .pyd extension:
In the properties of the BlenderTest project
for all configurations set
Configuration properties -> General the Target extension to .pyd

Configure the include directory

The compiler needs to be able to find the Python.h include file.
for all configurations
Configuration properties -> C/C++ -> General Add 'C:\BlenderLibraries\win64_vc12\python\include\python3.3' to Additional Include directories

Configure the library directory

The Python libraries need to found as well:
for all configurations
Configuration properties -> Linker -> General Add 'C:\BlenderLibraries\win64_vc12\python\lib' to Additional Library directories

Add the library dependencies

Each configuration is dependent on a different library:
for the Debug configuration
Linker -> Input Add 'python33_d.lib' to Additional Dependencies
for the Release configuration
Linker -> Input Add 'python33.lib' to Additional Dependencies

Add your source code

in the Solution explorer, right click the Source Files folder in the BlenderTest project and slect add -> new item. Choose C++ file and give it BlenderTest.cpp as its name (although you're free to choose anything you want)

Copy the example code (you might want to use this) in the editor

build the solution (a warning about an inconsistent dll linkage of round can be ignored)

Build the project

Select the release configuration and click Build -> Build Solution

The module will be in the subfolder BlenderTest\x64\Release and be called BlenderTest.pyd

Copy the library to the Blender installation

Copy BlenderTest.pyd to somewhere where Blender can find it, for example to the site-packages directory within Blenders installation directory (e.g. C:\Blender\2.70\python\lib\site-packages)

Test it from Blender

open the python console in Blender
import BlenderTest
BlenderTest.foo()

The System console (Window -> toggle system console) should show 'Hello World'

Book review: Blender Cycles Rendering and Lighting

I was asked by Packt Publishing to review Bernardo Iraci's book and I have to say I really enjoyed it.

Pros

cookbook style with many examples
thorough coverage of all things Cycles
gentle learning curve
some really great materials (especially carpaint and food)
addresses lighting as well
plenty of relevant external references

Cons

could do with some detail renders of the individual materials
doesn't cover volume shaders

The Cycles rendering engine has been available for some time now in Blender but it is still hot because it enables the artist to produce great results. However, its many options can overwhelm a person just starting out, so Bernardo's cookbook is a blessing both for beginners as well as for more accomplished artists.

The book is well written and covers almost everything from basic node setups to very complex ones, including subsurface scattering nodes and script nodes (It doesn't cover writing shaders in the Open Shading Language, for that you might consider my book Open Shading Language for Blender). The illustrations of the node setups are also very clear and although the book's style is a cookbook, the reasoning behind the creation of the materials is often explained as well which really helps to understand why the materials are set up the way the are.

I also like that the is a fair amount of information on lighting because now matter how good your materials are, without proper lighting your render won't shine. The book presents some useful lightning setups and covers both mesh lighting and HDRI lighting quite well.

The criticisms I have are minor indeed: the book doesn't cover the new volume shaders but this is of course not a fault of the author. Cycles evolves at a rapid pace and at the time of writing volume shaders were not yet available.

Also it would have been clearer of some of the many materials presented in this book would have closeup example renders; now there is just a larger overall render of a scene at the beginning of each chapter which doesn't show the smaller details very well. Of course the sample scenes are available to the reader so you can render them yourself but it would have made for an easier read.

All in all I really enjoyed reading this book and in my opinion it is one of the better ones on Blender published so far.

Conclusion

A well written book that delivers what it promises. Well worth its money.

A critical remark to all publishers

I read the pdf version of the book and potential buyers really should consider that too because the printed version is in black-and-white.

When will publishers realize that this kind of book should be printed in color or nit at all? Monochrome paper prints simply cannot convey the information presented in colorful illustrations very well and books on rendering are all about color!

So either invest in proper color plates as the print version already is quite expensive or just stick to e-book formats.