webapp/src/params.ts at 65ecc0383eaa1e9f3c5cac9a8b371456a9a70b75

simulated_instruments / cymbal2

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1// Parameter definitions for the cymbal2 model, mirroring cymbal2_defaults.m.

2// Unlike the sibling cymbal app there are no recomputation tiers: the

3// expensive stage is the time integration itself, and everything feeds it.

4// The render duration is not a parameter: it is

5// (strike_count - 1) / strike_rate_hz + tail_s, plus the first stroke's

6// travel time.

8export interface Cymbal2Params {

9 // Shell geometry

10 radius_m: number;

11 rise_m: number;

12 thickness_m: number;

13 // Material

14 youngs_modulus: number;

15 poisson_ratio: number;

16 density: number;

17 // Damping

18 sigma0: number;

19 sigma1: number;

20 // Support

21 washer_radius_m: number;

22 washer_stiffness: number;

23 washer_mass: number;

24 washer_damping: number;

25 support_clamped: boolean;

26 // Mallet head

27 head_radius_m: number;

28 head_mass_kg: number;

29 head_stiffness: number;

30 head_alpha: number;

31 // Mallet stick

32 stick_length_m: number;

33 stick_area_m2: number;

34 stick_youngs: number;

35 stick_density: number;

36 stick_inertia_m4: number;

37 stick_damping_rate: number;

38 n_beam: number;

39 // Grip

40 grip_clamped: boolean;

41 grip_spring: number;

42 // Strike gesture

43 strike_velocity: number;

44 strike_accel: number;

45 retract_accel: number;

46 strike_hold_ms: number;

47 strike_gap_m: number;

48 strike_r: number;

49 strike_theta_deg: number;

50 strike_count: number;

51 strike_rate_hz: number;

52 velocity_spread: number;

53 seed: number;

54 // Pickup

55 pickup_r: number;

56 pickup_theta_deg: number;

57 // Discretization

58 n_radial: number;

59 n_theta: number;

60 g_param: number;

61 phi_param: number;

62 // Rendering

63 sample_rate: number;

64 oversample: number;

65 tail_s: number;

66 pre_delay_ms: number;

67 normalize: boolean;

68 peak_dbfs: number;

69 full_scale_accel: number;

70 bit_depth: number;

71}

73export const DEFAULTS: Cymbal2Params = {

74 radius_m: 0.23,

75 rise_m: 0.04,

76 thickness_m: 0.001,

77 youngs_modulus: 1.1e11,

78 poisson_ratio: 0.33,

79 density: 8860.0,

80 sigma0: 1.34,

81 sigma1: 1.2e-3,

82 washer_radius_m: 0.029,

83 washer_stiffness: 1.65e5,

84 washer_mass: 0.0,

85 washer_damping: 0.0,

86 support_clamped: false,

87 head_radius_m: 0.025,

88 head_mass_kg: 0.028,

89 head_stiffness: 1.6e8,

90 head_alpha: 2.54,

91 stick_length_m: 0.39,

92 stick_area_m2: 1.43139e-4,

93 stick_youngs: 8.8e9,

94 stick_density: 400.0,

95 stick_inertia_m4: 1.63044e-9,

96 stick_damping_rate: 10.0,

97 n_beam: 20,

98 grip_clamped: false,

99 grip_spring: 140.0,

100 strike_velocity: 4.0,

101 strike_accel: 250.0,

102 retract_accel: 2500.0,

103 strike_hold_ms: 0.5,

104 strike_gap_m: -1,

105 strike_r: 0.6,

106 strike_theta_deg: 180.0,

107 strike_count: 1,

108 strike_rate_hz: 4.0,

109 velocity_spread: 0.0,

110 seed: 1,

111 pickup_r: 0.6,

112 pickup_theta_deg: 0.0,

113 n_radial: 24,

114 n_theta: 60,

115 g_param: 0.2498,

116 phi_param: 0.7,

117 sample_rate: 48000,

118 oversample: 2,

119 tail_s: 6.0,

120 pre_delay_ms: 3.0,

121 normalize: true,

122 peak_dbfs: -3.0,

123 full_scale_accel: 4.0e4,

124 bit_depth: 24,

125};

126

127// Keys that determine the linear mode table (cymbal2_modes); the cheap modes

128// stage is cached on these.

129export const MODES_KEYS: (keyof Cymbal2Params)[] = [

130 'radius_m', 'rise_m', 'thickness_m',

131 'youngs_modulus', 'poisson_ratio', 'density',

132 'washer_radius_m', 'washer_stiffness', 'support_clamped',

133 'n_radial', 'n_theta',

134];

135

136export interface ParamSpec {

137 key: keyof Cymbal2Params;

138 label: string;

139 unit?: string;

140 min: number;

141 max: number;

142 step?: number;

143 log?: boolean;

144 integer?: boolean;

145 help?: string;

146}

147

148export interface ParamGroup {

149 name: string;

150 specs: ParamSpec[];

151}

152

153export const PARAM_GROUPS: ParamGroup[] = [

154 {

155 name: 'Stroke',

156 specs: [

157 { key: 'strike_velocity', label: 'Hand speed', unit: 'm/s', min: 0.25, max: 7.0, step: 0.05, help: 'Peak speed of the hand. The compliant stick whips, so the tip arrives about 1.3x faster. 0.5 taps, 2 begins to wash, 4 and up crash. Above about 7 the explicit nonlinear integration diverges, which is also where the shallow-shell physics stops being valid; the renderer reports it rather than emitting garbage.' },

158 { key: 'strike_r', label: 'Contact position', min: 0.05, max: 0.99, step: 0.005, help: 'Radial fraction from the washer (0) to the rim (1); draggable on the cross-section above. Near the rim drives the high nodal-diameter modes; near the washer rings sparser.' },

159 { key: 'strike_accel', label: 'Downstroke accel', unit: 'm/s²', min: 50, max: 4000, log: true, help: 'How hard the arm accelerates. Faster strokes give the compliant stick less time to follow, so the tip whips more.' },

160 { key: 'retract_accel', label: 'Retract accel', unit: 'm/s²', min: 200, max: 20000, log: true, help: 'The wrist snap pulling the stick back after contact. Too slow and the stick shoves the wobbling shell and re-hits it.' },

161 { key: 'strike_hold_ms', label: 'Hold', unit: 'ms', min: 0, max: 20, step: 0.5, help: 'Dwell between first contact and the retract. Long holds choke the shell against the head.' },

162 ],

163 },

164 {

165 name: 'Repeats',

166 specs: [

167 { key: 'strike_count', label: 'Strokes', min: 1, max: 16, step: 1, integer: true, help: 'The hand returns to rest between strokes, which the paper\'s constant-acceleration hand cannot do.' },

168 { key: 'strike_rate_hz', label: 'Rate', unit: 'Hz', min: 0.5, max: 12, step: 0.25, help: 'Strokes per second. A stroke whose predecessor has not finished retracting is skipped.' },

169 { key: 'velocity_spread', label: 'Velocity spread', min: 0, max: 0.7, step: 0.01, help: 'Relative scatter of the per-stroke hand speeds.' },

170 { key: 'seed', label: 'Random seed', min: 1, max: 9999, step: 1, integer: true, help: 'Redraws the velocity scatter; the same seed always reproduces it.' },

171 ],

172 },

173 {

174 name: 'Support (washer)',

175 specs: [

176 { key: 'washer_stiffness', label: 'Washer stiffness', unit: 'N/m/m', min: 1e4, max: 1e7, log: true, help: 'Spring per unit length of the mounting circle; 1.65e5 is the paper\'s measured felt washer. It sets the bounce (about 13 Hz) and tilt (about 4 Hz) of the whole shell on its mount, and through the boundary condition the low audible modes too.' },

177 { key: 'washer_damping', label: 'Washer damping', unit: 'N s/m/m', min: 0, max: 500, step: 1, help: 'Dashpot per unit length alongside the spring. The paper sets 0; a real felt sleeve has some.' },

178 { key: 'washer_mass', label: 'Washer mass', unit: 'kg/m', min: 0, max: 1, step: 0.005, help: 'Mass per unit length moving with the mounting circle. The paper sets 0.' },

179 { key: 'washer_radius_m', label: 'Washer radius', unit: 'm', min: 0.015, max: 0.06, step: 0.001, help: 'Radius of the mounting circle. The grid needs it above roughly 3 radial spacings; the builder refuses configurations it cannot resolve.' },

180 ],

181 },

182 {

183 name: 'Mallet',

184 specs: [

185 { key: 'head_mass_kg', label: 'Head mass', unit: 'kg', min: 0.002, max: 0.2, log: true, help: 'The 28 g head of the paper\'s measured mallet. Heavier darkens and lengthens the contact.' },

186 { key: 'head_stiffness', label: 'Head stiffness', unit: 'N m⁻ᵅ', min: 1e6, max: 1e11, log: true, help: 'Coefficient of the Hertz-type contact f = K delta^alpha. Softer rolls the attack off; a wood tip is orders of magnitude stiffer than felt.' },

187 { key: 'head_alpha', label: 'Contact exponent', min: 1.2, max: 3.5, step: 0.02, help: 'Hertz theory gives 1.5 for a sphere on a plate; the paper\'s measured mallet is 2.54, felt being strongly hardening.' },

188 { key: 'head_radius_m', label: 'Head radius', unit: 'm', min: 0.005, max: 0.05, step: 0.001 },

189 ],

190 },

191 {

192 name: 'Stick and grip',

193 specs: [

194 { key: 'grip_spring', label: 'Grip stiffness', unit: 'N m/rad', min: 10, max: 5000, log: true, help: 'Rotational spring of the loose grip. Softer lets the stick pivot freely and whip; the audible effect is on the attack, as the paper\'s grip-tightness experiment found.' },

195 { key: 'stick_youngs', label: 'Stick modulus', unit: 'Pa', min: 1e9, max: 1e11, log: true, help: 'Wood is about 9e9. A stiffer stick follows the hand faster and doubles the contact peaks differently.' },

196 { key: 'stick_length_m', label: 'Stick length', unit: 'm', min: 0.2, max: 0.6, step: 0.005 },

197 { key: 'stick_density', label: 'Stick density', unit: 'kg/m³', min: 200, max: 1200, step: 10 },

198 { key: 'stick_damping_rate', label: 'Stick damping', unit: 's⁻¹', min: 0, max: 100, step: 1, help: 'Mass-proportional damping of the stick; the paper uses 10.' },

199 ],

200 },

201 {

202 name: 'Shell geometry',

203 specs: [

204 { key: 'radius_m', label: 'Radius', unit: 'm', min: 0.12, max: 0.35, step: 0.001, help: '0.23 is the paper\'s 18-inch crash. Mode frequencies scale roughly as thickness / radius².' },

205 { key: 'rise_m', label: 'Rise', unit: 'm', min: 0.005, max: 0.09, step: 0.001, help: 'Height of the cap; sets the radius of curvature Rs = a²/(2 rise). More curvature stiffens the low modes through the membrane coupling and raises the ring frequency.' },

206 { key: 'thickness_m', label: 'Thickness', unit: 'm', min: 0.0004, max: 0.003, step: 0.00005, help: 'Uniform; the shallow-shell formulation cannot carry a taper. Thin crashes, thick rides. The nonlinearity strengthens as displacement over thickness.' },

207 ],

208 },

209 {

210 name: 'Material and damping',

211 specs: [

212 { key: 'density', label: 'Density', unit: 'kg/m³', min: 2000, max: 12000, log: true, help: 'The paper\'s measured bronze is 8860.' },

213 { key: 'youngs_modulus', label: "Young's modulus", unit: 'Pa', min: 3e10, max: 3e11, log: true },

214 { key: 'poisson_ratio', label: 'Poisson ratio', min: 0.0, max: 0.45, step: 0.01 },

215 { key: 'sigma0', label: 'Damping σ₀', unit: 's⁻¹', min: 0.05, max: 10, log: true, help: 'Frequency-independent decay rate: T60 = 6.91 / (2 σ₀) ... more precisely 3 ln10 / σ₀ at the bottom of the band. The paper fits 1.34.' },

216 { key: 'sigma1', label: 'Damping σ₁', min: 0, max: 0.02, step: 0.0001, help: 'High-frequency damping, growing as the squared wavenumber. The paper fits 1.2e-3.' },

217 ],

218 },

219 {

220 name: 'Pickup',

221 specs: [

222 { key: 'pickup_r', label: 'Pickup position', min: 0.05, max: 0.99, step: 0.005, help: 'Radial fraction of the pickup point, draggable on the cross-section. The output is the shell\'s normal acceleration there: a contact pickup, not a microphone.' },

223 { key: 'pickup_theta_deg', label: 'Pickup azimuth', unit: '°', min: 0, max: 359, step: 1, help: 'The strike is at 180°. On top of it you hear the contact hardest.' },

224 ],

225 },

226 {

227 name: 'Output',

228 specs: [

229 { key: 'tail_s', label: 'Tail', unit: 's', min: 0.5, max: 12.0, step: 0.1, help: 'Ring time rendered after the last stroke. The low modes carry T60 near 5 s at the default damping.' },

230 { key: 'pre_delay_ms', label: 'Pre-delay', unit: 'ms', min: 0, max: 50, step: 0.5 },

231 { key: 'peak_dbfs', label: 'Peak level', unit: 'dBFS', min: -24, max: 0, step: 0.5, help: 'Used when normalize is on.' },

232 { key: 'full_scale_accel', label: 'Full scale', unit: 'm/s²', min: 1e2, max: 1e6, log: true, help: 'Used when normalize is off: this acceleration maps to 0 dBFS.' },

233 ],

234 },

235 {

236 name: 'Advanced / quality',

237 specs: [

238 { key: 'n_radial', label: 'Radial intervals', min: 20, max: 48, step: 1, integer: true, help: 'The paper\'s grid uses 24. The washer circle needs about 3 radial spacings inside it; too-coarse grids are refused. Cost is roughly linear.' },

239 { key: 'n_theta', label: 'Azimuthal points', min: 24, max: 120, step: 2, integer: true, help: 'The paper uses 60. Sets the highest nodal-diameter order carried; the crash\'s top octaves live there, and hard strokes need the full ladder or the cascade piles up at the cutoff and diverges. Cost is roughly linear.' },

240 { key: 'oversample', label: 'Oversample', min: 1, max: 4, step: 1, integer: true, help: 'Simulation rate multiple of the output rate. 2 matches the paper\'s 88.2 kHz; hard strokes need it for stability of the explicit nonlinearity.' },

241 { key: 'g_param', label: 'Scheme g', min: 0.24, max: 0.3, step: 0.0002, help: 'Free parameter of the implicit shell scheme; the paper uses 0.2498. At 0.25 and above the linear part is unconditionally stable.' },

242 { key: 'phi_param', label: 'Scheme φ', min: 0.5, max: 1.0, step: 0.01, help: 'Implicit weight of the washer and beam schemes.' },

243 { key: 'n_beam', label: 'Beam elements', min: 8, max: 40, step: 1, integer: true },

244 { key: 'strike_gap_m', label: 'Rest clearance', unit: 'm', min: -1, max: 0.5, step: 0.005, help: 'Head-to-shell clearance at rest. Nonpositive sizes it to the stroke so contact arrives just after full speed, which keeps the tip whip consistent.' },

245 ],

246 },

247];

248

249const STORAGE_KEY = 'cymbal2-webapp-params-v1';

250

251export function loadParams(): Cymbal2Params {

252 try {

253 const raw = localStorage.getItem(STORAGE_KEY);

254 if (!raw) return { ...DEFAULTS };

255 const parsed = JSON.parse(raw);

256 const out = { ...DEFAULTS };