BIM/Arch development news articles from Yorik's blog

[joancabeza]

I also worked further on the GBXML exporter itself, but met a temporary showstopper. To test GBXML output, we need an application that can import GBXML and, preferably, do something with it. As far as I know, the only one avaialble that is open-source and runs on Linux is OpenStudio, which by the way seems a really nice thing. It is a bit hard to find the source code of OpenStudio, but it is on github. Problem: OpenStudio uses libraries about 2 years old (boost mainly) and doesn't run on modern Linux systems (their officially supported platform is an Ubuntu from 2012...) So I'm now busy trying to make OpenStudio work on my machine, which requires a ton of small fixes and is not a very easy task for a C++ ignorant. We could of course ask for help to the OpenStudio people, but the project has 691 open issues, I don't think we have a lot of chances to be heard.

I'm writing because I've just installed OpenStudio easily on LinuxMint 18.3 (Mate 64). It seems that in short period you would be able to make the Energy Certicate (that it's mandatory for every new building in Spain) with it. The actual program is one of the ugliest thing i've had to work with...and professionals are waiting for something that would replace it.
I'ts seems that you can import IFC to OpenStudio but it also has a plugin for Sketchup which makes the workflow really easy. Do you thing it would be difficult to do a similar thing with FC? That would mean that you could be working with your model in FC an make energy simultions while you are defining the project.

[yorik]

What I gathered so far:

- energyplus seems the only realistic option to generate energy analysis the open source way. It is a command-line application, which takes input text files and produces output text files. So technically it is totally possible to use and embed it within FreeCAD.

- energyplus uses the same concepts as GBXML: your building must be made of "zones" or "compartments" or "spaces" with no gap between them (the sum of all spaces volumes = the total volume). Each space has "boundaries" (walls, floors, ceilings) which can be exterior or shared with another space. These boundaries can also have openings (windows).

So I think there would be several things needed to produce energy analyses from FreeCAD. Many of them would be needed the same way if using GBXML or energyplus directly:

- Allow to make such a model, or, better said, extract such a model from a "classical" BIM model. Spaces are already there, so you can build all the spaces of a project, but at the moment there is no way to derive boundaries and window information. I am not really sure how to do that yet.

Then exporting to GNXML shouldn't be too hard. Supporting energyplus, however, would require an additional huge step, which is parsing the output data from it, and do something useful with it...

[damian]

Hello @joancabeza and @yorik
The next months I'll publish my custom workbench. There you could:
1º) Import to FreeCAD the IDD schema of energyplus and openstudio, whatever version
2º) draw a complete building with a ''no thickness model'' and customize the properties of all objects created following the IDD schema imported
3º) import/export energyplus and openstudio files
4º) make simulation with energyplus
5º) export to DOE2
6º) ...

[damian]

Problem: OpenStudio uses libraries about 2 years old (boost mainly) and doesn't run on modern Linux systems

To compile OpenStudio, especially its python binding, is a headache. The last version of openstudio can be easilly installed in ubuntu 16.04, and include the last Radiance. But try to compile is a kamikaze mission, at least for me.

It seems that in short period you would be able to make the Energy Certicate (that it's mandatory for every new building in Spain) with it.

The official program uses a DOE2 derivated, and its draw application is terrible.

[damian]

a plugin for Sketchup

FreeCAD must be clever of a clean implementation in all steps, draw, process and postprocess ...

- Allow to make such a model, or, better said, extract such a model from a "classical" BIM model. Spaces are already there, so you can build all the spaces of a project, but at the moment there is no way to derive boundaries and window information. I am not really sure how to do that yet.

To my understanding, the hard task actually is to define the spaces or zones in an agile way. The information of the boundaries could be extracted by contacts between spaces and walls, a little bit expensive due to the boolean operations but simple and effective.
In all case, I design a complete set of tools in order to draw buildings from simple sketchs and obtaining polygonal surfaces, which carry with the related IDD model (openstudio and energyplus), and in consequence, could be edited, simulated and imported/exported.
In a second stage I facility the conversion to Arch Workbench, and with improvements in the space tools (perhaps volume maker), conversion from the Arch Workbench. Of course, it also is possible directs exporters from BIM to openstudio (with or without greenbuilding and/or ifc).

[joancabeza]

Wow! This workbench of yours looks great. I'll really look into it. Cheer on your work!

[yorik]

To my understanding, the hard task actually is to define the spaces or zones in an agile way. The information of the boundaries could be extracted by contacts between spaces and walls, a little bit expensive due to the boolean operations but simple and effective.
In all case, I design a complete set of tools in order to draw buildings from simple sketchs and obtaining polygonal surfaces, which carry with the related IDD model (openstudio and energyplus), and in consequence, could be edited, simulated and imported/exported.
In a second stage I facility the conversion to Arch Workbench, and with improvements in the space tools (perhaps volume maker), conversion from the Arch Workbench. Of course, it also is possible directs exporters from BIM to openstudio (with or without greenbuilding and/or ifc).

This is not so simple because boundaries between two spaces should be right in the middle of a wall. So it is pretty hard to find that wall in an automatic way. Somehow, basically I believe there should be a relationship table between all the faces of a space and "physical" objects (walls, slabs, etc...). Then, all the needed boundary information could be obtained easily (materials, openings, etc...).

I have no clear idea yet how that relationship table could/should be built, and if it should be built automatically,etc. There is also the same issue as always: Topo naming (the faces number can change). But there could be a number of interesting things to do to help, such as give different face colors to spaces when a face has a bound object, etc...

I am personally not a fan of building "weightless" models first and then turn them into BIM models, I prefer the contrary, but I understand this is a question of choice and many people want the first method. Ideally this should work both ways. That's where that "relationship table" is interesting, it is basically bidirectional...

[damian]

This is not so simple

yes

[damian]

Somehow, basically I believe there should be a relationship table between all the faces of a space and "physical" objects (walls, slabs, etc...). Then, all the needed boundary information could be obtained easily (materials, openings, etc...).

This is fundamental.
Every Space must have a clear list of all "physical" objects (walls, slabs, etc...) which form its volume. And this volume initially is an interior volume, that is to say, formed by determined object's surface. Later on, come the 'gap' problem.

because boundaries between two spaces should be right in the middle of a wall

The boundaries must be right in de the middle, y one side of the wall, or in another side of the wall, at user demand. In consequence, the space volume must be rectified, and finally obtained the surface with its vertexes. This is very endeavouring objective.
The bi-directional conversion is plenty of challenge, in the two directions. For this reason, I'm always searching for new tools and features.

[damian]

Another relationship table is between E+ objects and FreeCAD objects. For instance, a FreeCAD Wall corresponds to a E+ BuildingSurface:Detailed, and vice-versa.
And E+ IDD schema could have one thousand different objects. A nice start point for FreeCAD could be a table with one or two dozen objects, which allow making a few examples.