§1c — Colour
PathBlend
The other way to make a gradient. Instead of alternating lines of two filaments, PathBlend builds a physical ramp inside the layer: the first filament gets thicker as it crosses the surface, and the fade you see is light travelling through more and more of it.
- no gate
- print-verified
- the most fragile part of the engine
Where ColorStitch Painter›Pro›a pass set toPathBlend Half orFull›ADV…
Two ways to fade
ColorStitch gets you from blue to yellow by giving more and more of the fill lines to yellow. Every line is still one filament at full thickness, and what changes across the surface is how many of them are yellow. Up close you can count them.
PathBlend changes the thickness instead. Every line is printed with the same filament, and what changes is how tall that line is: 0.04 mm at one edge, 0.18 mm at the other, with one real print-height step per fill line in between. A translucent filament that is 0.04 mm thick barely tints what is underneath. The same filament at 0.18 mm nearly hides it. Run that across a surface and you get a continuous fade with no dithering anywhere in it.
ColorStitch
Ratio of lines. Works with opaque filament. Grainy on small surfaces because a handful of lines cannot express a fine ratio.
PathBlend
Thickness of material. Needs some translucency to read at all. Smooth even on modest surfaces, because each line carries its own height rather than a vote.
That is also why TD matters more here than anywhere else. Give PathBlend an opaque filament and the ramp is invisible: 0.04 mm of it already hides everything, so the extra 0.14 mm changes nothing you can see. Have a look at the optics page if you want the numbers.
Half and Full
| Kind | What gets printed |
|---|---|
| PathBlend Half | The ramp alone. It climbs from its floor and nothing fills the space above it, so the surface is genuinely thinner where the ramp is low. |
| PathBlend Full | The ramp plus a cap in a second filament, taking whatever height the ramp did not. The layer stays full height everywhere, and the two colours trade places across the surface. |
Picking either one collapses the zone to a single pass. PathBlend is always one full-height gradient; it does not stack with other passes inside the same zone.
The ADV editor
This is the cross-section graph the ADV… button opens from the Painter's Pro
tray. Horizontal is position across
the surface. Vertical is real height in millimetres. Two handles do all the work.
ColorSci::blend_stacked.
| Handle / control | What it sets |
|---|---|
| Low handle | Where the ramp starts to rise, and how low its floor sits. Drag it right and you get a flat start zone before the climb begins. |
| High handle | Where the ramp finishes rising, and how high its top reaches. Drag it left and you get a flat end zone after it is done. |
| floor | The ramp's starting height in mm, at the low edge. |
| ramp end | The ramp's top height in mm. In Half this is locked to the full layer height, since there is no cap to fill the rest. |
| Mode | Linear / Ease In / Ease Out / Ease In-Out. Only an older engine path that normal settings no longer reach uses this; the per-scanline staircase that actually prints today ramps linearly in t, then applies the start and end zones on top. |
Left at their defaults the handles sit at the two edges and the ramp spans the surface, which is what PathBlend has always done. That is deliberate: the whole start/end zone extension was built so that defaults produce exactly the G-code they produced before it existed.
The "techo"
In Full mode you can drag ramp end all the way up to the layer height. The cap then has zero height in that region, so none of its colour prints there at all. This is the move for a translucent filament that needs proper opaque coverage instead of a thin sliver of the wrong colour sitting on top of it. Try it in the demo: push the high handle to the ceiling and watch the cap colour disappear from the right-hand end.
Aiming the gradient
Each fill line carries one height, so the ramp has to climb across the lines, and since
2.4.6 that is exactly the direction it takes: at right angles to the fill lines, on any
shape. To aim it, set the pass's fill angle in the
ColorStitch Painter, next to the Mode button, with
-1 for auto or a fixed 0–359°. The ramp turns with the lines.
Before 2.4.6 the direction came from where the middle of each line fell. On a square or a round part that gives the same answer. On a long or irregular one it does not: measured on a keychain with its lines at 45°, the ramp ran 80° away from where it should, almost along the lines, and that was the hard diagonal band some people saw where a smooth fade should have been. Measured after the change on six test parts, all with lines at 45°, the ramp runs at 135° on every one of them.
A hole no longer splits one line into two heights either. When a hole cuts a fill line in two, both pieces get the same height.
When it used to come out flat
Worth knowing even though it is fixed, because it explains the shape of the thing. The
staircase produces one height per fill line, which quietly assumed that the
surface pattern hands the engine one line at a time. Monotonic line does. Plain
Monotonic, and every other pattern that chains its lines into one long zigzag,
does not: the whole surface arrived as a single line, got a single height, and the gradient
came out perfectly flat.
It showed up most on bottom surfaces, whose default pattern is
Monotonic, while tops set to Monotonic line looked fine. The same
top would have broken with the same setting. Since 2.4.0 PathBlend asks for unchained lines
itself, so the gradient no longer depends on which surface pattern you picked.
Handle with care
The per-scanline staircase model, one physical print-height step per fill line, each step
resting on the layer below and on its neighbours, is validated and must not be disturbed
by unrelated changes. If you are reading this as someone who might touch the code: the
model is written up in docs/ and the floor / ramp-end / start-zone controls
are a deliberately safe extension of it.
A more ambitious idea, letting the ramp rise and fall inside one pass instead of always climbing, was considered and set aside. The current staircase cannot do it without risking unsupported overhangs at the print head. It would need a different, multi-pass engine, closer to how the Bump Mapping Editor works.
The catch
- It needs lines to work with. One height per fill line means a surface with twelve lines gives you a twelve-step gradient. On small surfaces the ramp is visibly coarse.
- It needs translucency. With an opaque ramp filament the height changes and the colour does not.
- Penultimate is off limits for now. PathBlend on the penu zone has a gradient-direction bug on multi-stair objects, so it is restricted to the Top zone. The engine supports it; it comes back when the bug goes.
- Half mode really does leave a thinner surface. Nothing fills the space above the ramp. That is the point, and it is also a thing to check before you print something that needs a flat top.
- The preview does not draw Z variation. Orca's G-code preview renders every extrusion at nominal height, so the staircase looks flat there even when the G-code is right. RealColor composites the colour correctly; the geometry still reads flat.