Surface Manipulation and Analysis in Rhino 9

Rhino 9 Surface Evaluation and Manipulation - Video Chapters and Transcript

Video Chapters - This video is split into chapters, these are:

00:00 - 00:30 Welcome and Intro to Simply Rhino
00:30 - 01:25 Introduction
01:25 - 03:10 Primary Surface Creation Process
03:10 - 03:33 UVN Indicator NEW in Rhino 9
03:33 - 04:25 Gumball UVN NEW in Rhino 9
04:25 - 04:55 Normal Direction Drag Strength Slider NEW in Rhino 9
04:55 - 06:40 Soft Transform Overview NEW in Rhino 9
06:40 - 07:24 Soft Transform Radial Control
07:24 - 08:01 Soft Transform Along Object Control
08:01 - 09:37 Soft Transform Boundary Constraints
09:37 - 10:00 Secondary Transitions Process
10:00 - 11:22 Zebra Enhancements – NEW in Rhino 9
11:22 - 14:07 Global Edge Continuity – NEW in Rhino 9
14:07 - 21:14 Short Tutorial – Adding Styling Feature with Soft Transform
21:14 - 21:50 Outro and End

Video Transcript - If you want to follow along with a separate transcript we trust you'll find the following useful. The transcript starts at 00:30 with the video introduction:

Hi, this is Phil from Simply Rhino. I’d like to take a look at some of the new surfacing and modelling tools in rhino 9 and I’m going to look at these tools in the context of developing this industrial design concept model of a cylinder cleaner.

Streamlining workflow and evaluation tasks

In this video I’ll be concentrating on surface manipulation and evaluation and how at the start of a project Rhino 9 can streamline both initial primary surface creation and then how these improved tools can help us in evaluating secondary surfaces like transitions and blends. Finally, I’ll look at creating and adjusting styling details like these ridges whilst maintaining curvature continuity.

The main volume of this product can be thought of as a box comprised of six double curved surfaces. Once these primary surfaces have been established the sharp intersections can then be blended to create the secondary transition surfaces.

Primary Surface Creation with Rhino 9

The primary surfaces here are built from some two-dimensional curves which are then extruded to create simple two-dimensional surfaces. I’ll change the degree of the side surface to make this degree five in both U and V and then trim the top of the side surface away.

Next I’ll use Refit Trim to create an untrimmed side surface before mirroring this along the centreline of the product. Then I can create a simple loft before once again using Change Degree to create a single span degree five surface.

Having worked out where I’d like the front curved surface to start, I can trim the side surface before once again using Refit Trim to create an untrimmed surface. Using an untrimmed surface is advantageous for matching as although it’s possible to match to a trimmed surface edge it’s not possible to match with a trimmed edge.

One of the things that we very quickly need to do when we are roughing out a model is to add some crown or double curvature to the primary surfaces and this is where the new tools in Rhino 9 are really useful.

UVN Indicator - New in Rhino 9

So, let's look at this top surface first of all and turn on the Control Points. The first thing that is worth noting is that Rhino now gives us a UV indicator for the surface this is really useful in helping us when, for example, selecting rows or columns of points.

Previously in Rhino when moving and adjusting surface points, Move UVN would be the tool of choice – and this is still available in Rhino 9. Move UVN is okay but it’s an indirect way of adjusting points relying on sliders with a distance setting.

In Rhino 9 surface points can be edited directly with the Gumball and if I set the Gumball to Align to Control Polygon then when I pick a point, you'll see the Gumball Indicator now constrains to the U, V and N direction. If multiple points are selected here I can move all of them in, for example, their local Normal directions even though the indicator snaps to the last selected point.

I can also, of course, change the Drag Strength and if I select Drag Strength from the Gumball Options here a drag strength dialogue box appears and, when the Control Polygon Alignment mode is set, there is a separate drag strength control for the Normal direction because very often modellers want to move points across a surface quickly whilst having a more subtle control in the normal direction.

New Rhino 9 Options with Soft Transform

Now let’s look at how to add the crown or double curvature to the surface and I can do this with Soft Transform from the Transform toolbar. Historically, tools like Soft Transform have been associated with meshes and SubD’s where the given transformation is washed away over a spherical radius of influence. In Rhino 9, however, we can also use an ‘Along Object’ option to use the control point structure of the surface.

When using the ‘Along Object’ option the Surface Count in U and V is used instead of the Radius Slider and the movement falloff can be calculated over a given number of points. Here you can see points being highlighted or removed from the transformation as I move the sliders.

Additionally, I can set ‘Boundary Constraints’ to G0, G1 and G2 so here if I want to constrain the two long edge positions of the top surface, I can set these to G0. Then, I can pick the middle two rows of points using ‘SelU’ and pull them in a Normal Constrained Direction with the Gumball to create the crown.

The coloured shading gives an indication of how the point movement influence washes away over distance. Now of course, you may want to use a more considered method of creating the double curvature as a project progresses, but this is a great way to quickly advance the creation of initial surfaces.

Let’s look a bit closer at the workings of Soft Transform. Here I have a Degree 5 surface that I rebuilt to have 21 points in U and V, and I have the Gumball alignment set to Control Polygon. I’ll pick a single point at the centre of the surface and turn on Soft Transform. I can still use the Spherical Distance Measure with NURBS control points and you can see that as I move the slider to change the radius how this is influencing a spherical area and if I pull this single point upwards in a Normal direction how the movement is washing away over the radial distance.

If I now set the Distance Measure to Along Object I’ll see that the distance is now constrained over a designated number of points. So by setting different values in U and V, I can move just one point in a Normal Direction and achieve this elongated styling feature. Now of course, it’s not good practice to have surfaces that are full of control points like this example - so later on in the video I’ll look at how something similar can be achieved with more limited control points.

Boundary Constraints

Next, lets look at the Boundary Constraints. Here, I have two Degree 5 Single Span surfaces that are matched for G2 (Curvature) Continuity. And I have six control points selected here. I’ll turn on Soft Transform with a Control Point count of 3 in both U and V which implies that all of the surface points could be moved when I move the six highlighted points with Soft Transform.

Next, I’ll turn on Boundary Constraints here. The boundaries will initially be unconstrained, but I can click on the annotation dot at the appropriate edge to add constraints. If I set the edge constraint here to G0 (Positional Continuity) then the row of points along the edge will not be moved. If I step up the continuity to G1 (Tangency Continuity) then the next row will be fixed and if, finally, I step up to G2 (Curvature Continuity) then the next row will be constrained.

Now when I move the six highlighted points in, for example, the Normal Direction I'm getting the full range of Soft Transform movement in the ‘V’ direction but the fall-off movement in ‘U’ is constrained in order to maintain Curvature Continuity. So, this is very useful addition to the Rhino toolset when setting up initial surfaces for a concept model.

Rhino 9's Surface Evaluation tools

Let’s now go back to the Cylinder Cleaner model and having established the crown on the top and sides I could then pretty easily create the front surface with, for example, Blend Surface before trimming up the four surfaces and adding a Blend Edge transition. It’s at this stage that Rhino’s Surface Evaluation tools become important, and in Rhino 9 the Zebra tool has been considerably enhanced.

The first obvious improvement is that the Zebras now have a ‘Static’ option which means that the Zebra Stripes are fixed to the object in question and don’t move as I manipulate the view. It’s still possible to use the ‘old’ method as I can uncheck ‘Static’ but I think in most use cases the ‘Static’ option is more useful. I can set the direction of the stripes to X, Y or Z or even a custom direction between two points – in this example setting the stripes in Y seems to make most sense.

I can also change the Frequency of the stripes, the Rotation, the size of the Stripes and the Blurring of the edges. Additionally there is now a ‘Mode’ control where I can choose from a number of different styles or patterns such as Radial, Grid, and Dots - each of which can be configured per the zebras. There’s also a Rainbow option that can make it easier to follow particular light lines as the flow across the surface.

Many modellers would use these visual analysis tools initially and then, when appropriate, move on to a more mathematical mode of analysis in particular to check the continuity between pairs of edges. Previously we could use the Edge Continuity command to do this but that could sometimes be a laborious process as pairs of edges needed to be added one at a time. Rhino 9 has a new feature which can analyse all the edge pairs of a selected part or model.

To run this, I’ll go to Analyze > Surface and choose Global Edge Continuity. I’ll then pick the cylinder cleaner body, and I’ll get immediate feedback on the edge continuity. I can check separately for G0 (Positional) continuity, G1 (Tangency) Continuity and G2 (Curvature) Continuity and the preferred approach is to step through these three conditions starting with G0.

I can see and change the tolerance settings here – and you might want to do this on a project specific basis – and in the lower pane here I’ll see a readout for all the pairs of edges. The edge pairs are numbered both in the list and on the model.

Looking at the result here I can see that all my edge pairs pass check for G0 and, stepping up to G1 shows that all the edge pairs are tangent. Stepping up to G2, however, shows that I have two problematic edge pairs and if I pick one of these edges from the list, I’ll be able to see more information on continuity across the edge and where the troublesome portion might be.

Looking at the top of the Global Edge Continuity Panel, I currently just have Labels selected but I can also show Graphs or both Labels and Graphs. The curvature graph will only display for edge pairs that are out of tolerance and has similar settings to the existing Curvature Graph command. In this instance the graph again helps to show which part of the edge is causing the problem.

With a case like this I think the edge continuity issue likely stems from the edge positions of the lower surfaces, so rather than just trying to fix the blend surface I’d probably go back to the primary surfaces and adjust where the front edge of the side surface meets the top surface.

Let’s now put some of these new features together to look at how we can add a feature similar to these raised styling bulges here that wash away into the top surface. I'm going to make something similar to that which we're seeing here but they won't be identical.

I’ll start with a ‘clean’ version of the top moulding and copy this onto a new layer. Now at the moment this is modelled as a closed polysurface, but I’m only really interested in the top surface so I’ll detach this and hide the other polysurface parts.

The top surface is a trimmed single span surface and providing I’ve modelled this correctly it will be symmetrical about a World X axis centre line. Assuming that I want symmetrical detailing on each side I can split the surface along its centreline and create both sides at once. I’ll go to Surface > Surface Edit Tools and run Split At Isocurve, making sure that the ‘Shrink’ Option is turned On – this will create an untrimmed edge when I split the surface. I’ll toggle the Direction to U, and with the Intersection Snap enabled, I can snap to the Intersection here to find the centreline of the surface.

Having split the surface I can now delete the right half, before splitting again with Split At Isocurve making sure that the Shrink Option is enabled - this time I’ll split out a long thin surface. Finally, I’ll repeat the process this time splitting in the ‘U’ direction to define the rectangular area inside of which I’ll create the bulge.

So just to summarise so far, I’ve split a Degree 5 single-span surface into five segments with the result that each of new segments is a Degree 5 single-span surface itself and the rectangular surface on which I’m working has no trimmed edges.

If I turn on the control points for the ‘bulge’ surface, we can see there are six points in U and V and I really need more points to work with. If I want to maintain the single-span methodology, then I can do this by using Change Degree. So, I’ll run this from the Surface toolbar and set the Degree in U to 10 and V to 7. Having done this, I’ll select all the surfaces and Mirror them about the World X axis with History On.

Now, I can select the copied surfaces and apply an Environment Map to them, and of course at the moment the surface looks completely smooth.

I’ll now turn on the Control Points for the surface and then pick the two central points and, it may help to momentarily turn off the Gumball to do this. Then I can open up the drag strength slider and then go to the Transform toolbar, open up Soft Transform and make it active. In some cases, I may need to increase the point range in these sliders and I can this by right-clicking on these small arrows here and I’ll see a dialog box where I can set new Minimum and Maximum values.

For this example, I want the influence to initially extend all the way across the surface and then I’ll turn on the boundary constraints. I’ll set the constraint for each edge to G2 and as I do this, I’ll see that each edge will have three rows of points that will not be moved in the transformation. Now of course I could do something similar with Move UVN but the real advantage here is that I’m only moving two points and the Soft Transform tool is moving the remaining available points whilst maintaining the G2 continuity.

I’ll now lower the drag strength for the Normal slider and move the two selected points upwards to create the styling feature. If I look at the mirrored side with the environment map I can see the result, and this is giving a very organic looking feature that blends seamlessly into the main surface.

If I want to create a feature that doesn’t wash away over such a big area, so that it is slightly more defined at the front and back, then I can add some knots in the V direction at each of those two ends. So, I’ll undo the previous steps to return to the starting surface.

In order to push the soft transform area of influence closer to the front and back I’ll add two knots at each end – as I want three rows of control points at each end that will be untouched with the transformation. I’ll go to Edit > Control Point > Insert Knot and pick the surface and then Toggle the Direction to V. I’ll place two knots here and this will give me two additional rows of control points at the edge.

I’ll repeat this process at the front Edge. Now, of course, doing this will mean that the surface is no longer a single span Bezier surface, but it is a legitimate way of quickly adding surface control without creating unnecessary control points.

I’ll momentarily turn off the Gumball and pick the two mid points as previous and then move the U slider in Soft Transform to influence the appropriate number of points. The G2 Edge constraint will be remembered so I’ll now push the two points upwards with the Gumball. Looking at the result with the Environment Map, I now have something that is more defined at each end which I think is an improvement over the previous version.

So now I can turn off Soft Transform and the Environment Map before showing the hidden parts – and, if all has gone according to plan, I should be able to join these parts together into a closed solid polysurface, now of course, I’ll see the History Break warning here but this is to be expected.

I think this is a pretty quick way of doing styling variations whilst maintaining surface economy and the great thing about Soft Transform in this method is that I can look after the shaping and Soft Transform looks after the continuity.

That’s about all I wanted to cover in this Rhino 9 Surface Evaluation and Manipulation video, thanks for watching and, please feel free to leave any comments below. If you have found this video useful then please hit the ‘like’ button and remember that to keep up with all the latest developments in Rhino, you can subscribe to this channel. At Simply Rhino we offer training for Rhino and all its key plugins so checkout our website for more details. Thanks again for watching and I'll catch up with you in the next video.