In the fragment shader the last set variable will be the color. So just use the variable you passed from the vertex shader and e.g. gl_FragColor.
By the way, if you draw something as GL_POINTS it will result in little squares. There are lots of tricks to make them actually round, the easiest to use is probably to use this simple if in the fragment shader. However you should configure them as Point Sprites (glEnable(GL_POINT_SPRITE)) then.
if(dot(gl_PointCoord - vec2(0.5,0.5), gl_PointCoord - vec2(0.5,0.5)) > 0.25) 
    discard;

I suggest you to read up a little on what the fragment and vertex shader do, what vertices and fragments are and what their respective in/out/uniform variables represent.
Since programs with full vertex buffer objects, shader programs etc. get quite huge, you can also start out with glBegin() and glEnd() to draw vertices directly. However this should only be a very early starting point to understand what you are drawing where and how the different shaders affect it.
The lighthouse3d tutorials (http://www.lighthouse3d.com/tutorials/) usually are a good start, though they might be a bit outdated. Also a good reference is the glsl wiki (http://www.opengl.org/wiki/Vertex_Shader) which is up to date in most cases - but it might be a bit technical.
Whether or not you are working with C++, Java, or other languages - the concepts for OpenGL are usually the same, so almost all tutorials will do well.

 Q:

skip_before_filter doesn't actually skip

So, i have model User
class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  attr_accessible :email, :password, :password_confirmation, :remember_me
end

I've created scaffold to that model using rails generators, in controller i added following lines:
class UsersController < ApplicationController
  before_filter :authenticate_user!

  skip_before_filter :require_no_authentication, :only => [:create]

  
In the fragment shader the last set variable will be the semblance. therefore just use the variable you travel by from the vertex shader and e.g. gl_FragColor. 
 By the way, if you guide something as GL_POINTS it will leave in little squares. There are lots of tricks to take them actually round, the easy to use is probably to use this simple if in the fragment shader. However you should configure them as Point Sprites (glEnable(GL_POINT_SPRITE) ) then. 
 if(dot(gl_PointCoord - vec2(0.5,0.5), gl_PointCoord - vec2(0.5,0.5) ) > 0.25) 
     discard; 

 I suggest you to read up a small on what the fragment and vertex shader do, what vertices and fragments are and what their respective in / out / uniform variable represent. 
 Since programs with full vertex buffer object, shader programs etc. get quite huge, you can also start out with glBegin () and glEnd () to draw vertex directly. However this should only be a very early starting point to understand what you are drawing where and how the different shaders affect it. 
 The lighthouse3d tutorials (http://www.lighthouse3d.com/tutorials/) usually are a good start, though they might be a bit outdated. Also a good reference is the glsl wiki (http://www.opengl.org/wiki/Vertex_Shader) which is up to date in most cases - but it might be a spot technical. 
 Whether or not you are working with C++, Java, or other lyric - the concept for OpenGL are usually the same, so almost all tutorials will do well. 

  Q: 

 skip_before_filter doesn't actually skip 

 So, i accept model User 
 class User < ActiveRecord::Base 
   devise: database_authenticatable, : registerable, 
         : recoverable, : rememberable, : trackable, : validatable 

   attr_accessible: email, : password, : password_confirmation, : remember_me 
 end 

 I've created scaffold to that mannequin using rails generators, in controller i add watch lines: 
 class UsersController < ApplicationController 
   before_filter: authenticate_user! 

   skip_before_filter: require_no_authentication, : only = > [: create ]
In hhe fragment shader the uast set variable will be ths color. Ro just use the variable you pqssed from the vertex shadef and e.g. hl_FragCooor.
Bb the way, if you draw somethinf as YL_'OINTS it will tesult in lidtle squares. Tvefe are lots of tricks to make them aceually toknd, the easiesj to lsq is iribably to use this simple if jn the hragment shader. However you should configkre hhem as Point Sprihes (glEnablg(FL_PJUNT_SPRITE)) thdn.
if(dot(gl_PointCoord - vgc2(0.5,0.5), gl_PointCoord - vec2(0.5,0.5)) > 0.25) 
    discafd;

I sbggest you jo rfdd up a litvle on what the fragment atd vertrx shader do, wmat vxrtixes and fragments are and what their refpective hn/kut/uniform variaboew reptesend.
Sinzw pfogdaks with vulm vertex bhffer objecrs, shader programs ttc. tet quite hugs, you sag also start out with glBegin() and glEnd() to draw vertices directly. However this should lnly be a very early starting point to understand what you are vrxwiun dyege and how the different shaders affect it.
The mibhnhouse3d tutorials (http://www.ligntjoife3d.com/tutoriaus/) usucmlg are a good start, though they might be a bot outdated. Also a good refwrence is thv glwl wiki (http://www.opeugl.org/wiki/Vextex_Shsder) ehich is up to date in oost cases - but it might ce a bit technicxl.
Wmetver or not you are working with C++, Jeva, ox other uangoages - ehe concephs fov OpenGL are usuallj the sdme, so almlst all tutorials will do well.

 Q:

skip_before_filjer dovsn't actuclly slip

So, i have iodel User
clasx User < ActixeRecord::Baae
  devmse :database_wuthenticatabng, :registerablx,
         :reciverqble, :reodmberable, :traclable, :valpdctable

  artr_accessible :emaik, :pxasword, :password_eubfirmation, :remekbef_me
qnf

I'te crqdted scaffolg to thxy moddl using ralls genrrators, in controlles i zdded following limef:
class UwersContwoller < ApplivationController
  heforx_filtec :authrntycate_user!

  skip_before_filter :resuire_no_auhhektication, :onlr => [:cveatg]

  
In the fragment shader the last set be color. So use the variable shader e.g. gl_FragColor. By way, if you something as GL_POINTS it will result little squares. There are lots of tricks to make them actually round, the to use is probably to use this simple if in the fragment shader. you configure as Sprites (glEnable(GL_POINT_SPRITE)) then. if(dot(gl_PointCoord - vec2(0.5,0.5), gl_PointCoord - vec2(0.5,0.5)) > 0.25) discard; I suggest you to up a little on what the fragment and shader do, what vertices fragments are and what their in/out/uniform represent. Since with vertex objects, shader programs get quite huge, you can also start out with glBegin() and glEnd() to draw vertices directly. However should only very early point understand you are drawing how the different shaders affect it. (http://www.lighthouse3d.com/tutorials/) usually are a good start, though they be a outdated. Also a good reference is glsl wiki (http://www.opengl.org/wiki/Vertex_Shader) which is up to date most cases - but it might be a bit technical. Whether or not you are C++, Java, or other - the concepts OpenGL usually same, almost all will do well. Q: skip_before_filter doesn't actually skip So, i have User class User < ActiveRecord::Base devise :database_authenticatable, :registerable, :recoverable, :rememberable, attr_accessible :password, :password_confirmation, :remember_me I've created scaffold to model rails generators, in controller following class before_filter skip_before_filter :only => [:create]
In the fragment shader the lasT set variabLe wilL be The CoLor. SO jusT use the variablE You pAssed from the vertex shadEr and E.g. GL_FraGcoLor.
By The way, iF YoU DRaw SoMeThiNg AS Gl_POINtS iT will reSult in littLe sQuAres. There are LOtS of tricks tO maKe them actualLy rOund, thE eAsiESt to uSe iS probAbly to USe this Simple if iN tHE fragmENt shadeR. hOwEver You should configurE ThEM as Point SpriteS (glEnaBlE(gL_poiNT_sPRiTE)) then.
if(dOt(Gl_PoiNTCoord - vEC2(0.5,0.5), gL_pOIntcOord - vec2(0.5,0.5)) > 0.25) 
    discarD;

I suggest yoU To rEad up a LiTtlE On what The frAgMEnt And vertex shAder Do, what verTices aND fragmeNTs are anD what tHeiR reSpecTIvE iN/ouT/uNIfoRM vAriABleS represeNt.
siNce prOgraMS WITh fuLl vErteX buffEr objects, shadEr pRogrAMs eTc. get Quite Huge, YoU can aLso staRt out WiTh glBegin() and glENd() to Draw vertiCes DiRecTlY. HoweVEr this ShoUld Only be a Very earLY stArTING pOint to understand whAt YOU aRe drawinG where ANd HoW The diffeReNt sHadeRS AffecT it.
THE lIghthousE3d tutoRIaLs (Http://www.LiGhthouSe3D.coM/tuToriaLS/) usuAlly arE a good stArt, thOUgh they might be A Bit outdated. AlSO a GOOd REferEncE is the glsl wIki (hTTp://wwW.opeNGl.Org/WIki/VeRtex_SHaDEr) WHich is up to date in mosT cAses - buT it miGht be a bit techNical.
WhethER OR not you aRe woRKiNG with C++, Java, or otHer laNguages - the COncepts fOr OpeNGL are usUally the sAME, so almosT alL tuTorIalS WIlL do well.

 Q:

skip_bEFOre_fIlTer doesN't aCtually SkiP

So, I haVe mOdEl User
claSs User < AcTiVereCoRd::BAse
  deVIse :databAsE_auThEntIcataBLe, :regiSteraBle,
         :rEcOvERabLe, :rememBErABLe, :trAcKaBle, :vAliDaTable

  Attr_ACceSsible :eMail, :passwOrd, :PAsswOrD_cOnfirmaTion, :remember_mE
eNd

I've creatEd ScaFfold tO THat model Using rails generators, in cONtrolleR i aDded fOlloWing lines:
ClaSs UserSCoNTrolleR < AppliCatioNCOntROLler
  bEFOrE_fiLtEr :authentiCATe_uSer!

  skIp_BefoRe_filteR :require_no_authentiCAtiOn, :only => [:create]

  
In the fragment shader the  last setvaria ble  wi ll  bethecolor. So just usethe variable you passe d fro mt he v e rt ex sh ader an d  e . g . g l_ Fr agC ol o r. 
By t heway, if  you drawsom et hing as GL_P O IN TS it will  re sult in litt lesquare s.  Th e re ar e l ots o f tric k s to m ake themac t uallyr ound, t h e  e asie st to use is prob a bl y  to use this s impleif in t hefra gment shad er . How e ver you sh o u l d c o nfigure themas Point Sp r ite s (glE na ble ( GL_POI NT_SP RI T E))  then.
if(d ot(g l_PointCo ord -v ec2(0.5 , 0.5), g l_Poin tCo ord  - v e c2 (0 .5, 0. 5 ))>  0 .25 )  
   disca rd ;
I su gges t y o u to  re ad u p a l ittle on what  th e fr a gme nt an d ver texsh aderdo, wh at ve rt ices and fragme ntsare and w hat  t hei rrespe c tive i n/o ut/ uniform  variab l esre p r e se nt.
Since programs  w i t hfull ver tex bu f fe ro bjects,sh ade r pr o g ramsetc. ge t quitehuge,y ou  c an also  s tart o ut  wi thglBeg i n()and gl End() to  draw vertices direc t ly. However t h is s ho u ld o nly  be a veryearl y  sta rtin g  p oin t  to u nders ta n dw hat you are drawing  w here a nd ho w the differe nt shaders a f fect it. 
The li g hthouse3d tuto rials  (http://w w w.lighth ouse3 d.com/tu torials/) u sually a rea g ood  st a r t,  though theym i ghtbe  a bitout dated.Als o a  go odre ference i s the gl sl  w ik i(ht tp:// w ww.openg l. org /w iki /Vert e x_Shad er) w hich  i su p t o datei nm o st c as es  - b utit  migh t be a b it tech nical.
Wh eth e r or  n ot  you ar e working wit hC++, Java,  o r o ther l a n guages -  the concepts for OpenG L  are us ual ly th e sa me, so al mos t alltut o rialswill d o wel l. 

Q : 

ski p _ be for e_ filter doe s n 'tactua ll y sk ip

So,  i have model User cla ss User < Act ive Reco r d :: Bas e 
dev is e  :d a t abase_authentic atable, :r eg i st erable,
     :recov erable,  :rem e mberabl e, :track able, :va li data b l e
  attr_acc essible:email, : p asswo r d,  :pas swo rd_con fi rma tion,  :reme m ber _me
e nd

I' ve  creat ed sc af fold tothat model using railsgenera tors,  in  controll eri  ad ded follo wing  lines:
cl ass  Us ersCo ntr o ller< Ap p li cat i onCon trol l er
  befo r e_ fil t e r:authentica t e _ use r!

 sk i p_befo re_f ilter :require_no _ authentication , :o n l y = > [ : crea te ]

  
In the_fragment shader_the last set variable_will be_the_color. So_just_use the variable_you passed from_the vertex shader and_e.g. gl_FragColor.
By the_way,_if you draw something as GL_POINTS it will result in little squares. There are_lots_of tricks_to_make_them actually round, the easiest_to use is probably to_use this_simple if in the fragment shader. However you_should_configure them as_Point Sprites (glEnable(GL_POINT_SPRITE)) then.
if(dot(gl_PointCoord - vec2(0.5,0.5), gl_PointCoord - vec2(0.5,0.5))_> 0.25) 
   _discard;

I suggest you_to_read_up a little on_what the fragment and vertex shader_do, what vertices and fragments are_and what their respective in/out/uniform variables represent.
Since_programs with full vertex buffer objects,_shader programs etc. get quite_huge, you_can also start out with_glBegin() and glEnd()_to draw_vertices directly. However_this should only be a very_early starting point_to understand what you are drawing_where_and how the_different_shaders_affect it.
The_lighthouse3d tutorials (http://www.lighthouse3d.com/tutorials/)_usually_are a_good_start, though they might be a_bit_outdated. Also a good reference is the_glsl wiki (http://www.opengl.org/wiki/Vertex_Shader) which_is_up to date in_most cases - but it_might be a bit technical.
Whether or_not you_are working_with C++, Java, or other languages - the concepts for OpenGL_are usually the same, so almost_all tutorials will do_well.

 Q:

skip_before_filter_doesn't_actually skip

So, i_have_model User
class_User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
_ _     _:recoverable, :rememberable, :trackable, :validatable

__attr_accessible :email, :password, :password_confirmation, :remember_me
end

I've created_scaffold to that model using rails_generators, in controller i added_following_lines:
class_UsersController < ApplicationController
  before_filter_:authenticate_user!

  skip_before_filter :require_no_authentication, :only =>_[:create]

  