raytracer: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/raytracer - from package: opticalraytracer

You may install the required package with command yum install {package}

Error in other languages:
raytracer: bevel nie gevind nie
raytracer: comandă negăsită
raytracer: comando não encontrado
raytracer: commande introuvable
raytracer: command not found
raytracer: käsku ei ole
raytracer: không tìm thấy lệnh
raytracer: komanda nerasta
raytracer: Kommando nicht gefunden.
raytracer: kommandot finns inte
raytracer: komut yok
raytracer: nie znaleziono polecenia
raytracer: níor aimsíodh an t-ordú
raytracer: no se encontró la orden
raytracer: no s'ha trobat l'ordre
raytracer: opdracht niet gevonden
raytracer: parancs nem található
raytracer: perintah tidak ditemukan
raytracer: príkaz nenájdený
raytracer: příkaz nenalezen
raytracer: команда не найдена
raytracer: командата не е открита
raytracer: 命令找不到
raytracer: コマンドが見つかりません