Problem with wind velocity vector results- All vectors appear as blue!


Hi everyone,
It’s a while that I have this kind of problem with BF results. As you see in the attached image all vectors appear as blue. I also conducted another test in which i put the test point surface somewhere that it did not have any intersection with the building geometry and it all gets correct. all coloured vectors appear.
I guess it may be a problem with my building geometry ( it is a closed polysurface).
any idea?!


hi @samira
It’s hard to tell without looking at your definition. Please share it and confirm that your rhino units were in meters.


Hi @OlivierDambron
Thankyou for your attention.
Here I put the definitions & yes the units is meters in all files.
1-Case1-1–test (71.1 KB)
3-Case1-2–test (75.3 KB)


Hi @samira

First I notice that your file contains old butterfly components. please make sure to have them updated and replaced.

Let us know how it goes.


This is how you can update butterfly to the latest version


@OlivierDambron thanks alot to you. I updated butterfly succefully and with special thanks to @devang for the great instruction on updating it. It really helped me. Now Much of my problem with vectors is solved although still i have that problem with some of the horizontal analysis surfaces but i’ll try to fix it.
Now I have a new concern. Do you know if I can somehow get the drag coefficient of the building as a number from BF? I tried to find something relevant in previous discussions & all I get is that I think It’s kind of related to function object. Am I right? And How?!


Hi everyone.
Could you please answer me on this? I could use any advice from you


Hi @samira

You can calculate drag coefficients with an OF function object. It’s not yet developed in BF however, but you can find all the objects here (for example):

I haven’t tried it myself yet so can’t help much at the moment. You can try and searching in the OF tutorials, you can also find those online, can look for drag in the github.

Kind regards,


Hi @TheodorosGalanos
Thank you for your advice. I actually don’t know much about scripting but i just tried to figure out something from what i read in OF & BF documentations. Now I gave :point_down: as the input of function objects component & everything seems to be ok. (Does this script seem reasonable to you?)
And It may be a silly question but i don’t know where to find the outputs( lift & drag quantities). I’ll appreciate any help from you.

type forceCoeffs;
libs ("");
log yes;
writeTofile yes;
patches (walls);
liftDir (0 1 0);
dragDir (-1 0 0);
pitchAxis (0 0 1);
magUInf 100;
lRef 3.5;
Aref 2.2;


Looks good to me, one way to find out :slight_smile :slight_smile: Make sure the ‘walls’ is the actual name of the butterfly geometry or geometries you wish to calculate drag for.

The results should be saved in a postProcessing folder inside your case folder.

Kind regards,