v1.23.0October 27, 2026

More reliable rounds, editable code

More fillets finish at the size you ask for. Open the new Code tab to see how your model is built and change its values by typing.

Limits

Some corners where several rounds meet at a sharp tip can still be incomplete or remove too much material. Check those previews carefully before keeping the feature.

Fillets and chamfers in older saved files rebuild as before.

Change a model by typing in its code

Every model can be read as the Python that builds it: each sketch, point, dimension and feature is one line, named after the part it makes, such as foot_profile or footplate. The numbers in it are live: change one and the model rebuilds while you type. Bookkeeping the file needs but a reader does not, such as ids, is shown faded.

Only values can be changed for now. Adding or removing lines, named parameters and sliders come later. The downloaded .py file is Cadadd Python, the subset of Python that Cadadd writes and reads back; it is not a general Python program.

Choose Code beside the feature tree (on a phone, under it).
Click a number, such as depth=8, delete it and type a new value. The model changes as you type.
Press Enter to keep it, or Escape to put it back. Cmd/Ctrl+Z undoes the whole edit in one step.
To save the code as a file, choose .py in the Code header, or Download .py in the account menu.

What this enables

Pick the edge where a branch meets a pipe, the mouth of a hole drilled across a shaft, the top edge of a low step, or the edges next to an earlier fillet, and use Fillet or Chamfer as usual. More of these edges now accept the requested size without shrinking it.

Limits

Files saved before this release keep their fillets and chamfers exactly as they were. A fillet ending where two sloped faces meet at a point, such as two of the four edges at the tip of a pyramid, may still leave selected edges unfinished or need a smaller radius.

Some turned imported shapes, including concave outlines, still refuse a finish. Small rounds against a ball or a steep cone can differ from the ideal removed volume by a few per cent because of the part’s faceted surface.

Work with the panel

The panel opens under the view cube, at the right edge, every time. The part and your picked edges stay in the uncovered part of the view, so you can watch the preview change as you set a size.

In 3D, choose Fillet in the dock and click edges of the part. The Fillet card opens at the right edge.
To move the panel, drag the bar at its top. It stays where you leave it in this browser.
To put it back, double-click the bar or press Dock.

Two distances or a distance and an angle

A chamfer can now stand back a different distance on each face of an edge, or one distance and an angle. When you chamfer a loop around a face, the first distance goes on that face for every edge of the loop.

Existing chamfers keep their equal distance. Very steep angles that would never reach the other face are refused with a message.

Select Chamfer and pick the edges, or choose Closed loop and pick an edge of the face.
Under Type, choose Two distances or Distance and angle.
Enter Distance 2 or Angle. Use Flip if the first distance is on the wrong face, then choose Confirm.

When a size doesn't fit every edge

The edges that can take the size are finished in the preview, and the others are highlighted on the model with the reason. Choose Skip this edge to leave them out, or Use … (largest that fits) to switch to the largest size the app found that fits every selected edge.

How the new rounding engine compares

We benchmarked the new rounding engine against public test suites, including the fillet tests that the open-source OpenCascade project publishes for its own kernel. 81 of those tests use shapes that all three engines below can build directly, so all three were run on the same 81.

This release: 81 of 81 finished at the requested size as valid solids, and all 81 met our accuracy rule.

OpenCascade: 79 of 81 finished as valid solids. In 2 tests its own result failed a validity check (a self-intersecting solid, and a solid that fails its own shape check).

SMLib: 68 of 81 finished. Accuracy was not graded.

A result counts as right when the material it removes is within 0.5% of the reference, or when its surface stays within the faceting tolerance at both 128 and 256 facets and gets closer as the facets increase, or when it passes a check against the exact surface. Under a stricter rule that accepts only surface checks, not volume, 76 of the 81 pass today.

These tests cover fillets only. OpenCascade's chamfer tests, its remaining fillet tests and its tests for other operations start from imported STEP files, which the app can't import yet, so they aren't included. On a separate held-out set of shapes, an earlier build finished 52 of 64 where OpenCascade finished 58; it will be re-measured. On our own 144-model public set, 143 finish fully and none are invalid.

Open CASCADE Technology (OpenCascade) is a trademark of Open Cascade SAS. SMLib is a product of Solid Modeling Solutions. We are not affiliated with or endorsed by either. Both are used only in our test tools and are not part of the app.

Fillet on a phone

The card opens along the bottom of the screen, and the part sits in the space above it. Tablets and computers work as before.

Open a part in 3D and choose Fillet in the dock. The part moves above the card.
Tap edges of the part. They stay in view while you set the radius.
To check the Feature tree while the card is open, tap Tree. Tap it again to fold it.
Close the card with ✕, or apply it with ✓. The part moves back.

Set a fillet on a phone

The card opens small, so you can watch the part while you choose the size. Everything the card can do is still there under Options.

Open a part and choose Fillet in the tool dock.
Tap an edge of the part.
Slide the Radius wheel left for a bigger radius or right for a smaller one. The part updates as you slide.
To type a radius, tap the number, enter it, and tap Done.
Tap ✓ to apply, or ✕ to cancel. Tap Options to change how edges are selected.

Everything in this release

Added

New Code tab: open Code beside the feature tree to see your model as the Python that builds it. Click any number, type a new value and the model rebuilds as you type; press Enter to keep it, Escape to put it back, or Cmd/Ctrl+Z to undo the whole edit in one step. A value the model can't take is explained right at the number and nothing changes. Edits made elsewhere, such as retyping a dimension in a sketch, update the code in place. Selecting a part highlights its lines, and clicking a line selects that part. Download .py saves the code as a file. It's Cadadd Python: the subset of Python that Cadadd writes and reads back, not a general Python program. On a phone the code opens as a sheet below the model. For now only values can be changed in the code; adding or removing lines comes later.

Improved

Fillets and chamfers now work where two round shapes meet: the junction of a pipe tee, a hole drilled across a shaft, at an angle or through a tube, two bores crossing inside a block, a boss on a curved wall or on a ball, a set-screw hole in a collar, and the groove of a V-pulley. Before, these were refused at every size.
Fillets and chamfers now work on a hole drilled at an angle, on the flats of a D-shaft (one or both, and its D-shaped end), on the top edges of a keyway, including one that runs out of the end of the shaft, and on the base rim of a cone. Before, these were refused or made smaller than asked.
The top loop of a D-shaped part, a straight edge joined to an arc, now takes the full fillet with clean corners. Before, it was made smaller than asked.
A fillet whose radius is half a rib's thickness, on both of its top edges, now makes one smooth full round. Before, one of the two edges was left out.
The upright outer edge of an L-shaped step now takes a chamfer that ends on the lower face. Before, every chamfer distance there was refused.
A fillet round the base of a boss with tapered sides, such as one on an imported part with drafted walls, now goes all the way round at the size you ask, corners included. Before, some of its edges were left out.
Rounds where a cone meets a cylinder or another cone, or rises from a flat face, now take the right amount of material, and a round where a shaft runs into a ball now builds. Before, small rounds there were off by up to 7 % and the shaft-and-ball round was refused.
You can now pick the rim of a hole drilled through an imported part, the edge where an imported part meets a feature added to it, and an edge of an imported part that an earlier fillet or cut has shortened. Before, these edges were refused when clicked.
A fillet or chamfer bigger than the face it runs along now builds at the size you ask: on the top edge of a step shorter than the radius it runs down to the lower face and meets it in a clean edge, and the same goes for a boss on a short shoulder. Before, it was made smaller than asked.
Fillets and chamfers on both top edges of a rib thinner than twice their size now meet along a ridge down the middle of the rib, and the same works on both rims of a tube's end and the two floor edges of a narrow slot. Before, they were made smaller than asked.
A fillet next to an earlier fillet now follows on from it. An upright edge rounded after the two top edges at its corner carries its round up between them and closes neatly at the top. Upright edges rounded larger than an earlier top-edge fillet carry that fillet smoothly around them. A top loop rounded larger than earlier upright fillets gets clean corners, with the upright fillets carried up into each corner. The result is the same as doing the two fillets in the other order. Before, these were made smaller than asked or left edges unfinished.
On an imported part made of triangles, a second fillet next to an earlier one now carries on around the first one's end and down the edge below it. Before, it was made smaller than asked.
Fillets and chamfers on turned imported boxes now take the full size and remove the right amount of material. Chamfers in supported imported inside corners and finishes on imported sloped sides are more accurate too. Before, these could be refused or come out a few per cent off.
A chamfer along the flat of a D-shaft now takes off the amount of material the distance calls for. Before, it took off 8 % too little.
Rounding the rims of several holes at once is much faster: six bores in a plate take seconds, not most of a minute.
Fixed: a fillet on an inside edge whose floor narrows to a point at both ends, such as a curved wall standing on a crescent-shaped ledge, was refused at every size, or shrunk to a tiny radius with only a note. It now builds at the size you ask: full where the ledge is wide enough, trimmed flush with the ledge's sides where it narrows, and tapering to nothing at each end.
Fixed: a fillet or chamfer wider than a pocket's wall could cut below the pocket's floor. On a 2 mm deep round pocket, a 3 mm fillet on its rim dug a groove 1 mm under the floor and removed more than four times the material it should. It now stops at the floor, which stays flat. Fillets and chamfers saved in earlier files rebuild as they were.
Fixed: a fillet or chamfer so large that it would take away the whole part is now refused with a plain message, and the card offers a size that fits. Before, the part disappeared and the card said Completed.
Feature cards now open in one fixed place: a panel at the right edge of the view. Fillet, Chamfer, Mate, Extrude, Revolve, Sweep, Pattern and editing a feature all open there instead of next to what you clicked, where they used to cover the part.
While the panel is open, the model slides left so your selection stays in view. If you click something right at the edge of the view, the panel opens over that spot and the model slides it back into the open.
Drag the bar at the top of the panel to move it anywhere; it stays there next time. Double-click the bar, or press Dock, to put it back at the right edge.
On a phone the cards stay a sheet along the bottom of the screen, and Fillet, Chamfer and Mate now use that sheet too.
Quick actions such as Focus surface, Fillet face, Look at and the sketch constraint buttons now appear in one strip at the top centre of the view, not where you clicked.
Fillets and chamfers now work on imported parts whose flat sides are made of triangles, such as the Cast pad sample: every top, bottom and sloped edge takes a 2 mm fillet or chamfer, one edge at a time or as a loop. Before, the Cast pad's front top edge refused every radius and every chamfer distance. A part that was exported turned at an angle to the axes is not covered yet: a fillet on it can still be refused or come out a few per cent off, so check the preview.
Fillets and chamfers now work where two extrudes meet side by side, such as an L-shaped step: the step's upright edge takes a fillet and its inside corner takes a chamfer. Before, both were refused at every size.
A fillet on an imported box lined up with the axes, across the join of two parts, or on a part drawn on a tilted plane no longer leaves a dent at its ends and now removes the right amount of material. Before, a 2 mm fillet on every edge of an imported box removed 22 % too much. If you pick only part of a straight edge that runs across a join, only that part is finished, or the card asks you to select the rest of the edge.
Chamfers on parts drawn on a tilted plane, and chamfer loops around sloped corners, now build. Before, they were refused or came out crossing themselves.
Opening or rebuilding a model now checks every fillet and chamfer the same way Confirm does. If a finish would make the part cross itself, its row shows a problem and the part is left without that finish. Before, the broken part was built without a warning. Chamfers in existing files that met at a sloped corner and crossed themselves there now rebuild correctly instead.
When some of the selected edges can't take the size, the fillet or chamfer is still made on the edges that can. The others are highlighted on the model and listed with the reason. Use Skip this edge to drop them, or Use … (largest that fits) to choose a size that fits every edge.
The search for a size that fits now works even when sizes succeed and fail out of order. It offers a round number such as 1.41 mm, and when no smaller size works it says how far down it checked and why. The card no longer suggests a smaller radius or distance when smaller sizes fail too.
Chamfers can now use two distances, or a distance and an angle. Use Flip to swap which face gets the first distance. Chamfers in existing files keep their equal distances.
Closed loop and the face actions now follow the whole outline of a flat face that is split into triangles or pieces, such as the top of the Cast pad. Before, no loop was offered there.
More fillets finish at the requested size, with benchmark results and accuracy limits explained in this update.
On a phone, while a feature card such as Fillet, Chamfer, Mate or Extrude is open, the part moves into the space between the top bar and the card, so the edges you pick stay in view. It follows the card when you pull it taller, and comes back when you close it.
On a phone held on its side, the card stands at the right below the top bar, clear of the view cube and the line of tips.
The sketch's Selection options sheet on a phone gets the same room: the part moves above it.
On a phone the top is one slim bar: the logo, the file's name (with a Demo tag on a demo file), a short Import button on demos, and your account button. A dot on the account button reminds you to sign in to save, and Sign in is the first item in its menu.
The Feature tree is a Tree tab on a phone. Tap it for a compact list with small icons; tap a row to show its edit, show and suppress buttons.
2D, 3D, Fit and Views are in a menu: tap the arrow beside the view cube.
The tools are one row along the bottom of a phone, with the most-used first: Select and Measure, then Extrude, Revolve and Sweep, then Fillet and Chamfer, then the sketch tools. The edge with more tools past it fades, so you can see the row scrolls. With the phone on its side the row shows icons only. The assistant and Contact us buttons sit beside the Tree tab.
Feature cards open as an iPhone-style sheet that floats above the bottom of the screen: ✕ to cancel and ✓ to apply at the top, the size, one line about the result, and everything else under Options. Pull the sheet up, or tap Options, for more.
Every size on a phone is a wheel: slide it left or right and the part changes as you watch, flick it to move further, or tap the number to type an exact value. Fillet radius, Chamfer distances and angle, Extrude depth, Revolve angle and Pattern copies and spacing all use it.
When a size is too big and the app finds the largest size that fits, the wheel marks it and shades the sizes that won't fit, and the line offers it; tap the mark or Use to set it.
Held on its side, a phone shows the same compact card at the right, under the top bar.
Computers and tablets are unchanged.

Fixed

Fillets along the central edge of quarter-turn and three-quarter-turn revolved parts now keep the intended round at both flat ends.
A single straight edge ending at the tip of a cone, on a ball or against an earlier fillet now removes the right amount of material in more cases.
When a set of rounds cannot be made accurately, more requests retain the edges that fit and explain which edges remain unfinished.
Fillets that taper to a point at both ends can now finish on supported intersecting curved surfaces.
More selected straight-edge fillets finish together across pointed corners.
Rounded corner transitions are smoother at lower display detail.
Fillets stopping on pointed supports retain their correct shape when display detail increases.
A corner snapped or constrained onto another line no longer joins two closed areas into a profile that refuses to build.
If a saved profile contains two shapes that only touch at a corner, pick one area again, or edit the sketch so the shapes share an edge.
Revolve and extrude failures show a short recovery instruction, with the original diagnostic under collapsed Technical details.
Incorrect fillet patches at pointed ends are detected even when the resulting solid is closed.
Selecting touching sketch areas no longer hides a depth, angle or axis problem behind advice to edit the sketch. The original diagnostic remains available in Technical details.

Other improvements

Fillets with incorrect patches at pointed ends now show a warning instead of accepting the wrong shape, even when the solid is closed.
More fillets finish where they taper to a point at both ends or where selected edges cross sloping faces; rounds stopping on pointed supports keep their shape as display detail increases.
More fillets keep their requested radius at flat or curved ends and where several rounded edges meet. Corner transitions are smoother at lower display detail.
A fillet along the central edge of a partial revolve now meets its flat ends cleanly instead of scooping away too much material. Single rounds ending on a cone, ball or earlier fillet are more accurate too; complex pointed corners can still be inaccurate, so check their previews.
Invalid revolve angles and extrusion depths now ask you to correct the amount even when the selected sketch areas touch, instead of asking you to edit the sketch.
Sketch areas whose corner meets the middle of another line can now be revolved or extruded separately. If two shapes only touch at a corner, pick one area or edit them to share an edge; failures show a recovery instruction with technical details folded away.
Fillets and chamfers now work where two round shapes meet: the junction of a pipe tee, a hole drilled across a shaft or through a tube, two bores crossing inside a block, a boss on a curved wall, a set-screw hole in a collar, and the groove of a V-pulley. Before, these were refused at every size.
Fillets and chamfers now work on imported parts whose flat sides are made of triangles, such as the Cast pad sample: every top, bottom and sloped edge takes a 2 mm fillet or chamfer, one edge at a time or as a loop. Before, the Cast pad's front top edge refused every radius and every chamfer distance.
Feature cards now open in one fixed place: a panel at the right edge of the view. Fillet, Chamfer, Mate, Extrude, Revolve, Sweep, Pattern and editing a feature all open there instead of next to what you clicked, where they used to cover the part. While the panel is open the model slides left so your selection stays in view; something you click right at the edge of the view is where the panel opens, so the model slides it out from under the panel. Drag the bar at the top of the panel to move it anywhere; it stays there next time. Double-click the bar, or press Dock, to put it back. On a phone the cards stay a sheet along the bottom, and Fillet, Chamfer and Mate now use that sheet too.
On a phone, a feature card no longer hides the part you are working on. While Fillet, Chamfer, Mate, Extrude or another card is open, the part moves into the space above the card so the edges you pick stay in view, and it comes back when you close the card. The same happens while a sketch's Selection options sheet is open. Held on its side, the card stands at the right, below the top bar, clear of the view cube and the line of tips.
On a phone, the app is compact and made for touch. The top is one slim bar: the logo, the file's name (with a Demo tag and Import on a demo), and your account button, where a dot reminds you to sign in to save. The Feature tree is a Tree tab that opens a short list, and 2D, 3D, Fit and Views are in the menu beside the view cube. The tools are one row along the bottom, most-used first, with a fade on the edge that has more (icons only with the phone on its side); the assistant and Contact us buttons sit beside the Tree tab. Feature cards open as an iPhone-style sheet with ✕ and ✓ at the top, the size on a wheel you slide to change the part as you watch (tap the number to type one), one line about the result, and the rest under Options; pull the sheet up for more. Fillet radius, Chamfer distances and angle, Extrude depth, Revolve angle and Pattern copies and spacing all use the wheel, and when a size is too big the wheel marks the largest that fits. Computers and tablets are unchanged.