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Return to Rhino3d - Modelling in Rhino - Generating Production Surfaces and Solids from 2D Intent - Video
Hi this is Phil from Simply Rhino. This is the second video in the tutorial looking at creating production quality surfaces from 2D design intent.
The starting point for this exercise is a series of 2D drawings presented in Adobe Illustrator and we’ll look at quickly construction some of the major construction curves in Rhino before producing a series of surfaces from the minimum of curve input. The emphasis is on creating high quality surfaces relatively quickly, before arriving at the final 3D solid model. This tutorial is in three parts and this is part two.
So having created the body and the handle, the next task is to model the spout. Now the spout is fairly well defined here in terms of its boundary curves, but it’s likely that we’ll have to do a little bit of investigation or experimentation to see how the bottom of the spout transitions. It looks here as though we go from something that’s fairly sharp to something that blends out to a wider overall blend at the bottom of the spout and you can see there’s quite a bit of sharpness here at the front of the spout.
So let’s first of all turn on the side elevation and go to the left view and then let’s open up our new 2D curves layer, and we’ll call this spout curves, change the layer colour of this and make this active. And I’m going to lock my side elevation here. I’m just going to trace off some curves here, again using the interpolated curve command. So again I’m just picking in as few places as possible here so I can get this shape about right and I’m going to extend both of these curves, again using the bi-arc option. With both of these curves, I want to make them slightly over long, particularly this top one. Okay, what I want to have here are two curves which are going to have a good relationship to each other, so that if I choose to use a sweep or possibly a loft here, that the curves roughly have a perpendicular relationship to one another, so that my surface builds in a nice uniform way. To help me do this, I’m going to create an average of these two curves in the centre. But before I do that, I’m just going to rebuild each one of these curves to degree three, four control points. I’m just going to have a look here – we’re a little bit away from the intent here but because the bottom of the spout is the area that I’m going to probably be iterating a little bit, I’m not too concerned about that at the moment.
So I’m going to create a mid-curve between these using the between curves command and pick the start and the end curve and I just want one here, and then the reason for doing this is so that I can create a perpendicular line from here using the both sides option, which will give me something that I can trim the top and bottom curves with. As I say, I want to maintain this perpendicular relationship. So just trim these away now, and now we’ve got a better relationship between these two curves.
So these will be on the centre line of my geometry, I’ve had the project on, and the next curve I need to establish is going to be roughly midway between these two curves. These are the tangent curves and if I go roughly midway between these, it should give me a curve in approximately the right position. So I’m going to use an offset curve here and I’m going to use the through point option and just find roughly the midpoint here. Then I’m just going to check how many points this has, again it needs rebuilding and we should see that this will need a little bit of extending here again just to make this the same length or have the same relationship as the other curves. So I’ll rebuild this again because I’ve extended it and then this curve, I can position in its 3D position, and I can do this by opening up the plan view and going to plan and turning on the control points and moving this curve over. Okay, as well as moving of course, I can use the nudge keys here which is ALT plus the arrows to do this and this is probably a bit easier to use ALT plus the arrows here. Now it’s going to take a little while to get this right. I want to keep these points in their position along the global y axis here. Again, it will just give me more options when I want to create a better surface. Okay so that looks reasonably okay and if we go back to our left view here, we’ll see that curve is in its same position in our left view.
So now I can mirror that curve with the copy option on and mirror this along the global y axis. So we now have some curves that we can start to build the spout from.
So next we can start to build some spout surfaces. So I’m going to create a new layer here on my surface layers and call this spout surface outer. I’m going to make this active. I’m going to turn off the elevations in place and make sure my project is off, and go to a perspective view. So the aim of this exercise is that we’re using a minimum amount of curves to define surfaces here. So I can use the top three curves here to define the top of the spout, and the two outer top curves and this curve here to define the lower half of the spout, and I’m going to initially use loft here to create these curves. So I’m using a normal loft which is an interpolated loft and I’m using the do not simplify option, which gives me a nice clean surface. And I’m going to build two lofts here that will give me my spout shape.
Now the main thing about this, is this spout here is not sharp enough. If you remember when we talked about the shape earlier on, we want to have a tighter if you like, radius at the bottom of the spout here that transitions to something that’s a little more blended at the bottom. So this is fairly easy to fix and we’ve got a way that we can do this reasonably interactively. But before we do that, I just want to check on the bottom shape of the spout. So I’m going to very quickly turn on my outer surface and I’m just going to generate an intersection curve. So curve from objects, and intersection and then just turn the body surface outwards. I’m then going to go back and I’m going to turn on the spout elevation and just hide that surface. I just want to see how my inter-section – I just want to see how that matches with what is on the CAD. It’s not quite there but it’s not too bad. So that’s just a quick way of checking my surfaces against the elevations.
So turn everything back on again and what I really want to do now is to look at sharpening up this front edge and there’s a reasonably nice way that we can do this. I’m going to turn off my curves here and get rid of this inter-section curve. So first of all, what I’m going to do is split this lower surface at its midpoint here which is marked out by this isocurve. So I’m going to use split isocurve and I’m going to make sure that the shrink option is enabled. That gives me an untrimmed surface when I split with an isocurve.
So next up I’m going to look at creating a surface here that we can use to actually create a shape change in this front. So if we look at the two halves of the spout together, we’re effectively going to put a crease in the front of the spout to sharpen up this end. So to do this, I’m going to just create a line, let’s say of a nominal length, let’s say 20 millimetres long and then I’m going to go to transform and orient, and perpendicular to curve and I’m going to orient this so that it’s perpendicular to this edge. I’m going to have the copy option on and I’m going to put that line at each end of the surface edge. Then I’m going to set C-Plane that’s perpendicular to the edge, so use C-Plane, perpendicular to curve and I’m going to take this object and I’m going to rotate it. I’m going to rotate it through something like 25 degrees here, then set my C-Plane back to where it was previously. So the idea here is, I’m going to create a dummy surface or a sacrificial surface which I’m only really going to use to match too. So I’m going to create a sweep 1 rail here and I’m going to sweep using that surface edge as a rail and these two curves as cross-sections. Now obviously this cross-section here at the bottom is perpendicular to the rail, this is 25 degrees out of perpendicular. So in other words, my surface will be tangent at the bottom here, 25 degrees out of tangent at the top. To help this along, I’m going to use the align with surface option here as well. This wants to give me a surface that has aligned tangent where possible here. Now of course, here it’s going to pull this out of tangent.
So this surface, we’re not using to actually build with. We’re really using this just as a means to an end to match to. So if I take this surface now and match it to this and create a tangent match, it shouldn’t change the shape at the bottom but should change it at the top. So I’m going to go to surface, surface edit tools and match and pick the surface that I want to change and the surface that I want to match to. And I want to match for tangency and I’m not too worried about the other end of the surface. I don’t want to average the surface of course; I don’t need to refine the match. Refining the match here will add more points to the surface. This is not what we want to do in this case, and I can okay that. Okay, now if I just delete that surface and these curves, and now mirror the spout, what we should see here now is that the bottom is still going to be tangent and we should see a crease that gradually washes out.
Now of course I don’t really need the sharp crease here, I want this to be softened, and if I was to join these two surfaces together and use either a fillet edge or a blend edge along here, let’s say with a radius of about 3 millimetres and I chose the distance between rails here, this would most likely fail where we ran out of room along here. I should be able to get a roll and all fillet to propagate. But in either case, using the solid fillet or blend tool here, will give me a three sided surface, which basically runs to a point down here where we achieve almost no shape change at the bottom of the spout. You can see that the width of this isn’t particularly controllable and also that three sided surface is slightly problematic. This part of the shape here might look right, but certainly down here, this isn’t the geometry we want.
Now, we’re going to take a look at this with the environment map on, just to see if this actually looks sharp enough at the top. That looks not bad for what I wanted there. So you can see that there’s a good definition there about that edge. So what I’m going to do is to just duplicate the edge of that blend just there, and then I’m going to copy that just to the clipboard and I’m going to undo a few steps here to go back to my surfaces. Then paste in that curve and I’m going to just separate these two surfaces. I only need to work with one of these, and I’m going to try again splitting with an isocurve and I’m going to snap on to that end of that curve, and I’m going to do that again, making sure that I have the shrink option on and then remove this and mirror the spout again. Then I’m going to create a curvature continuous blend using blend surface between the two edges. So I’ll go for G2 and I’ll preview this. Of course, I can make this blend slightly sharper or less sharp using this tool. Let’s leave it about there, that looks good.
Okay, because the blend tool is blending in a curvature continuous way, we should see that in real terms we’ve still not changed the surface much down here but we’ve put in this slightly more defined crease in to the top – not crease, slightly sharper radius that blends out. So you can see that there. You can see how that is sharpish there and then blending out. That looks quite good so I’m going to join this back together again.
Before I do too much on these surfaces, it’s probably a good idea to offset them. Now the general offset of the body is 3 millimetres but I’m going to go for a little less on the spout, and rather than do this as a solid or a shelling operation, I’m going to create separate surfaces here. This just gives me a little bit more scope later on. So I’m creating a new surface. I’m going to call this spout surface inner and I’m going to take a look at offsetting this lower half of the spout. So I’m going to use offset surface here, and one of the things that’s likely to happen here is that because this blended area here is quite small, it’s quite possible that this may deform and these two side surfaces may cross over themselves when we offset this. So let’s just take a look. I’m going to use a distance of 2.5 millimetres here rather than 3 millimetres, just to keep the spout slightly thinner and let’s just ran that command, and you can see here that this has really mangled the blend here. The offset here has not worked correctly. So we may be better in this instance, just exploding this front part here and offsetting these individually like this, and then if I just hide these front surfaces here, you’ll see I should have room now to just create the blend here manually, and just manually create this part of the B-Surface. Check that it joins together and we should see here that even though this is a B-Surface, we can get a very nice, reasonable surface here that looks pretty nice and smooth. So I’ll offset this other part of the surface and show in the other parts. Then I need to look at containing the top and the bottom so I can trim everything up.
So I’ll go to my left view, I’ll re-enable the side elevation. I’ll go to a wire frame view and then I can see this angle at which this is cut back here so I’m just going to draw a line here. Just use the TAB key here to snap the direction and I can use that line to trim away the various parts here. Okay, and then I’ll just neaten up this lower edge as well so I can do the same there, just turn on the elevation again. I just want to make sure that I don’t come too far inside here. So let’s go here and trim this out. Okay, so let’s go now to the outer surface and take a look at this and join it together and go to the inner surface and just trim this up here. So I’m going to just generate an inter-section and trim with that inter-section, if I can pick the right object. There we go, and then join this together. Select any curves and delete them. Turn on the spout here and then, whether I do this now or whether I do it later, I can just cap off this front face here. Let’s do that now. It may be that I have to remove that later. So I think what I’ll do is I’ll create the front face. I’m going to use planer curves and I can just pick all those curves on that edge, that just creates a planer curve there. Now later on we’re going to need to run a fillet down the inside edge and the outside edge here of the spout and then run a fillet around here.
Now for now, what I’m going to do is put that end surface on the outer spout surface layer and I’m not going to join all this together as yet. It might be better to join this to the body first of all. So let’s just have a look at what we’ve got now. We should have body and handle now. Okay, important thing to check now before we go too far is that our inner surface here of the spout, is clearly intersecting with the inner surface of the body, which it is.
So now that we have these components created, the next step is to create the top surface and the bottom surface and then I can start to join the individual parts of the pot together. So I’m going to turn all the surfaces off apart from the outer body surface. I’m going to turn on the side elevation in place and then set my view to the left view and move to a wire frame view.
Now the surface that creates the top of the lid, is also going to be the same surface that creates this top portion of the pot, so in other words, I can create one large base surface and use this to fulfil both roles. So I’ve created a new layer here called top curves and first of all, I’m just interested in where this intersection point between this curve here and the side of the object is. So I’m just going to draw an interpolated curve here, just tracing over the top of this curve here, and I’m going to extend this using the bi-arc option and I’ll just run that until I get that intersection there and that intersection point is where my theoretical intersection or the sharp edge is.
Now I could trace off a curve along here, but there is a couple of things I want to do here. I want really to have slightly more curvature in this surface or curve than I’ve got here and I’m going to start this on the centre line, and rather than drawing an interpolated curve, another process I could use here is to take a straight line because I know where the start and the end of the curve is. I can rebuild this to this exercise, degree three with a point count of four, and then turn on the control points and this control point here, I need to set at the same height as this point here, so that I can just set this in Z. Snap to there. And then this point here, I can just move upwards.
Now it may help here to have the curvature graph on because it’s probably quite easy to get a bit of an S shape going on in this curve here, so I’ll go to analyse, curve, curvature graph on and we’ll analyse this shape and that’s where we can see here, we’re getting this negative curvature here. So I’m going to take this point here and move it along and you’ll see as I’m moving this along how this shape changes. It’s probably not too bad where it was there but this point here needs a little bit of work. Rather than using move, let’s use the nudge keys and just push this point up and you’ll see as I push this point up here, the curve starts to get all positive. Now then, I can move this point along and maybe push this one down slightly and get something that looks a bit better. What I want is a curve that just gradually gets a little tighter as it gets to the top. Something like that looks quite good.
Okay, now where this meets the surface here, this surface, because of the way that we built it is elliptical as we take cross-sections through it. So if I take an isocurve from here, snap to that point there, then this should be a nice pure curve, as you can see here when I turn the points on. So I can use as I have done before, a rail revolve here to build this top surface. So I’ll create a new layer and call this top surface outer and make it active. Turn off the elevation in place, turn off the body surface outer and just reset my C-Plane here and do a rail revolve. So profile, rail and describe the axis, and that’s the resulting surface. Turn on the body surface and I just want to check this, for example against the handle elevation. Okay, again you see we’ve just got that slightly bit more curvature to it which is what I want. That looks good.
Okay so that’s the main surface for the top. So I can duplicate this layer and object and just change the name of this. This is going to be my lid surface and I can also offset this as well to give me the main inner surface of the lid and the inner surface of the top of the pot and for this I’ll just use an ordinary offset and the distance I want is 3, so I’ll offset to a reasonably good tolerance this time. I’ll keep this at the absolute modelling tolerances, and flip the direction and that’s my inner surface. So I’ll put this on the new layer and again, duplicate layer and objects and this will be my inner surface of the lid as well.
So we can probably add the local detail in to the top surface of the pot before we actually join it on to the rest of the pot. So I’m going to go back to the top surface outer and go to my top view here and turn on the plan for my elevations in place and I’m just going to check and unlock the plan. I’m just going to check here that’s the aperture in the top surface and there’s a recess about here. So let’s have a look at the section and you can see that we’ve got a recess here. Now on the side section, this recess will change locally. So what we can actually model here, now, is just a general recess and then cut this D-shape out of it. That’s essentially what we’ve got here. So we can do this in a number of ways and probably because we’ve got a section here, we can use rail revolve to help us out with this. So all I need to do here is to draw this portion here and I’ll draw it without the radii. So we’ll draw a line here. This can be overlong, and here and this doesn’t need to go all the way to the middle but it wants to be just slightly longer than this portion here. Then I can turn all this information off here and I can just connect these two curves. So I use the connect command here, it just joins those together. So go back to perspective, switch to wire frame, just for a moment, and I’ll offset it by my thickness which is 3 and I’m going to build the inner and outer recess at the same time for the pot.
So surface, rail revolve, that’s the profile. That’s the rail. That’s the start of the axis and that’s the end and then we’ll repeat this. I’ve built this on the wrong layer so that should be on top surface outer and then let’s make top surface inner the active layer now and repeat the rail revolve with the bigger curve.
Okay so there we go, so that’s what we’ve created there. So if we go to top surface outer now, just turn off our curves and these two can be trimmed with each other. I generally like to just create an intersection curve here and trim with the intersection curve and then do the same with the top surface inner and then we can look to that D-shape. So go back to my plan view, turn on the plan view and that is the cut out. Now let’s just have a look what the geometry is like for that. We can’t use those curves, they’re not good enough. So just for a moment let’s copy that curve on to our top curves layer. We’re just going to use that as a reference. So there it is.
Now again, this should be elliptical so if I find an intersection here, if I can find one. It’s actually finding an end point, there’s the intersection of that point there, and I mirror that point around the origin and then I’ll just draw a quick guide curve out here, or line rather and find an intersection of that and then mirror this.
Okay so I’ve now got the four points I can draw an ellipse through. So these curves can go and I’ll just turn on my top curves layer here and I’m going to draw an ellipse now. I’ve turned on project just to make sure that I snap correctly here and do an ellipse from centre. Centre of the ellipse will be at 0 and then snap to one of the points here for the major axis, and another point for the minor axis. Then draw a line from both sides from where the D-shape is, just turn off the surfaces, delete the reference curve and then trim these off with each other.
Okay so that’s the shape of my D created with some nice clean curves. Turn on the top surface outer, just push that curve upwards and turn on top surface inner, just push that curve up slightly more and we’ll just extrude this straight and then we can trim this out. So trim the top of this with the top surface, so I’ll create an intersection curve again. Let’s turn the curves off to make things less confusing and repeat the surface with the bottom. Okay so that’s the sort of top part of the pot there. Just make sure that we don’t have any curves we don’t need there and any points. Turn on the body surface outer and you can see now we’ve got the top there, we just need to trim that around and that’s ready to go.
So that’s the top surface, next up is the bottom surface and then we start joining things together. So we can see what happens with the bottom surface here when we look at this section through the coffee pot. The inside surface is just a straightforward planer cap really. The bottom surface has got a little relief to it here, so I’m going to just draw some curves here. I have of course created a layer to do this on and I’m going to draw a line along here and going to draw a line around about here just following that direction here, and then try and adjustable curve blend between these.
Okay so this point needs to come down here somewhere, this one over there. So I just want a gradual tangent blend around there. Okay, so that looks good and let’s now draw a line here and turn off the sections and our surfaces, just for a moment. Trim all this up and join this together. Okay, if I turn on my surfaces again, go to perspective, set my C-Plane to world top and create a new surface layer here. Make that active, I can do another rail revolve. Turn off project of course while I do this. Shade that up, okay that’s my base surface there. Just a little over large.
So now we can really start to think about trimming the various pieces together and joining our various components. Now before we do this, we might want to take a copy of all of these surface layers here and put them on another set of layers, purely so that if we need to go back to the surfaces in their pre-trimmed state, we’ve got a copy of those.
Thanks for watching and please do check out the third and final video in this tutorial.