In most cases you’ll draw feathers from a reference image and trace the outlines. If you want to create a complete feather set, then you should assemble individual photos to a feather atlas. There, different types are depicted side by side. You can sometimes find appropriate images in online resources, but in most cases you have to create an atlas yourself. In such a case it’s important to mind the feathers' relative scale.

Here’s the reference image for this workshop with details of the tip and shaft areas.

1. Move the mouse cursor over the viewport and press 2 to switch to top view.

2. Now press D to open the Display Options.

3. Open the Background tab, then click the Top tab.

4. Make sure that Disk File is turned on and click the icon to load a reference image.

5. If the image is too large or too small, adjust its size with the Image Scale parameters. Mind the feather’s actual scale! In this example, the feathers' length is approximately 20 cm.

6. With Image Offset you can change the image’s viewport position.

It can sometimes help to hide the viewport grid with a click on . If you want to check your feathers without the background, open the Display Options again. On the Background tab, turn off Display Background Image/Video.

Scale is important and some reference images even provide a scale. This will help you to keep relations and create a realistic appearance. Inside Houdini it’s sometimes not so easy to maintain proportions or estimate an object’s size. Of course there’s the viewport grid and you can adjust its default spacing.

1. Hover the mouse over the viewport and press D to access the Display Options. There, open the Grid tab.

2. Go to Grid Spacing. The default spacing is 0.2; that’s 20 cm. For large feathers, a value of 0.1 (10 cm) is sufficient. For small feathers, you might need values of 0.05 (5 cm) or smaller.

You can change Grid Spacing at any time, depending on whether you're working on large or small feathers. However, a very dense grid can sometimes be distracting. In such a case it can be helpful to add a reference object like a Box SOP or a Line SOP. The advantage with objects is that you can position them precisely where you need them. Once you've found a working position, click the object node’s red Lock flag to protect it from changes.

Now you can start to trace the feathers with the Curve SOP. If you're familiar with 2D illustration programs, then you’ll immediately know how to draw curves and refine their shapes interactively. If you're new to curve drawing, please read the node’s help. There you can find valuable tips and workflow descriptions.

Here you can see the complete network for this workshop. This basic setup will be the basis for all following guides and explanations. Don’t forget that this network is located inside a Geometry OBJ on the obj level.

Here are a few tips for tracing feathers.

1. On the obj level, press ⇥ Tab to invoke the Tab menu. From there, create a Geometry OBJ. Rename the new node to feathers.

2. It’s important to make the feathers visible in the viewport. To do this, open the geometry node’s Misc tab and turn on Shade Open Curves in Viewport. This option will turn the area between the curves into a solid object.

3. Double-click the geometry node to dive inside.

When you take a closer look at the barbs, you can see that they all share more or less the same amount of curvature. Only barbs near the shaft are more rounded than those near the feather’s tip. The barbs on the reference photo, however, show different curvatures and angles. Profile curves help you to control the barb’s curvature. Drawing a profile curves works exactly as drawing the feather’s rough shape.

1. Add another Curve Bezier SOP and trace the curvature of some barbs. Houdini will interpolate the barbs between the profile curves. For better results, draw separate curves for the barbs on the left or right side of the shaft. Profiles don’t have to be symmetric or share the same number of points.

2. Rename the new node to profiles.

Normally you don’t need as many profiles as shown in the image below: two or three curves are often enough.

Names play an important role with feathers, esp. when you work with different types. Houdini’s feather system provides various methods to add names, so they're discussed separately on the Feather naming page. We recommend reading this page, before you start to apply names, because there are cases, where the name attribute is deleted.

Right now, you only have the feather’s outlines, but real feathers show clumps, splits and barbs of different length. Left and right vanes are often differently shaped, and there are also fluffy down and countless transition forms. Before you start to add details, you have to distinguish between a feather’s fundamental states.

• Condensed feathers have virtual barbs and this makes them very very resource-friendly. Furthermore, network setups are normally less complex, but possibilities are slightly limited.

• Uncondensed feathers consist of real curves with points. You have generally more possibilities to shape your feathers, but this state needs more resources. Uncondensed networks are often more complex, because you can create separate streams for shaft, left and right barbs. You also have to manually promote some important attributes.

• Houdini’s feather system provides a Feather Match Uncondensed SOP to reconvert a feather into its condensed state.

• For rendering, consider to turn condensed feathers into packed primitives by adding a Pack SOP after the Feather Template from Shape SOP.

Condensed workflows

• Feather clumping

• Guide processing and noise

• Feather blending

Uncondensed workflows

• Accessing feather components

• Down design