The Problem

I want to be able to change the colour of parts of lines in Graphics 3D. I don’t know a good way.

Below is how I’ve got so far and a diagram of I want. I.e. I want to be able to control the colour of the line segments from data. The integer value between 400-700nm should be the colour. (these can be simplified if required)

Example Data & Plotting Code

photonlives = {{{"Start", {8.908399661129824`, 9.633102260661355`, 5}, 407}, {"Emission", {8.908399661129824`, 9.633102260661355`, 2.496926971098662`},407}, {"Left", {11.087670534918876`, 8.219492769746015`, 3.432302819553219`},300}}, {{"Start", {1.9856853654615514`, 6.848440992081457`, 5},594}, {"Emission", {1.9856853654615514`, 6.848440992081457`, 2.6228644835985957`},594}, {"Left", {2.521141087121206`, 5.323725115908513`, 3.012965011108447`},300}}, {{"Start", {5.382360511331741`, 4.408513016017577`, 5},524}, {"Emission", {5.382360511331741`, 4.408513016017577`, 2.0636538349485796`},524}, {"Emission", {5.9510903463320135`, 6.191633074632532`, 1.365916379273969`},300}, {"Emission", {4.141206920229977`, 5.773532803626935`, 1.1486020989253132`},300}, {"Absorbed", {4.731487780277531`, 3.5166296163565747`, 0.9018958429272086`},300}}, {{"Start", {5.7064477543041985`, 8.960806835584687`, 5},499}, {"Absorbed", {5.7064477543041985`, 8.960806835584687`, 2.6904886316076606`},499}}, {{"Start", {8.290340872256385`, 2.9730634116539956`, 5},409}, {"Reflection", {8.290340872256385`, 2.9730634116539956`, 3}, 409}, {"Left", {9.25283380442492`, 0.9128219903837054`, 5},409}}, {{"Start", {7.109178085659753`, 1.4811083443707118`, 5},537}, {"Emission", {7.109178085659753`, 1.4811083443707118`, 2.3677442987465627`},537}, {"Left", {5.423234919050124`, -0.4911618443561132`, 1.6554688841042937`},300}}, {{"Start", {3.6761465640204927`, 9.226495379895743`, 5},606}, {"Reflection", {3.6761465640204927`, 9.226495379895743`, 3}, 606}, {"Left", {0.5167471944485746`, 4.671778417759236`, 5}, 606}}, {{"Start", {4.383581619316823`, 2.2526259659816184`, 5},401}, {"Reflection", {4.383581619316823`, 2.2526259659816184`, 3}, 401}, {"Left", {9.404425720369971`, 4.8467050372875775`, 5},  401}}, {{"Start", {1.9099177632828113`, 8.593414202432443`, 5},560}, {"Emission", {1.9099177632828113`, 8.593414202432443`, 2.6092504664365213`},560}, {"Emission", {2.7699445700893683`, 7.423796219035573`, 2.624089283248043`},300}, {"Left", {0.5502206495992263`, 5.467835704409955`, 3.3137618986450716`},300}}, {{"Start", {3.6746266719085408`, 0.28929707744424604`, 5}, 592}, {"Emission", {3.6746266719085408`, 0.28929707744424604`, 2.4109510252927`},592}, {"Emission", {1.8174965321127263`, 2.541633357705031`, 2.7993512767850586`},300}, {"Absorbed", {2.371991341538078`, 0.5034533844835565`, 2.686939720078675`}, 300}}};  Graphics3D[{Line[photonlives[[All, All, 2]]], {Opacity[0.2], Cuboid[{0, 0, 0}, {10, 10, 3}]}}] 

I’m really at a lost end – any idea would be helpful.

Background

I have a program which tracks what photons are doing in a box filled with plastic. It contains a dye which will absorb and re-emit the light at a new colour/frequency. The “frequency in nm” should correspond to a colour

It produces output which gives a list for each photon which describes the life of the photon. It looks like.

{{"Process 1"}, {"x","y","z"}, {"frequency in nm"}, {"Process 2"}, {"x","y","z"}, {"frequency in nm"}, ... }  

An example is

{{"Start", {8.9, 9.6, 5}, 407}, {"Emission", {8.9, 9.6, 2.5}, 407}, {"Left", {11.0, 8.2, 3.4}, 300}} 

Each photon starts which a location with Start. Then, there are 4 processes available – reflection (which means the photon doesn’t get into the box), absorption (which kills the photon in the box), emission (which means the frequency of the photon is changed) and left (which means the photon has left the interesting area).

I have attached the whole code which generates the above figure, in case there might be a better way of dealing with the data.

(* This number of times we track the photon *)  numberofphotons = 1000;  (*array to track the photons *)  photonlives = ConstantArray[0, numberofphotons];  (* the size of our box *)  xbox = 10;  ybox = 10;  zbox = 3;   dyefreq = 300;  For[i = 1, i <= numberofphotons, i++,    Photonabsorbedflag = 0;   (* Photons begin above the box in a random location*)   x = RandomReal[]*xbox;   y = RandomReal[]*ybox;  z = 5;    (* Pick the colour of the photons *)   lamda = RandomInteger[{400, 700}];   (* Record where the photon begins *)   photonlives[[i]] = {{"Start", {x, y, z}, lamda}};    (* Reflection *)   If[ RandomReal[] < 0.4,      (* Find location of reflection *)    photonlives[[i]] =     Append[photonlives[[i]] , {"Reflection", {x, y, 3}, lamda}];    (* Assume the photons are scattered randomly *)    photonlives[[i]] =     Append[photonlives[[i]] , {"Left", {RandomReal[]*xbox,        RandomReal[]*ybox, 5}, lamda}];    (* Begin next photon *)    Continue[]   ];    (* ------- In the Plastic Block -------*)     pathlengthz = RandomReal[]* zbox/3;    z = 3 - pathlengthz;   While[ x > 0 && x < xbox && y > 0 && y < ybox && z > 0 && z < zbox,     (* Photon absorbed by substrate and just dies *)     If[RandomReal[] < 0.2,     photonlives[[i]] =      Append[photonlives[[i]] , {"Absorbed", {x, y, z}, lamda}];    Photonabsorbedflag = 1;     (*breaks while loop*)     Break[];     ];    (* Photon absorbed by dye and remitted at new freq *)    If[RandomReal[] < 0.4,     photonlives[[i]] =      Append[photonlives[[i]] , {"Emission", {x, y, z}, lamda}];     pathlengthx = RandomReal[{-1, 1}]* xbox/3;    pathlengthy = RandomReal[{-1, 1}]* ybox/3;    pathlengthz = RandomReal[{-1, 1}]* zbox/3;     x = x + pathlengthx;    y = y + pathlengthy;    z = z + pathlengthz;     lamda = dyefreq;     (*breaks while loop*)     ];    ];   If[Photonabsorbedflag == 0,    photonlives[[i]] =     Append[photonlives[[i]] , {"Left", {x, y, z}, lamda}]    ];  ] Graphics3D[{Line[photonlives[[All, All, 2]]], {Opacity[0.2],     Cuboid[{0, 0, 0}, {xbox, ybox, zbox}]}}]