When you start with a portrait and search for a pure form,
a clear volume, through successive eliminations, you arrive
inevitably at the egg. Likewise, starting with the egg and
following the same process in reverse, one finishes with
the portrait.
PABLO PICASSO
Easter is coming and what better time to talk about eggs!
During my recent mathematical explorations of natural shapes and forms, my attention has been caught by the shape of birds’ eggs. In the exciting book by J. Adams, A Mathematical Walk in Nature [1], you can find a short review of the different mathematical modeling approaches to describe the shape of an egg. Among them, the geometrical one by Baker [2] is revealed as one of the most versatile as it can accurately reproduce the shapes of a large variety of bird eggs [2]. More recently, the model was used to perform a systematic and comparative study of the shape of bird eggs. This study, published in Science magazine [3], a two-dimensional morphological space defined by the parameters of Baker’s equation, has been used to show the diversity of the shape of 1400 species of birds. Combining this information with a mechanical model and phylogenetics information, the authors have shown that egg shape correlates with flight ability on broad taxonomic scales. They concluded that adaptations for flight may have been critical drivers of egg-shape variation in birds [3].
Baker’s equation is based on a fundamental transformation from projective geometry. This mathematical description generates so-called ‘‘path curves’’ resembling natural shapes such as eggs, buds, and embryos. This model was initially developed by L. Edwards [4] based on the previous idea of other mathematicians. The derivation details can be in the referenced publications, and here I talk about its application. The following expression gives the equation:
where 
An example of a European bird that makes eggs with a low value of A and E is the European blue bee-eater.
As the parameter 
An example of a bird egg with a low value of A and a larger value of E is, for example, the one from the Great Bustard bird (see figure below
If the value of the parameter 
An example of bird egg with large value of A and larger value of E is, for example, the one from the Least sandpiper (see figure below).
It is possible to calculate the volume and the surface of the solid of the revolution generated by Beker’s equation. If L is the average length (L) of the egg’s main axis, then the volume of revolution is
and the surface are
The egg models in this blog have been generated using a tcl/tk program that I have written for the occasion. The program has a database of more than 300 European birds. The value of A and E in the database has been taken from the supplementary data of the Stoddard et al. paper [3] and the common bird names from the IOC word list of bird names. The program’s current version can calculate the egg’s volume and surface by integrating the revolution solid using the Simpson 1/3 rule.
What about chocolate egg shapes? Well, for the moment, shall we enjoy eating them!
BUONA PASQUA – HAPPY EASTER – FROHE OSTERN
and stay tuned …
REFERENCES
- J. A. Adams. A Mathematical Nature Walk. Princeton University Press. 2011.
- D. E. Baker. A Geometric Method for Determining Shape of Bird Eggs. The Auk 119(4):1179–1186, 2002.
- M. C. Stoddard et al. Avian egg shape: Form, function, and evolution.Science 356, 1249–1254 (2017).
- L. Edwards. The Vortex of Life: Nature’s Patterns in Space and Time. Floris Books, 2nd Revised edition edition (4 May 2006).
APPENDIX
Program in TCL/TK language used to generate the figures in this article. You are welcome to use it but please read the statement in the About section of my blog.
#! /bin/sh
# the next line restarts using wish \
exec wish "$0" "$@"
#
#########################################################################
# PROGRAM: Eggshape
#
# This program perform the calculation of the 2d profiel shape of
# bird eggs using the Baker equation
# y = T*(1+x)^(1/1+lam)(1-x)^(la/(1+lam)).
# (D. E. Baker. The Auk 119(4):1179â1186, 2002.)
# The shape of the curve is defined by the two parameters
# asymmetry : A=lam-1,
# ellipticity: E=1/T-1,
#
# The program is provided with a small database of selected European birds
# with parameters (A, and E) obtained from the paper:
# M. C. Stoddard et al. Science 356, 1249â1254 (2017).
# ######################################################################
# DEVELOPED BY
# (c) Danilo Roccatano 2018
# #
# VERSION: 1.0
# #
#########################################################################
#
# root is the parent window for this user interface
package require Tk
wm title . ""
tk_setPalette cyan3
# Define some variables
# this treats "." as a special case
set root "."
set base ""
set maxX 500
set maxY 500
set width 0
set height 0
set midX 0
set midY 0
set rmin -5.0
set rmax 5.0
set ymax 2.
set ymin -2.
set T 1.0
set np 300
set lam 1.0
set pA 0.0
set pE 0.0
set pL 1.0
set vol 0.0
set surf 0.0
set nc 0
set ex1 0.5
set ex2 0.5
set COLORS { black gray75 gray50 white darkred red DarkMagenta
magenta green4 green Gold4 yellow navy blue turquoise4 cyan
}
set nCOLORS [llength $COLORS]
set PARAM {
" 0.1636 0.3456 1.8400" " 0.2897 0.5311 4.3587" " 0.1519 0.3363 1.6534" " 0.0769 0.3573 4.8971" \
" 0.0679 0.4191 6.0883" " 0.2182 0.4966 4.8785" " 0.4331 0.6112 4.9874" " 0.0924 0.2442 3.5432" \
" 0.1486 0.3406 1.6513" " 0.1706 0.4153 2.8629" " 0.2586 0.4590 5.9276" " 0.2121 0.3807 4.0492" \
" 0.1938 0.3483 2.6981" " 0.1117 0.3466 2.8217" " 0.1611 0.3540 4.0471" " 0.1398 0.3118 4.2910" \
" 0.1265 0.3308 1.9853" " 0.1291 0.4044 6.0698" " 0.0933 0.6039 9.1690" " 0.1207 0.2856 1.6177" \
" 0.1730 0.4024 5.1333" " 0.2199 0.4778 5.8653" " 0.1145 0.3064 5.6094" " 0.1430 0.3602 1.9425" \
" 0.1612 0.6657 9.7472" " 0.2706 0.4178 3.4035" " 0.0700 0.3476 8.9076" " 0.1708 0.4462 2.4311" \
" 0.0413 0.4703 4.7640" " 0.0713 0.3530 2.8341" " 0.1013 0.2954 1.9652" " 0.1356 0.3123 1.8190" \
" 0.1063 0.4736 4.3948" " 0.4287 0.5156 5.4411" " 0.2064 0.6456 7.9108" " 0.1883 0.3342 1.6722" \
" 0.2013 0.4230 3.0368" " 0.1449 0.3712 1.9325" " 0.1766 0.3422 1.7096" " 0.2146 0.4097 1.5982" \
" 0.0181 0.1453 2.2946" " 0.1789 0.3115 1.7843" " 0.0881 0.3517 4.5562" " 0.1575 0.3635 2.1076" \
" 0.2111 0.4330 2.4754" " 0.1788 0.3840 4.6936" " 0.1260 0.2847 5.9398" " 0.2204 0.3594 1.9553" \
" 0.1340 0.5066 6.9952" " 0.2166 0.4745 4.8174" " 0.3473 0.3799 3.0342" " 0.1219 0.3583 2.6591" \
" 0.4336 0.6453 7.8649" " 0.1011 0.4011 4.9665" " 0.1621 0.4149 2.0049" " 0.2208 0.3937 4.0903" \
" 0.1202 0.5178 7.7142" " 0.2068 0.3951 1.6354" " 0.1481 0.3984 5.7557" " 0.2035 0.4238 4.2014" \
" 0.1515 0.3532 1.9394" " 0.1237 0.3123 1.4878" " 0.1237 0.3092 2.0214" " 0.1694 0.3551 2.0225" \
" 0.2276 0.3787 2.2665" " 0.0704 0.2610 5.6364" " 0.2244 0.4991 5.5796" " 0.2473 0.5875 10.1558" \
" 0.2173 0.4312 5.7221" " 0.1075 0.2936 4.0485" " 0.0785 0.2403 2.1945" " 0.2528 0.4691 5.1864" \
" 0.1964 0.2980 2.9223" " 0.2141 0.4863 2.1700" " 0.2068 0.5117 6.5706" " 0.1935 0.4223 2.9421" \
" 0.2508 0.5120 2.4391" " 0.2157 0.4011 4.1283" " 0.0731 0.3420 1.3861" " 0.2019 0.4985 3.8930" \
" 0.2370 0.3763 3.5900" " 0.2505 0.4659 5.3474" " 0.1753 0.4578 2.2639" " 0.3940 0.4537 6.6281" \
" 0.2053 0.4100 2.2884" " 0.2819 0.4683 2.5986" " 0.2275 0.5119 4.0186" " 0.3971 0.4786 3.4468" \
" 0.1670 0.3401 1.9334" " 0.0937 0.2717 5.8952" " 0.0560 0.3363 3.2469" " 0.0728 0.3321 7.0769" \
" 0.1654 0.4967 7.3276" " 0.0384 0.1732 2.5503" " 0.0632 0.3883 3.0569" " 0.2016 0.4608 2.4960" \
" 0.0871 0.3170 1.5199" " 0.1920 0.3988 2.9301" " 0.2561 0.4528 4.3439" " 0.1258 0.3374 2.2316" \
" 0.2646 0.4316 5.1410" " 0.0729 0.3895 5.4852" " 0.1636 0.6319 7.9350" " 0.1655 0.3418 1.9098" \
" 0.1922 0.6018 10.6605" " 0.2681 0.4601 7.3257" " 0.1072 0.4256 5.0908" " 0.1518 0.3274 1.3981" \
" 0.1192 0.3058 7.7318" " 0.2662 0.4650 3.1993" " 0.4107 0.5328 5.1358" " 0.0966 0.3842 6.0448" \
" 0.0674 0.4558 6.5418" " 0.1114 0.3186 5.9863" " 0.1257 0.3610 1.7474" " 0.0793 0.4923 8.4211" \
" 0.0995 0.4382 5.0450" " 0.1660 0.6084 8.5517" " 0.1620 0.4227 2.2170" " 0.2747 0.4073 6.7837" \
" 0.1550 0.3224 1.7510" " 0.2803 0.4860 7.8012" " 0.1712 0.5955 8.8469" " 0.2014 0.4624 3.2817" \
" 0.1502 0.3648 1.9337" " 0.1099 0.3489 2.3090" " 0.0753 0.4232 6.0670" " 0.2448 0.3810 3.6486" \
" 0.4142 0.4796 3.0472" " 0.1830 0.3411 1.9338" " 0.1736 0.4360 2.3101" " 0.3232 0.5250 5.3752" \
" 0.2306 0.3719 2.8684" " 0.1322 0.3838 10.1228" " 0.4502 0.6791 8.1741" " 0.1233 0.2796 5.9904" \
" 0.1180 0.3655 5.6550" " 0.1872 0.4567 2.4508" " 0.0436 0.2664 3.9818" " 0.1078 0.2998 4.6828" \
" 0.1509 0.3589 2.2312" " 0.2685 0.4755 7.2042" " 0.1022 0.2116 3.9517" " 0.1435 0.3149 1.8003" \
" 0.1240 0.4339 2.5969" " 0.1693 0.4178 2.1393" " 0.3048 0.4992 5.2708" " 0.2536 0.5312 7.2188" \
" 0.1936 0.4469 1.8936" " 0.1276 0.3557 1.8907" " 0.1648 0.3566 2.0814" " 0.1898 0.4273 3.3777" \
" 0.1704 0.4179 3.2388" " 0.2566 0.3930 3.1152" " 0.1750 0.5281 7.3883" " 0.2552 0.3851 5.5084" \
" 0.1270 0.2896 5.2158" " 0.1631 0.3921 2.0766" " 0.3433 0.4373 4.5780" " 0.2444 0.4174 5.4455" \
" 0.0626 0.3483 3.1600" " 0.0394 0.3307 3.1788" " 0.4847 0.5026 2.9011" " 0.2393 0.4749 6.8727" \
" 0.0999 0.4449 5.6243" " 0.4213 0.4928 4.0009" " 0.1647 0.4020 4.6032" " 0.0733 0.3355 3.6788" \
" 0.0661 0.3489 2.1656" " 0.0831 0.4704 3.7323" " 0.0385 0.3898 3.7977" " 0.2000 0.3722 4.3342" \
" 0.3302 0.4210 2.9137" " 0.0437 0.2482 4.0689" " 0.1272 0.3962 5.2295" " 0.2764 0.4564 5.5264" \
" 0.1346 0.3397 1.4509" " 0.1507 0.4798 6.9727" " 0.1739 0.4544 3.4812" " 0.0980 0.4012 5.7726" \
" 0.1952 0.4854 6.1967" " 0.0453 0.3205 1.5182" " 0.1421 0.3781 1.8426" " 0.1727 0.3820 1.9812" \
" 0.1129 0.3755 1.8011" " 0.1012 0.2717 3.9778" " 0.1740 0.4116 3.0644" " 0.1548 0.4251 4.4020" \
" 0.1128 0.3173 1.9154" " 0.0935 0.5440 11.4329" " 0.0980 0.4089 5.2569" " 0.1381 0.3555 2.4496" \
" 0.2040 0.4651 2.3117" " 0.0936 0.2777 1.9139" " 0.1105 0.4458 3.4690" " 0.1104 0.2708 1.8447" \
" 0.2301 0.4354 5.7429" " 0.1690 0.3578 1.5899" " 0.4288 0.4514 3.7690" " 0.1551 0.4935 1.5784" \
" 0.1175 0.2855 5.3360" " 0.1632 0.2604 4.2325" " 0.1609 0.3381 1.8467" " 0.0444 0.2753 2.9947" \
" 0.0860 0.2659 1.9534" " 0.0985 0.4591 4.3253" " 0.0285 0.4855 4.6293" " 0.1121 0.5340 8.3231" \
" 0.1079 0.4264 5.5042" " 0.2115 0.3634 6.2088" " 0.1395 0.3422 3.2323" " 0.2815 0.4829 6.3065" \
" 0.0875 0.3089 5.3435" " 0.1149 0.3732 5.2614" " 0.1403 0.3239 1.5479" " 0.2355 0.5033 4.7772" \
" 0.2880 0.5818 7.5757" " 0.1681 0.4001 2.1880" " 0.1625 0.3934 4.3524" " 0.1618 0.3788 2.2564" \
" 0.1235 0.4837 6.5329" " 0.1420 0.3060 1.5993" " 0.1917 0.4367 2.0757" " 0.1179 0.4951 6.3122" \
" 0.2113 0.4077 5.4057" " 0.1229 0.5738 5.6156" " 0.0770 0.3912 3.1095" " 0.3441 0.4578 3.0190" \
" 0.1132 0.4513 2.1730" " 0.2051 0.6573 7.2179" " 0.3984 0.4099 4.2849" " 0.1867 0.3536 2.7118" \
" 0.1758 0.3581 1.9238" " 0.1280 0.3826 1.8031" " 0.1499 0.3781 2.0967" " 0.1812 0.3863 2.9527" \
" 0.2452 0.4527 6.0373" " 0.0447 0.4049 5.5571" " 0.3354 0.4179 3.4851" " 0.1126 0.2689 1.9635" \
" 0.0623 0.3308 3.8068" " 0.1873 0.3837 3.8002" " 0.1679 0.3798 2.4202" " 0.2282 0.5707 3.2128" \
" 0.2341 0.4152 4.1273" " 0.0988 0.2700 5.7285" " 0.0802 0.3658 6.2467" " 0.4270 0.5061 4.3012" \
" 0.1102 0.3386 2.3901" " 0.2552 0.4106 4.4835" " 0.1865 0.4022 1.7483" " 0.2337 0.6112 7.8053" \
" 0.0743 0.3555 1.7890" " 0.1854 0.3838 2.2215" " 0.0898 0.4481 6.2056" " 0.0653 0.2517 3.0175" \
" 0.1587 0.3662 1.7430" " 0.3195 0.4628 3.3488" " 0.1936 0.7050 6.6986" " 0.1542 0.3826 2.1190" \
" 0.3291 0.4245 3.9478" " 0.0661 0.2772 4.0137" " 0.0976 0.4350 5.5683" " 0.1929 0.4492 3.0891" \
" 0.2951 0.6100 3.2005" " 0.2268 0.3613 1.7248" " 0.1488 0.3408 1.6882" " 0.2211 0.4560 2.3513" \
" 0.1103 0.3141 1.9360" " 0.1176 0.5360 4.4575" " 0.2410 0.4097 5.4963" " 0.3219 0.4563 3.9769" \
" 0.1972 0.4048 2.2715" " 0.1309 0.3258 1.9919" " 0.1610 0.3278 2.6754" " 0.2401 0.4734 5.1725" \
" 0.1522 0.4208 3.1632" " 0.0808 0.2391 4.0355" " 0.1776 0.4319 3.3752" " 0.2261 0.4186 1.8910" \
" 0.3112 0.3841 3.1437" " 0.0295 0.2923 3.6921" " 0.1611 0.3358 4.9116" " 0.0622 0.3166 2.8192" \
" 0.1744 0.3748 2.2639" " 0.1487 0.3553 2.2793" " 0.2226 0.4358 1.9450" " 0.1580 0.3432 1.6600" \
" 0.1715 0.3847 2.0899" " 0.0905 0.3759 4.5389" " 0.1475 0.3024 1.5931" " 0.1333 0.2656 2.2915" \
" 0.1643 0.4065 2.7919" " 0.1375 0.3460 2.0044" " 0.1506 0.3602 1.9217" " 0.3225 0.4119 4.4447" \
" 0.1403 0.3670 2.2671" " 0.1715 0.4803 7.1403" " 0.1925 0.6200 13.6912" " 0.1657 0.3622 2.0965" \
" 0.3913 0.4656 5.7441" " 0.0651 0.4380 7.6432" " 0.1633 0.3470 1.9996" " 0.2200 0.6530 8.6519" \
" 0.1462 0.3542 2.1499" " 0.1011 0.3721 3.6912" " 0.1009 0.3770 5.0639" " 0.1382 0.5313 7.5785" \
" 0.1394 0.5508 2.2989" " 0.1349 0.2862 7.8854" " 0.1427 0.3483 2.0902" " 0.1400 0.3286 1.7975" \
" 0.1225 0.5273 11.6695" " 0.1109 0.3930 5.3517" " 0.3971 0.4308 5.3917" " 0.1188 0.2981 1.5044" \
" 0.1439 0.3748 2.2050" " 0.0654 0.4041 4.0881" " 0.1433 0.3865 2.5463" " 0.1347 0.3131 1.5944" \
" 0.2332 0.2904 4.2483" " 0.1130 0.3484 2.0917" " 0.0410 0.3201 3.1167" " 0.1766 0.4655 2.6237" \
" 0.1593 0.3466 1.7847" " 0.1392 0.3311 2.0694" " 0.1299 0.3227 1.7420"
}
set CNAMES {
"Acadian flycatcher " "Aleutian tern " "Am. Yellow warbler " "American bittern " \
"American black duck " "American coot " "American golden plover " "American kestrel " \
"American redstart " "American robin " "Arctic skua " "Arctic tern " \
"Azure-winged magpie " "Baillon's crake " "Barbary partridge " "Barn owl " \
"Barred warbler " "Barrow's goldeneye " "Bewick's swan " "Black and white warbler " \
"Black grouse " "Black guillemot " "Black kite " "Black redstart " \
"Black swan " "Black tern " "Black vulture " "Black wheatear " \
"Black-bellied sandgrouse " "Black-billed cuckoo " "Black-eared wheatear " "Black-faced bunting " \
"Black-necked grebe " "Black-tailed godwit " "Black-throated diver " "Black-throated green warbler " \
"Blackbird " "Blackcap " "Blackpoll warbler " "Blue tit " \
"Blue-cheeked bee-eater " "Blue-headed wagtail " "Blue-winged teal " "Bobolink " \
"Bohemian waxwing " "Bonaparte's gull " "Booted eagle " "Brambling " \
"Brent goose " "Bridled tern " "Broad-billed sandpiper " "Brown thrasher " \
"Brunnich's guillemot " "Bufflehead " "Bullfinch " "Bulwer's petrel " \
"Canada goose " "Cape May warbler " "Capercaillie " "Carrion crow " \
"Chaffinch " "Chiffchaff " "Cirl bunting " "Citrine wagtail " \
"Common bulbul " "Common buzzard " "Common coot " "Common crane " \
"Common gull " "Common kestrel " "Common kingfisher " "Common noddy " \
"Common quail " "Common rosefinch " "Common scoter " "Common starling " \
"Common swift " "Common tern " "Common waxbill " "Corncrake " \
"Cream-coloured courser " "Crested auklet " "Crested lark " "Curlew " \
"Desert lark " "Dipper " "Dotterel " "Dunlin " \
"Dunnock " "Eagle owl " "Eastern turtle dove " "Egyptian vulture " \
"Eider " "European bee-eater " "European nightjar " "Evening grosbeak " \
"Fan-tailed warbler " "Fieldfare " "Forster's tern " "Fox sparrow " \
"Franklin's gull " "Gadwall " "Gannet " "Garden warbler " \
"Giant petrel " "Glaucous gull " "Glossy ibis " "Goldcrest " \
"Golden eagle " "Golden oriole " "Golden plover " "Goldeneye " \
"Goosander " "Goshawk " "Grasshopper warbler " "Great bustard " \
"Great crested grebe " "Great northern diver " "Great reed warbler " "Great skua " \
"Great tit " "Greater black-backed gull " "Greater flamingo " "Green woodpecker " \
"Greenfinch " "Grey catbird " "Grey heron " "Grey partridge " \
"Grey phalarope " "Grey wagtail " "Grey-cheeked thrush " "Grey-headed gull " \
"Grey-headed woodpecker " "Griffon vulture " "Guillemot " "Gyrfalcon " \
"Harlequin " "Hawfinch " "Hawk owl " "Hen harrier " \
"Hermit thrush " "Herring gull " "Hobby " "Hooded warbler " \
"Hoopoe " "House sparrow " "Hudsonian godwit " "Iceland gull " \
"Icterine warbler " "Indigo bunting " "Isabelline wheatear " "Jackdaw " \
"Jay " "Kentish plover " "King eider " "Kittiwake " \
"Lanner " "Lapland bunting " "Lapwing " "Laughing gull " \
"Leach's storm petrel " "Least bittern " "Least sandpiper " "Lesser black-backed gull " \
"Lesser scaup " "Lesser yellowlegs " "Little auk " "Little bittern " \
"Little bunting " "Little grebe " "Little green heron " "Little gull " \
"Little ringed plover " "Long-eared owl " "Long-tailed duck " "Long-tailed skua " \
"Long-tailed tit " "Magnificent frigate bird " "Magpie " "Mallard " \
"Manx shearwater " "Marsh tit " "Marsh warbler " "Meadow pipit " \
"Melodious warbler " "Merlin " "Mistle thrush " "Moorhen " \
"Moussier's redstart " "Mute swan " "Night heron " "Northern mockingbird " \
"Northern oriole " "Northern waterthrush " "Nutcracker " "Orphean warbler " \
"Oystercatcher " "Parula warbler " "Pectoral sandpiper " "Penduline tit " \
"Peregrine " "Pheasant " "Pied flycatcher " "Pied kingfisher " \
"Pied wheatear " "Pied-billed grebe " "Pin-tailed sandgrouse " "Pink-footed goose " \
"Pintail " "Pomarine skua " "Pratincole " "Puffin " \
"Purple heron " "Purple swamphen " "Radde's warbler " "Raven " \
"Razorbill " "Red crossbill " "Red grouse " "Red-backed shrike " \
"Red-breasted merganser " "Red-breasted nuthatch " "Red-eyed vireo " "Red-footed booby " \
"Red-knobbed coot " "Red-necked grebe " "Red-necked nightjar " "Red-necked phalarope " \
"Red-rumped swallow " "Red-throated diver " "Redshank " "Redwing " \
"Reed bunting " "Reed warbler " "Richard's pipit " "Ring ouzel " \
"Ring-billed gull " "Ring-necked duck " "Ringed plover " "Robin " \
"Rock (feral) dove " "Rook " "Rose-breasted grosbeak " "Rose-coloured starling " \
"Roseate tern " "Rough-legged buzzard " "Ruddy duck " "Ruff " \
"Rufous-sided towhee " "Sabine's gull " "Sand martin " "Sandhill crane " \
"Sardinian warbler " "Scarlet tanager " "Scaup " "Scops owl " \
"Sedge warbler " "Semipalmated plover " "Shag " "Shore lark " \
"Short-billed dowitcher " "Short-eared owl " "Shoveler " "Siberian jay " \
"Siberian thrush " "Siberian tit " "Siskin " "Sky lark " \
"Slate-coloured junco " "Slavonian grebe " "Slender-billed gull " "Snipe " \
"Snow bunting " "Song sparrow " "Song thrush " "Sooty tern " \
"Sora " "Sparrowhawk " "Spotted crake " "Spotted flycatcher " \
"Spotted sandpiper " "Stock dove " "Stone curlew " "Storm petrel " \
"Summer tanager " "Swainson's thrush " "Swallow " "Taiga treecreeper " \
"Tawny pipit " "Teal " "Tennessee warbler " "Three-toed woodpecker " \
"Tickell's thrush " "Tree pipit " "Tree sparrow " "Upland sandpiper " \
"Veery " "Velvet scoter " "Wandering albatross " "Wheatear " \
"Whimbrel " "White stork " "White wagtail " "White-billed diver " \
"White-crowned sparrow " "White-faced storm petrel " "White-faced whistling duck " "White-fronted goose " \
"White-rumped swift " "White-tailed eagle " "White-throated sparrow " "Whitethroat " \
"Whooper swan " "Wigeon " "Willet " "Willow warbler " \
"Wood lark " "Wood pigeon " "Wood thrush " "Wood warbler " \
"Woodcock " "Wryneck " "Yellow-billed cuckoo " "Yellow-headed blackbird " \
"Yellow-rumped warbler " "Yellowhammer " "Yellowthroat "
}
#define global variables
global width height
global PARAM pA pE pL vol surf np T ex1 ex2
global COLORS nCOLORS nc
#############################################################################
## Procedures
#############################################################################
proc AssignParam {} {
global PARAM pA pE pL vol nc ex1 ex2 T
set ind [.lb curselection]
set temp [lindex $PARAM $ind]
set pval [split $temp " "]
set pA [lindex $pval 1 ]
set pE [lindex $pval 3 ]
set pL [lindex $pval 5 ]
set nc [expr $nc+1]
set lam [expr $pA+1.0]
set T [expr 1.0/($pE+1.0)]
set ex1 [expr 1.0/(1.0+$lam)]
set ex2 [expr $lam/(1.0+$lam)]
DrawFn .cv
}
proc f {x} {
#
global ex1 ex2 T
set x1 [expr 1.0+$x]
set x2 [expr 1.0-$x]
set y [expr ($T*pow($x1,$ex1)*pow($x2,$ex2))]
return [expr pow($y,2.0)]
}
proc df {x} {
#
global ex1 ex2 T
set x1 [expr 1.000001+$x]
set x2 [expr 1.000001-$x]
set y [expr ($T*pow($x1,$ex1)*pow($x2,$ex2))]
set dy [expr $T*($ex1*pow($x1,$ex1-1.0)*pow($x2,$ex2)-$ex2*pow($x1,$ex1)*pow($x2,$ex2-1.0))]
return [expr $y*sqrt(1.0+pow($dy,2.0))]
}
proc Simpson {f} {
global np
set delta [expr {2.0 / $np}]
set total 0.0
for {set i 0} {$i < $np} {incr i} {
set x1 [expr {-1.0+$i * $delta}]
set x2 [expr {$x1 + $delta}]
set mid [expr {($x1 + $x2) / 2.0}]
set simp [expr {([$f $x1] + 4*[$f $mid] + [$f $x2]) / 6.0}]
set total [expr {$total + $delta * $simp}]
}
return $total
}
proc CalcVol {} {
global pL
set pi 3.14159265359
set coeff [expr $pi*pow($pL,3.0)/8.0]
set res [expr [Simpson f]]
return [expr $coeff*[Simpson f]]
}
proc CalcSur {} {
global pL
set pi 3.14159265359
set coeff [expr $pi*pow($pL,2.0)/2.0]
return [expr $coeff*[Simpson df]]
}
proc GenSTL {} {
global np
global ex1 ex2 T
set nrot 20
set dthe 0.3141
set delta [expr {2.0 / $np}]
for {set i 0} {$i < $np} {incr i} {
set x [expr {-1.0+$i * $delta}]
set x1 [expr 1.0+$x]
set x2 [expr 1.0-$x]
set y [expr ($T*pow($x1,$ex1)*pow($x2,$ex2))]
for {set j 0} {$j < $nrot } {incr j} {
set t [expr {$dthe*$j}]
set x1 [expr $x*10.]
set y1 [expr $y*cos($t)*10.]
set z1 [expr $y*sin($t)*10.]
puts "C $x1 $y1 $z1"
}
}
}
proc ClrCanvas {w } {
global rmin rmax width height ymax ymin midX midY
global nc
$w delete "all"
set nc 0
DrawAxis $w
}
proc DrawAxis {w} {
global rmin rmax width height ymax ymin midX midY
set midX [expr { $width / 2 }]
set midY [expr { $height / 2 }]
set incrX [expr { ($width-50) /10 }]
set incrY [expr { $height /11 }]
$w create line 0 $midY $width $midY -tags "Xaxis" -fill black -width 1
$w create line $midX 0 $midX $height -tags "Yaxis" -fill black -width 1
$w create text [expr $midX-20] 20 -text "Y"
$w create text [ expr $width-20] [expr $midY+20] -text "X"
}
proc DrawFn w {
#
# Plot the 2D egg shape using the Bakker equation
#
global pA pE pL vol surf
global ex1 ex2 lam np T COLORS nCOLORS nc
global rmin rmax width height ymax ymin midX midY
set lam [expr $pA+1.0]
set T [expr 1.0/($pE+1.0)]
set ex1 [expr 1.0/(1.0+$lam)]
set ex2 [expr $lam/(1.0+$lam)]
# ClrCanvas .cv
set divy [expr ($ymax-$ymin)/$height ]
set divx [expr ($rmax-$rmin)/$width]
set divx 200
set asp_ratio 1.6
set ctype [lindex $COLORS [expr $nc%$nCOLORS]]
set yp 0
set yp1 0
set xp 0
DrawAxis $w
for { set n 0 } { $n <= [expr 2*$divx] } { incr n 1 } {
set x0 [expr ($n-$divx)/($divx*1.0)]
set x1 [expr 1.0+$x0]
set x2 [expr 1.0-$x0]
set x [expr $midX+$n-$divx]
set y [expr $midY- ($T*pow($x1,$ex1)*pow($x2,$ex2))/$divy*$asp_ratio]
set y1 [expr $midY+ ($T*pow($x1,$ex1)*pow($x2,$ex2))/$divy*$asp_ratio]
if {$n > 0} {
.cv create line $xp $yp $x $y -fill $ctype -width 2
.cv create line $xp $yp1 $x $y1 -fill $ctype -width 2
}
set yp $y
set yp1 $y1
set xp $x
}
set vol [CalcVol]
set surf [CalcSur]
}
###############################################################################################
#
# Main with the setup up of the GUI
###############################################################################################
# Row 1
label $base.label#0 \
-background magenta -padx 64 -relief raised -text {Egg Calculator (c) Danilo Roccatano 2002-2018}
label $base.label#4 \
-background magenta -padx 64 -relief raised -text {List of European Birds}
# Row 2
label $base.label#1 -background yellow -relief groove -text "Ellipcity:"
entry $base.pE -cursor {} -textvariable pE -bg white
label $base.label#3 -background orange -relief groove -text "Lenght of the egg (cm):"
entry $base.pL -textvariable pL -bg white
# row 3
label $base.label#5 -background brown -relief groove -text "Asymmetry:"
entry $base.pA -cursor {} -textvariable pA -bg white
label $base.label#6 -background green -relief groove -text "Volume (cm^3):"
label $base.label#7 -background green -relief groove -textvariable vol
label $base.label#8 -background green -relief groove -text "Surface (cm^2)"
label $base.label#9 -background green -relief groove -textvariable surf
canvas $base.cv -bg white -height $maxY -width $maxX
# row 6
button $base.plot -text PLOT -command { DrawFn .cv }
button $base.stl -text STL -command { GenSTL }
button $base.b0 -text "Clear" -command { ClrCanvas .cv }
button $base.b1 -text "EXIT" -command { exit -1}
text $base.t -width 50 -height 5 -wrap word -bg gray90
.t insert end "Calculation of the shape of eggs using the Baker equation
y = T*(1+x)^(1/1+lam)(1-x)^(lam/(1+lam)).
The shape of the curve is defined by the asymmetry: A=lam-1, and the
ellipticity: E=1/T-1, input parameters."
scrollbar .s -command ".l yview"
listbox .lb -yscroll ".s set" -exportselection 1
foreach item $CNAMES {
.lb insert end $item
}
#
# Add contents to grid
#
# Row 1
grid $base.label#0 -in $root -row 1 -column 1 -columnspan 5 -sticky nesw
# Row 2
grid $base.label#1 -in $root -row 2 -column 1 -sticky nesw
grid $base.pE -in $root -row 2 -column 2 -sticky nesw
grid $base.label#3 -in $root -row 2 -column 3 -sticky nesw
grid $base.pL -in $root -row 2 -column 4 -sticky nesw
grid $base.label#4 -in $root -row 2 -column 5 -sticky nesw
# Row 3
grid $base.label#5 -in $root -row 3 -column 1 -sticky nesw
grid $base.pA -in $root -row 3 -column 2 -sticky nesw
grid $base.label#6 -in $root -row 3 -column 3 -sticky nesw
grid $base.label#7 -in $root -row 3 -column 4 -sticky nesw
grid $base.lb -in $root -row 3 -rowspan 7 -column 5 -sticky nesw
grid $base.label#8 -in $root -row 4 -column 3 -sticky nesw
grid $base.label#9 -in $root -row 4 -column 4 -sticky nesw
#
# Row 5 (Canvas)
grid $base.cv -in $root -row 5 -column 1 -columnspan 4 -sticky nesw
# Row 6
grid $base.t -in $root -row 6 -column 1 -columnspan 4 -sticky nesw
# Row 7
grid $base.b0 -in $root -row 7 -column 1
grid $base.plot -in $root -row 7 -column 2
grid $base.stl -in $root -row 7 -column 3
grid $base.b1 -in $root -row 7 -column 4
# additional interface code
bind .cv <Double-1> { onDblClick %x %y }
bind $base.pA <Return> {DrawFn .cv}
bind $base.pE <Return> {DrawFn .cv }
bind $base.pL <Return> {DrawFn .cv }
bind .lb <Double-1> {AssignParam}
update
# end additional interface code
set width [winfo width .cv ]
set height [winfo height .cv ]
DrawAxis .cv
daniloroccatano.blog 
Pingback: Modelling Natual Pattern: (Easter) Eggs 2020! | Danilo Roccatano
Pingback: Modelling Forms in Nature: Easter Chocolate Eggs 2021 | Danilo Roccatano