Anatomy of a .milk file

A .milk file is plain text, one key=value pair per line, one preset per file.

Keys and values

Rule	MilkDrop 2.25c	projectM
Where the key ends	At the first = or space (state.cpp:96–111)	Same (find_first_of(" ="))
Key case	Case-sensitive	Lower-cased, so case-insensitive
Duplicate keys	—	The first occurrence wins ("to mimic Milkdrop behaviour")
A value that does not parse	The default is silently kept	The default is silently kept
Booleans (bWaveDots, …)	Any nonzero value is true	Only values > 0 are true
File size	—	Files over 1 MiB, or containing a NUL byte, fail to load

In practice:

• Don't put a space before =. zoom =1 stores key zoom with value =1, which does not parse, so zoom silently stays at its default. This happens in both programs.
• bWaveDots=-1 is true in MilkDrop and false in projectM. Write 1.
• PSVERSION_comp=3 works in projectM but not in MilkDrop. Match the case MilkDrop writes.
• [preset00] is a leftover from MilkDrop 1. Neither parser needs it, but MilkDrop writes it, so keep it for tools that expect it.

The version header decides which shaders run

MILKDROP_PRESET_VERSION	Warp stage	Composite stage
missing or < 200 (default 100)	fixed-function	fixed-function
200	PSVERSION (default 2)	PSVERSION
> 200 (MilkDrop writes 201)	PSVERSION_WARP (default 2)	PSVERSION_COMP (default 2)

A shader version of 0 means the classic fixed-function stage; anything above 0 enables your warp_/comp_ code. MilkDrop distinguishes 2 (ps_2_0), 3 (ps_2_x) and 4 (ps_3_0) when compiling. projectM only checks "greater than 0".

Of the 9,606 bundled presets, 1,506 have no version line at all and therefore run fixed-function stages, even if they contain shader code.

Shader version without shader code

With a version of 200 or more, PSVERSION_COMP > 0 and no comp_ lines, MilkDrop generates a composite shader that still applies gamma, video echo and the legacy filters. projectM substitutes a plain pass-through without gamma, so with the default fGammaAdj=2, the image is roughly half as bright. If you want the classic composite, set PSVERSION_COMP=0. If you want a shader, write one.

Code blocks

Block	Keys	Runs
Preset init	per_frame_init_1, per_frame_init_2, …	Once, at load
Per frame	per_frame_1, …	Once per frame
Per vertex	per_pixel_1, …	Once per warp-mesh vertex per frame
Custom wave N (0-3)	wave_N_init1, wave_N_per_frame1, wave_N_per_point1	Init once; per frame; per point
Custom shape N (0-3)	shape_N_init1, shape_N_per_frame1	Init once; per frame, once per instance
Shaders	warp_1, comp_1, …	On the GPU, per pixel

Wave and shape code keys have no underscore before the line number (wave_0_per_point1, not wave_0_per_point_1). A preset has at most four custom waves and four custom shapes.

Settings for waves and shapes use the wavecode_N_ and shapecode_N_ prefixes:

• Waves: enabled, samples, sep, bSpectrum, bUseDots, bDrawThick, bAdditive, scaling, smoothing, r, g, b, a.
• Shapes: enabled, sides, additive, thickOutline, textured, num_inst, x, y, rad, ang, tex_ang, tex_zoom, r g b a, r2 g2 b2 a2, border_r g b a.

Numbered lines and how they are joined

Both readers start at line 1 and stop at the first missing number. If you delete per_frame_7, everything from per_frame_8 onwards is silently ignored. MilkDrop also stops at 32,768 characters per block.

A leading backtick is stripped from every code line. MilkDrop's exporter adds one to shader lines so that leading spaces survive.

The two engines join the lines into one program differently:

• MilkDrop joins equation lines with no separator at all, then removes // and \\ comments to the end of each line (CState::StripLinefeedCharsAndComments, state.cpp:1526). Two lines a=1; and b=2; become a=1;b=2;; without the ; they would fuse into a=1b=2. A name split across two lines is glued back together.
• projectM joins lines with a newline, and its evaluator understands // and /* */ comments.

Real presets depend on MilkDrop's rule. 161.milk splits a variable name across lines:

per_frame_22=k1 =  is_
per_frame_23=beat*equal(index%2,0);

MilkDrop reads is_beat. Stock projectM sees two names and rejects the whole preset. ProjectM TV retries rejected code in MilkDrop's joined form, so it renders as on Windows.

Other legacy forms seen in bundled presets:

Form	Example	Meaning in MilkDrop
\\ comment	shape_3_per_frame18=/////// Planetary system \\\\\\\	Comment to end of line
Stray ; before )	shape_3_init176=index=index+1;);	NS-EEL reads it as a space
Lone .	y=if(c,.-.4,y);	The number 0

When code does not compile

MilkDrop never refuses a preset because of an equation error. It shows an error message for a few seconds, leaves out the block that failed, and runs the rest (CState::RecompileExpressions, state.cpp:1553):

• If per_frame_init fails, q1 to q32 start at zero.
• If a wave or shape init fails, its t1 to t8 start at zero.
• A failed per-frame, per-pixel or per-point block does not run.

projectM 4.2 fails the entire preset on any equation compile error. ProjectM TV follows MilkDrop: only a file that cannot be parsed at all fails to load. Each left-out block is logged as Preset code left out (<preset>): <reason> (line N, column M) (see Test and predict).

Portability

For presets that should also work in stock projectM: number lines without gaps, keep every token on one line, end every statement with ;, use // comments, write 0 rather than ., and avoid ;).