RayTracer Theory and Practice

Dreglor · Post by **Dreglor** » Mon Jun 13, 2005 12:43 am

Im, doing a bit of research into ray tracing in writing one eventually
i can at least try and write a pretty low quality raytracer using longs and floats

then later convert to double when 4.0 comes out.

so im kinda new on RayTracing and im just starting to grasp the idea so could you point me into any good papers code that would be helpsful
even writing a bit of code to help start it off

DarkDragon · Post by **DarkDragon** » Mon Jun 13, 2005 6:23 am

In the german forum NicTheQuick has made the best Raytracing results. Then there's Deeem2031 and me.

Here is the Topic:
http://forums.purebasic.com/german/viewtopic.php?t=3505

It's about realtime Raytracing with Adaptive Subsampling. NicTheQuick works on it right now, I have no time and I don't know how it is about deeem.

Uhm and here a useful link:
http://www.demoscene.hu/~picard/h7/subs ... ample.html

[EDIT]
VERY SHORT Explanation:
We send our rays from the screen out to the world and check if it collides with objects. If yes we draw the pixel on our screen. If not: we don't do so.

In my example you can see the tracemap and manipulate the adaptive subsampling through key 1, 2, 3, (maybe implemented) 4

Dreglor · Post by **Dreglor** » Mon Jun 13, 2005 6:33 am

I been Looking around and i found some sources for ray tracers (in c++) but i find it difficult to convert it

i know of a raytracer called realstorm http://www.realstorm.com/
cheack it out it very fast compared to that ray tracer.

the problem i have under standing the core of ray tracing mathimaticly

Num3 · Post by **Num3** » Mon Jun 13, 2005 10:16 am

Try the wolfenstein source code

It's free now!

http://www.gamespp.com/sourcecode/wolfenstein.html

thefool · Post by **thefool** » Mon Jun 13, 2005 10:52 am

eh is that raytracing??

edit:
@num3: you are talking about raycasting, wich is NOT the same

try a search on google.

dagcrack · Post by **dagcrack** » Mon Jun 13, 2005 11:29 am

Num3 · Post by **Num3** » Mon Jun 13, 2005 11:55 am

thefool wrote:eh is that raytracing??

edit:
@num3: you are talking about raycasting, wich is NOT the same
try a search on google.

DOH !

dagcrack · Post by **dagcrack** » Mon Jun 13, 2005 12:07 pm

noo that reminds me I forgot to watch the simpsons today!!

Trond · Post by **Trond** » Mon Jun 13, 2005 8:27 pm

VERY SHORT Explanation:
We send our rays from the screen out to the world and check if it collides with objects. If yes we draw the pixel on our screen. If not: we don't do so.

Why isn't raytracing and raycasting the same?

Raytracing: You send rays from the screen and trace them "backwards" towards objects and light sources.

Raycasting: You cast rays from the screen and trace them backwards towards objects and light sources.

????????? What I am doing wrong??

yashaa · Post by **yashaa** » Mon Jun 13, 2005 9:04 pm

Raycasting is more "simpler" while raytracing considers a lot of variables (i.e. type of material, lights attributes), and the ray bouces in many ways too...

Instead, raycasting draws many rays just to see if a certain object (i.e. wall) can be seen (drawn) from the player point of view...

I M H O

GedB · Post by **GedB** » Mon Jun 13, 2005 9:16 pm

http://www.answers.com/main/ntquery?s=r ... d=2&gwp=13

Dreglor · Post by **Dreglor** » Tue Jun 14, 2005 1:26 am

So is there any pb sources with ray tracing in them and not the ray casting

Blade · Post by **Blade** » Tue Jun 14, 2005 8:55 am

Never seen a PB example, but just googled "simple raytracing" and found this:

http://wiki.tcl.tk/10857

seems pretty easy to convert too. (see the "mathematical details" for a scaring explaination

)

Otherwise search for the freeware (and poweful) POV raytracer sources. Expect a huge and complex C code...

http://www.povray.org

Dreglor · Post by **Dreglor** » Tue Jun 14, 2005 2:47 pm

hmm well at least its a small example
that i can at least understand

and the mathicmatical details provide a better explaination than most sites

Dreglor · Post by **Dreglor** » Mon Jun 20, 2005 7:12 am

Hmm, i tried 2 examples from http://wiki.tcl.tk/10857 and http://www.devmaster.net/articles/raytracing/
Both were failing to work
here is some code that i have that i did from the devmaster tutorial

Code: Select all

#ScreenWidth=320
#ScreenHieght=240

#Tolarance=0.0001

Structure xyz
  x.f
  y.f
  z.f
EndStructure

Structure Sphere
  center.xyz
  radius.f
EndStructure

Procedure VectorNormalize(*this.xyz)
  m.f = Sqr(*this\x * *this\x + *this\y * *this\y + *this\z * *this\z)
  If m < =#Tolarance
    m = 1
  EndIf
  *this\x = *this\x / m
  *this\y = *this\y / m
  *this\z = *this\z / m
  If  *this\x < #Tolarance
    *this\x = 0
  EndIf
  If  *this\y < #Tolarance
    *this\y = 0
  EndIf
  If  *this\z < #Tolarance
    *this\z = 0
  EndIf
EndProcedure

Procedure.f TestSphere(*Direction.xyz,*Origin.xyz,*Sphere.Sphere)
  dirx=*Direction\x
  diry=*Direction\y
  dirz=*Direction\z
  Originx=*Origin\x
  Originy=*Origin\y
  Originz=*Origin\z
  Spherex=*Sphere\center\x
  Spherey=*Sphere\center\y
  Spherez=*Sphere\center\z
  ;a.f=Pow(*Direction\x,2)+Pow(*Direction\y,2)+Pow(*Direction\z,2)
  ;b.f=2*(*Direction\x*(*Origin\x-*Sphere\center\x)+*Direction\y*(*Origin\y-*Sphere\center\y)+*Direction\z*(*Origin\z-*Sphere\center\z))
  ;c.f=Pow(*Origin\x-*Sphere\center\x,2)+Pow(*Origin\y-*Sphere\center\y,2)+Pow(*Origin\z-*Sphere\center\z,2)
  a.f=Pow(dirx,2)+Pow(diry,2)+Pow(dirz,2)
  b.f=2*(dirx*(Originx-Spherex)+diry*(Originy-Spherey)+dirz*(Originz-Spherez))
  c.f=Pow(Originx-Spherex,2)+Pow(Originy-Spherey,2)+Pow(Originz-Spherez,2)
  D.f=Pow(b,2)-4*a*c
  If D>0 ;hit the sphere
    t.f=(-b-Sqr(D))/(2*a)
  ElseIf D=0 ;glazing the sphere
    t.f=-1
  ElseIf D<0 ;missed completely
    t.f=-2
  EndIf
  ProcedureReturn t
EndProcedure

Origin.xyz
Direction.xyz
Test.Sphere
  
Origin\x=0
Origin\y=0
Origin\z=-256

InitSprite()
OpenWindow(0,0,0,#ScreenWidth,#ScreenHieght,#PB_Window_ScreenCentered|#PB_Window_SystemMenu,"Ray Test")
StartDrawing(WindowOutput())
Repeat
  For y=-#ScreenHieght/2 To (#ScreenHieght/2)-1 Step 1
    For x=-#ScreenWidth/2 To (#ScreenWidth/2)-1 Step 1
      Direction\x=x
      Direction\y=y
      Direction\z=256
      VectorNormalize(Direction)
      t.f=TestSphere(Direction,Origin,Test)
      If t>0
        posx=x+(#ScreenWidth/2)
        posy=y+(#ScreenHieght/2) 
        Plot(posx,posy,RGB(255,0,0))
      ElseIf t=-1
        posx=x+(#ScreenWidth/2)
        posy=y+(#ScreenHieght/2)
        Plot(posx,posy,RGB(0,255,0))
      ElseIf t=-2
        posx=x+(#ScreenWidth/2)
        posy=y+(#ScreenHieght/2)
        Plot(posx,posy,RGB(0,0,255))
      Else
        posx=x+(#ScreenWidth/2)
        posy=y+(#ScreenHieght/2)
        Plot(posx,posy,RGB(255,255,255))
      EndIf
    Next x
  Next y
Until WindowEvent()=#PB_Event_CloseWindow

oddly window rendering gives a bit of the clear screen color o_O
anyways, most of the main code is from the document the vector procedure is from another program i did while back
the problem i see with the code is that radius it not account for in the equasion im wondering where does it go? the tutorial only has a small part at the end of the sphere intersection about it but thats for the normal but that is only for lighting calulcations.

the other tutoral with the code when i converted it returned "behind origin" which i thought i converted wrong, because the code is very odd

im wondering whats missing...

edit : changed the code to fix a few dumb problems but it still returns -2 (glazing the sphere) until the right side of the screen where it returns "missed completely"