Grasshopper

algorithmic modeling for Rhino

Hi All,

Im trying to navigate a crv around a Brep. It works well with a box brep but with a irregular (more faces on each side) box it wont include all faces and instead of going along the perimeter it will penetrate through the volume..Any thoughts?

The goal ultimately is to have a series of volumes which will be navigated through with a series of curves.

thanks

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Hello

This might help you

http://formularch.blogspot.gr/2013/06/gh-flow-around.html

cheers

alex

Hey alex!

thanks for the link. I had seen it and modified my def based on that one but it didn't work. there is something about the number of edges that a brep has which changes things i think but can't figure it out..

polyline and interpolate curve components work as expected, going from point to point and creating a curve, they don't have information about inside or outside brep, nor perimeter.

try to follow the definition from formularch and tomorrow i will try too to see if it works, that definition with your case.

cheers

alex

In the file attached originally they do have information about being inside / outside of the brep..As i said the definition by Michael has been taken into account.

still, as you see in the photo provided the white line goes around the first volume (regular brep) on the right correctly but when going to the volume on the left (irregular brep) it wraps around at first / then penetrates and lastly comes out but wraps correctly again..so it partially works..

let me know if you give it a go,

thanks mate

Well i understand you took into account Michael's definition, but copying half of the definition and expecting it to work will not give you results.

there is a reason Michael uses pull points (the component in the displace points around brep group) which you did not follow and that is why you definition does not work.

because this component pulls the inside the brep points to the breps surface so that the final curve goes around the brep and not into it.

hope this helps.

from your reply i see that either you dont understand Michaels definition or you didnt bother looking at mine..

_i did use the pull component

_the def checks for points inside brep vs outside

_based on that boolean interior points are pulled to the srf ( if it is a surface) or to the edges ( if it is a brep) by the pull component. in this case its pulled to the edges since its a polysrf. but as the pic below illustrates it works for the first and not the second..

I have some thoughts which i ll try later when theres more time

evxaristw

You are projecting only in edges and not surfaces. In pull points component you are using closest only, meaning that many points end up in the same edge. Even if you did pull your points in surfaces too, similar result would happen, because in your case i believe the closest rule does not work without having the curve going through the irregular brep. (Unless i am missing something, geometry always surprises me)

So you can try something like this

i did not put too much effort organizing the curves that form the polyline, meaning which ones of the brep perimeters will be chosen (i just listed the first item in the list).

you re welcome

the file

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yeah i tried surfaces but it didnt work. the input also needs to be a closed srf ..

still though i dont understand as the pull component seems as if its neglecting some edges based on the previous photo..maybe the points are on the same plane? 

thanks i ll have a look when i back..

Which input needs closed brep?

pull points is not neglecting any edges. it just uses those which are closest to the points so many points could end up in the same edge.

that is why i believe in your case closest condition is not suitable (if using only the edges).

Hey,

the reason i I have been saying 'neglecting edges ' is because some points seem to be closer to another edge than the one they are connecting too..

cheers

Yes i thought of that too and since you mentioned too, i figured i had to try what pull points does (closest setting) with other components to verify if pull points works ok.

it gives the same result. best thing would be to double check. if it checks must be ok and our eyes are playing games to us. If not we are dealing with a bug. But pull points, from what i can recall, has not been mentioned to be buggy.

cheers

alex

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