Preset JSON Format

Preset JSON files in the data folder define the parameters used by the shell-building pipeline. Each preset describes the growth path, shell surface, optional chamber septa, optional siphuncle, and rendering settings for one shell form.

Not every parameter is used by every shell. Some parameters apply only to particular growth modes, shell families, or optional features.

Top-Level Metadata

Parameter	Purpose
name	Human-readable name for the preset.
description	Short description of the shell form and its main modelling features.
geometry	Broad geometry category used to describe the preset, such as log-spiral, centreline-conical, or conical-helix.
form	Morphological form label, such as planispiral, straight, curved, high-spired, or flared.
family	Biological or modelling family label, such as coiled-cephalopod, straight-shelled-cephalopod, or gastropod.

growth

The growth section defines the path followed by the aperture as the shell is generated.

Parameter	Purpose
mode	Selects the growth-path model. Current modes include log_spiral, orthocone, cyrtocone, and conical_helix.
a	Initial scale parameter for logarithmic spiral and conical helix growth.
b	Expansion parameter for logarithmic spiral and conical helix growth. Larger values usually increase shell expansion more quickly.
turns	Number of spiral or helical turns to generate.
points	Number of sampled growth positions. Higher values produce smoother meshes but increase render cost.
aperture_mode	Controls how aperture size is calculated. Common values are proportional and abutting.
aperture_width_multiplier	Scales aperture width relative to the growth path size. Used by proportional and centreline growth modes.
aperture_height_multiplier	Scales aperture height relative to the growth path size. Used by proportional and centreline growth modes.
abutment_scale	Controls aperture size for abutting coiled shells, helping adjacent whorls touch or overlap.
abutment_height_ratio	Controls aperture height relative to abutting aperture width.
length	Axial length for centreline shells such as orthocones and cyrtocones.
initial_radius	Starting aperture radius for centreline shells.
growth_rate	Rate at which centreline shell radius changes along the axis.
curvature	Curvature applied to centreline shells. null gives a straight orthocone-like axis; non-zero values curve the shell into a cyrtocone-like form.
taper_mode	Controls how centreline shell radius changes along the shell. For example, linear gives a linear taper.
spire_height	Height of the conical helix spire. Used by conical_helix growth.
cone_taper	Controls how strongly a conical helix narrows toward the apex.

shell

The shell section controls aperture sweep geometry, surface ornamentation, the final aperture lip, and wall thickness.

Parameter	Purpose
z_scale	Adds vertical rise to the shell when no explicit z_path is generated. Useful for raised or open spiral forms.
automatic_z_path	When true, derives vertical rise automatically from aperture height and whorl abutment. Used for high-spired forms such as Turritella-like shells.
whorl_abutment	Controls automatic spacing between successive whorls when automatic_z_path is enabled. Lower values increase overlap; higher values increase separation.
aperture_points	Number of vertices around each aperture ring. Higher values make rounder apertures but increase mesh size.
aperture_tilt	Shears the aperture so one side sits higher than the other. Useful for inclined high-spired forms.
ribbing_enabled	Enables or disables geometric ribbing.
ribbing_amplitude	Strength of ribbing modulation. Larger values create stronger raised ribs or deeper annulations.
ribbing_frequency	Frequency of ribs along the growth path. Higher values produce more closely spaced ribs. In segmented mode this is overridden when segment_to_septum_ratio is active.
ribbing_mode	Rib profile. sinusoidal preserves the original smooth ribbing; segmented creates broad annular segments separated by grooves.
segment_to_septum_ratio	Optional segmented-mode control that locks annulations to chamber spacing when chamber septa are enabled. 1.0 gives one ring per chamber, 2.0 gives two rings per chamber, and 0.5 gives one ring every two chambers.
ribbing_groove_width	Fraction of each segmented rib cycle occupied by the groove. Larger values make wider grooves.
ribbing_groove_depth	Relative depth of segmented grooves. Larger values make grooves cut more deeply into the raised annular band.
lip_enabled	Enables or disables final aperture flare.
lip_start	Growth fraction where the final lip flare begins. For example, 0.90 starts the lip during the final 10 percent of growth.
lip_strength	Maximum enlargement of the final aperture lip.
lip_power	Shape exponent controlling how gradually or abruptly the lip flare develops.
wall_enabled	Enables or disables the inner shell wall surface.
wall_thickness	Inset distance used to create the inner shell wall.
inner_surface_colour_shift	Colour adjustment applied to the inner shell surface. Negative values darken the inner wall.

chambers

The chambers section controls internal septa. These parameters are used only when chamber generation is enabled.

Parameter	Purpose
enabled	Enables or disables chamber septa.
chamber_spacing	Distance between successive septa along the chamber-placement coordinate. For coiled shells this is based on growth angle; for orthocones and cyrtocones this is interpreted along the shell axis.
septum_rings	Number of nested rings used to build each septum surface. Higher values give smoother septa.
septum_depth	Strength of septum concavity. Larger values make septa more deeply curved inward.

siphuncle

The siphuncle section controls the simplified tube running through chambered cephalopod shells.

Parameter	Purpose
enabled	Enables or disables siphuncle generation.
siphuncle_radius	Base radius of the siphuncle tube.
siphuncle_taper_enabled	Enables or disables tapering of the siphuncle radius along the shell.
siphuncle_taper_power	Shape exponent controlling the taper curve when siphuncle tapering is enabled.
siphuncle_min_radius	Minimum siphuncle radius when tapering is enabled.
siphuncle_max_radius	Maximum siphuncle radius when tapering is enabled.
siphuncle_offset	Offset of the siphuncle from the aperture centre. Higher values place it closer to the shell wall.
tube_points	Number of vertices around each siphuncle tube ring. Higher values make a rounder tube.
siphuncle_end_fraction	Fraction of shell growth over which to generate the siphuncle. This usually stops the siphuncle before the final body chamber or aperture lip.
include_terminal_ring	Controls whether a final terminal siphuncle ring is included.
fixed_offset_angle	Optional fixed angular position for the siphuncle offset. null allows the offset to follow shell growth orientation.

plotting

The plotting section contains render settings. Presets usually define separate opaque and transparent render configurations using the same parameter names.

Parameter	Purpose
opaque	Render settings for the opaque shell view.
transparent	Render settings for the transparent shell view.

Plotting View Settings

Parameter	Purpose
enabled	Enables or disables this render configuration.
title	Title shown on the rendered Plotly figure.
shell_opacity	Opacity of the shell mesh. 1.0 is fully opaque; lower values make the shell translucent.
septa_opacity	Opacity of chamber septa.
siphuncle_opacity	Opacity of the siphuncle.
width	Output image or figure width in pixels.
height	Output image or figure height in pixels.
hide_axes	Hides or shows the 3D axes.
show_wireframe	Shows or hides wireframe-style mesh edges when supported by the plotting path.
viewpoint	Named camera viewpoint, such as iso, top, aperture, or presentation.
zoom	Camera zoom factor. Smaller values zoom in; larger values zoom out.