Grasshopper Tutorial 09 | Sweep and Loft

alright so in this video I would like to show you how to create surfaces with sweeps and with lofts and I'm going to start with the sweeps now we've got to sweep options here in grasshopper we've got the sweet one and sweep two and the difference is that sweep one has got a single rail and sweep two has got two rails now what does this rail mean here we go yeah alright so what a sweep does is it takes a section curve in this cases kind of arc and sweeps it along a rail just like a rail track so if I plug in these two curves this is the surface we get straight forward so if we do the same thing with a sweep - we now get two rails and if I plug these together we kind of get this on a barracks shape roof and the nice thing about using sweeps is that you've got exact control over the section curve and this means that wherever it will go along this surface we will have this same section so if we for example plug in a straight section which we'll do next we take another sweep too and this time I'm going to use this straight line as the section right and I'm going to use these two curves as rails and then we should get this straight curve going all across the surface and it's very useful to have control over these section curves because then you know for sure that you are going to be dealing with straight lines in this direction at the surface which might be useful in your construction I'm going to plug these two together and it doesn't work now what's going on here well what has happened is that I drew these two rail curves in opposite directions so for this one I started drawing from here to there and for this one the other direction so how do we deal with this well if we got these curves in Rhino we can select the curve and use the flip command and rhino and that will flip it in flip the direction of the curve and so now we get the surface we actually want the flip command is also available in grasshopper so if we go flip whoops flip we've got flip car so if I plug the first rail in it'll flip it back and this second input on the on the flip block is a guide curve so actually we can take the second rail as a guide for the first rail or vice versa and then it will only flip it if it's going in the wrong direction and you'll get this flag on the other side which says did it flip it or didn't it flip it so in this case it didn't flip it because they're both going the same direction so if I manually change the direction Rhino here again with a flip command nothing will change except that now that flip block has actually flipped our curve for us and flipping curves is in important and a lot of blocks where we generate surfaces so if I've got these three curves and I want to lock them a loft will try to connect these three curves with a surface and I've already got them here in a list of curves and I'm simply going to take a loft block and plug in these curves and get really weird results because one of these curves has been flipped looks like it's been the last one so I'm just going to go flip and now we've got this lofted surface now when you've got the loft block you can see that there's options and the options actually come in a separate block because there's so many of them I go loft you'll see here we've got the loft options and you can see how many there are and this is why they're kept separate so I'm going to connect them and then I'm going to discuss a few of these options but not all of them simply because this course is not about how do i generate fancy geometry in the theory or the theoretical background of geometry but some of the options are relevant to us now the first option is close should it try to close the loft now I'll see if it actually is able to do it here I don't know right now it's false it's double-click to try and true and there you go you see that is trying to create close the loop so here it goes from this curve to that curve and if I go true on the clothes it tries to close that into a single surface now the the second option is it just seems and I'll show you that in a second now the rebuild and the refit what this does is it tries to it rebuilds all the section curves you've input so that they have the same amount of control points in my opinion if you have to use these two options during your loft to create some sort for surface you're doing it wrong because you should have been thinking about how many control points do these curves have before you got to the stage of lofting and there's a general thing that we think that you should think long and hard before you start generating surfaces what that surface is going to be generated off and we'll be getting into that in future videos as well so I'm going to skip right head to the type now there's six types for the lot there's normal which is a default loose tight straight developer developer ball and uniform I'm gonna add a slider here and go through them so by default it's on zero and this is what you get now if I go to one which is loose you can see what happens it doesn't take those section curves and their control points to serious anymore it kind of takes a Mazen as a suggestion as to where the surfers are supposed to go along and if we go too tight it slave Ashley goes through these curves so if I bake this surface you will see that it goes exactly through those curves now the third option is straight and here now previously we had when it came to this curve it tried to create a continuous smooth surface through this curve if we go to straight it'll try to create a straight line from one curve to the next and then stop and then go for the next one now this can be useful some loft things and the next one is developable now developable means that it tries to create a surface or a set of surfaces which can be represented as a plane so imagine you take a piece of paper or piece of sheet metal and you bend it into some shape and the end that shape will always be developable because you can always return it to it's flat original state now here's trying to do the other thing is taking a bent or curved surface and tries to divide it into sub surfaces which can be developed and if you simply plug this in you'll often get pretty ugly surfaces like this one where you've got lots of surfaces meeting in one point and this is because there's very strict rules as to which geometries can be developed and I'm going to give you an example so I'm going to copy this reoccur and I'm going to now take these two curves and tell it to create set multiple curves here we go so now we're just lofting between these two same curves and even though we're now on the on the developable option you can see we get a clean surface no additional seam lines or anything and we'll always get this as long as we keep the same curve at both sides as soon as I go here and turn on control points and change this you'll start to see that we get these little sections at that side where it can't create a single developable surface from these two curves so this is another example where it's important to think about what is my input geometry and what kind of surfaces am I going to try to create from this alright to talk about the last option of the lofts which was this adjust theme seems this becomes relevant once you've got closed curves you might see two circles but for Rhino these are curves these are two curves and they have a start and end point you can't see it right now but you'll see it in a second so I've got these two circles and I'm now going to loft them so I get a cylinder I'm going to get myself the loft options again loft options now what I'm going to do is if you look at this line here this is the seam line so this is where the two circles start and end all right so they start go once around an end here and so the surface that gets created also starts along this seam line so it tries to match the two the joints of the curves and then creates the edge of the surface around because all these NURBS serves is everything you see here underneath it's all square surfaces that have been bent out of shape and then maybe trimmed around the edges so if I take this top circle and start rotating it you'll get this constricted shape because now it's creating a connection between the the seam joint here and here and then this is moved around the circle to create this shape now if I go to the just seams and it's currently set to false if I now take a toggle and set it to true it'll move one of those seams underneath the other one so that we then get a cylinder again now what all this shows is that you need to be careful when you're creating surfaces be it in Rhino or grasshopper you need to be careful about which direction your curves go you might have to flip them and you can't turn any surface into a developed surface you need to think beforehand if you want to develop the surface what kind of curves cannot connect to each other what kind of shapes can I connect to each other to create geometries that later work for me all right thank you for watching

Channel: Individualized Production in Architecture

Views: 24,582

Rating: 4.9115043 out of 5

Keywords: Grasshopper, RWTH

Id: rzxQy_TXGlk

Length: 13min 3sec (783 seconds)

Published: Thu Nov 17 2016