"Subdivide Mix Layer" sub-layer heights do not match percent blend if not 50/50

[Wombleyy]

Is there an existing issue for this problem?

• I have searched the existing issues

Snapmaker_Orca Version

2.3.4 beta

Operating System (OS)

Windows

OS Version

Windows 11

Additional system information

No response

Printer

Snapmaker U1

How to reproduce

I am reposting this as a duplicate of Issue #111 reported in the community fork which @ratdoux is actively exploring:
ratdoux#111

When using % blends and Subdivide Mix Layer (SML) for values other than 50%/50%, the percent mixture does not match the actual resulting sliced sublayer height. You must overshoot in order to reach the desired layer height splitting. Because the color preview appears to use the % mix and the layer height does not match, this results in a bigger mismatch than expected.

1. Desire is to do a 33%/67% (1:2) ratio mix.
2. Create a blend that is 33%/67% of two colors
3. Use this blend to color the model with SML properly enabled.
4. Slice the model
5. View the sliced model preview perpendicular to the surface.

Actual results

6. Observe that the smaller 33% layer is thicker than 33% of one layer.

Example for 33% magenta + 67% white:

I have confirmed with print testing when compared to layer stacking without SML, comparing 0.08mm layer stacks of 2:1 to SML layers in 0.24mm thick main layers with a 2:1 split the SML colors are biased toward the central 50/50 color in Local Z mode.

I have not confirmed but do expect that gcode also shows the subdivided layer splitting is not as requested.

Expected results

6. Expect that the layers are split by z height according to the requested mixing ratio.

Example for 33% magenta + 67% white:

Project file & Debug log uploads

None

Checklist of files to include

• Log file
• Project file

Anything else?

Other debugging observations...

1. For a desired 33%/67% split with 0.2 mm layer height, setting instead a mixture of about 25%/75% produces the desired 1:2 blend.
2. For a desired 33%/67% split with 0.24 mm layer height, setting instead a mixture of about 21%/79% produced the desired 1:2 blend.

The ratios needed for 1:3 mixtures also need to be more imbalanced than 25%/75% and do not appear to be due to layer rounding error.

I'd call this a significant bug for producing the desired and previewed color mixture that may otherwise escape detection by the user.