Sketch constraints and splines

Tutorial series: Sketching fundamentals


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What you'll learn

Craft a bottle model and enjoy updating in real-time to fit your exact design vision. Changed your mind about design details? No problem. Give your sketch a new form and develop your model working with the spline tool, tangent constraints, and design history.



Let's create this time a more detailed model and we will do this from the front view. So I go to front, move the scene down a little bit, go to Sketch and select the line command. And then from the origin, I will draw a line to the left side and type in 30 millimeters for the radius. I can move this around. I align this to the grid.


and left mouse button click. Press Escape. Zoom out a little bit. I go to the endpoint at the center of the sketch, click, and then I drag out a new line straight up and enter 170 millimeters. Press Enter and press Enter. So this time I accepted the dimension and also the orientation. The grid is very useful for drawing lines horizontal and vertical.


I zoom in to the top here, I draw a line to the left, 10 millimeters, click, then one line down, 30 millimeters. I can press Enter, Enter, and then I press Escape. You see here, we have dimensions. I can move these dimensions so I can see the sketch better. We can adjust these dimensions too.


On the left side, I will draw from this left endpoint, a line straight up a little bit. And then I will go to arc and draw an arc from this endpoint to the last endpoint. Click, and then I can move this arc a little bit like this. I press escape. Now what I would like to do is to make sure that


The arc and this line are tangent, so 180 degrees. I can add a tangent constraint. I would also like this line and this arc to be terminating perpendicular. There's no command for this, but what we can do is we can simply say the angle between the arc and the line should be 90 degrees, and that is perpendicular. You see that actually our sketch


might have adjusted a little bit in unpredicted ways, because what we didn't do yet, we didn't constrain the sketch. So before we continue, let's undo the step and check this out. Here's the end point. This one I do not want to move, so I lock it. If I click a point, you can see everything can move, but I want my vertical and horizontal lines all to be horizontal and vertical.


So I select all those and add a horizontal vertical constraint. Now, if I click on a point, this one I can move because this line is actually not dimensioned, but the other points are all static. Now, if I go ahead and say the angle between the arc and the line should be 90 degrees, everything updates exactly the way how I want. Now, if I go ahead one more time,


A test you see by adjusting this height, everything flows with it. So this is now a fully constrained sketch. I can exit the sketch, position my view, select the sketch profile, select a Z-axis, and then I call the Revolve command and there is my bottle. I would like to have a sharp corner at the bottom.


So what I will do is I'm going to go to Items, hide for the moment this bottle, show my sketch, go to the front view. I zoom in a little bit, click on the sketch to go into sketch edit mode. There is the arc command. I draw in an arc, escape, select the arc, select the line and select the tangent constraint, the same here.


And now what I can do is, you can see how I can slide this arc and specify the radius, or enter the radius manually. Then when I go back and show the bottle, you see that we still have a sharp edge. Let's go to the history. There's a revolve command.


Here is the selection for the profile. And I will shift click to here to just select this sketch profile. Click Done and everything is updated. When we have all these dimensions, so constrained edges or angles, you can see that even outside the sketch, we can now go ahead and adjust the value of the sketch.


And then the whole design will be updated too. So we do not have to go into editing the sketch. We can do it from the outside. This works very good. Let me show you now how we can take this shape of a vessel and turn it into something more interesting looking. For example, the body of


a soda bottle. I will hide this body, so it's gone. Then I will select this top arc, press Delete to remove it. And then this point I move down and into the opening, I would like to add a spline. Here's a spline icon. If you double click, you get the menu. Select the control point version. Then I can click, I click somewhere else.


I click somewhere else one more time, one more time, and then I stop at the end point. Press Escape one time to stop the drawing and press Escape. So we stop also the Spline tool. Now I would like this spline to flow tangent into this line. We can do this by selecting both and adjusting the radius.


adjust the angle or click Tangent. And you see this point now was moved to be tangent to this line. So the same here with the bottom. And now when you see you by moving the tangency points, and I have this point in between, we can very nicely style this bottle.


When we exit the sketch, you will see there's no body anymore. Let's go to History. We have actually inside the Revolve command an error. We changed the sketch. So we have to repair this. This is very easy. Click Fix. You see the old profile, just click on the new, change sketch and click Done. And that it is. There's no more body.


Now, when we go back to the sketch, we can adjust the sketch and pay attention to how beautifully our design updates in real time. Sometimes when you move points around and they snap onto projected guidelines, you can see it will add constraints. To remove such a constraint, like in my case, I select it and press Delete. And now this point.


I can move out again. There we are. That is actually how easy it is to take one sketch and then change it into a new form and then continue developing your bodies.


About the instructor


Claas Kuhnen is a German 3D designer known for his strong interdisciplinary background in product, space, and animation design. He holds an undergraduate degree in Color Design for Interior and Product Design from the University of Applied Science and Art in Hildesheim, Germany. He further pursued his education and obtained a Masters in Fine Arts in 3D Studio Art with a focus on Jewelry Design and 3D Animation from Bowling Green State University.

As a designer, Claas Kuhnen is particularly interested in design-informed solutions and exploring the relationship between consumerism, products, and their impact on society. He engages in a wide range of projects, including furniture design, interior and exhibit design, consumer product design, and medical product design.

In his research and studio practice, Claas Kuhnen delves into the application of a modern multi-application and interdisciplinary workflow. His areas of investigation encompass parametric, generative, and subdivision surface modeling, as well as AR (Augmented Reality), VR (Virtual Reality), photogrammetry, and AI-powered tools. He collaborates with various national and international universities and companies on research and design projects, contributing his expertise and exploring innovative approaches.

Claas Kuhnen's design projects span diverse domains. For instance, he has designed exhibit artifacts for The Henry Ford Museum, developed medical devices for the Department of Pharmacy Practice, and undertaken interior design projects that serve the community. His work showcases a keen understanding of the intersections between design, technology, and societal impact.

In addition to his design practice, Claas Kuhnen is actively involved in teaching and sharing his knowledge with students. His classroom experience is strongly influenced by his diverse research background, providing students with a modern, interdisciplinary, and competitive education.

Furthermore, Claas Kuhnen's work and techniques have been featured in exhibitions such as Autodesk University, SIGGRAPH, SOFA, and SNAG. He actively engages in educational collaboration efforts with both national and international universities and serves as a Matter Expert for leading design software companies, contributing to the advancement of design tools and methodologies.

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