Light without Lights :-)

[DJLinux]

save it in your "Basic4GL\Programs" folder or you wan't see the texture from
"Basic4GL\Programs\Textures\floor01.jpg"

Unbelievable but true the dynamic light map is only 8x8 pixels.

Joshy

const SIZE  as integer = 8
const STEPS as single  = 1.0 / SIZE

type SURFACE
  v(3,2) as single
  m0(2)  as single
  m1(2)  as single
  'm2(2)  as single

  sd     as single
  td     as single
end type  


dim lighting    as integer = 1

dim Surfaces(5) as SURFACE
dim SurfaceTexture as integer
dim light_pos(2)   as single
dim buffer(SIZE*SIZE-1) as integer
dim LightTexture as integer


function CreateSurface(v0() as single,v1() as single,v2() as single,v3() as single) as SURFACE
  dim s as SURFACE
  s.v(0) = v0:s.v(1) = v1:s.v(2) = v2:s.v(3) = v3
   ' x axis in texture space
  s.m0 = s.v(3)-s.v(0):s.sd=sqrt(s.m0*s.m0):s.m0=normalize(s.m0)
  ' y axis  in texture space
  s.m1 = s.v(1)-s.v(0):s.td=sqrt(s.m1*s.m1):s.m1=normalize(s.m1)
  return s
end function


sub CreateScene()   
  glClearColor(0.0, 0.0, 0.0, 0.0)
  glClearDepth(1.0)

  glDisable(GL_BLEND)
  glEnable(GL_DEPTH_TEST)
  glColor4f(1.0, 1.0, 1.0, 1.0)

  glMatrixMode(GL_PROJECTION)
  glLoadIdentity()      
  dim ratio as single = WindowWidth()
  ratio = ratio / WindowHeight()
  gluPerspective(45.0, ratio, 0.1, 200.0)
  
  glMatrixMode(GL_MODELVIEW)
                               
  
  glActiveTexture(GL_TEXTURE1)
  glEnable(GL_TEXTURE_2D)
  LightTexture = glGenTexture()
  glBindTexture(GL_TEXTURE_2D, LightTexture)
  glPixelStorei(GL_UNPACK_ALIGNMENT, 1)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE)

  glActiveTexture(GL_TEXTURE0)
  glEnable(GL_TEXTURE_2D)
  SurfaceTexture = LoadMipMapTexture("Textures\floor01.jpg")
  glBindTexture(GL_TEXTURE_2D, SurfaceTexture)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE)

  Surfaces(0)=CreateSurface(vec3(-1.0,-1.0, 3.0),vec3(-1.0,-1.0, 1.0),vec3( 1.0,-1.0, 1.0),vec3( 1.0,-1.0, 3.0))
  Surfaces(1)=CreateSurface(vec3( 1.0, 1.0,-1.0),vec3( 1.0,-1.0,-1.0),vec3(-1.0,-1.0,-1.0),vec3(-1.0, 1.0,-1.0))
  Surfaces(2)=CreateSurface(vec3(-1.0, 1.0, 1.0),vec3(-1.0, 1.0,-1.0),vec3( 1.0, 1.0,-1.0),vec3( 1.0, 1.0, 1.0))
  Surfaces(3)=CreateSurface(vec3( 1.0,-1.0, 1.0),vec3( 1.0,-1.0,-1.0),vec3(-1.0,-1.0,-1.0),vec3(-1.0,-1.0, 1.0))
  Surfaces(4)=CreateSurface(vec3(-1.0, 1.0, 1.0),vec3(-1.0, 1.0,-1.0),vec3(-1.0,-1.0,-1.0),vec3(-1.0,-1.0, 1.0))
  Surfaces(5)=CreateSurface(vec3( 1.0,-1.0, 1.0),vec3( 1.0,-1.0,-1.0),vec3( 1.0, 1.0,-1.0),vec3( 1.0, 1.0, 1.0))
end sub

sub DynamicLightMap(&s as SURFACE)
  dim d    as single
  dim t    as single 
  dim ts   as single
  dim tt   as single 
  dim i    as integer
  dim j    as integer 
  dim k    as integer 
  dim p(2) as single
  dim tdtm1(2) as single
  dim tdt  as single
  dim sdt  as single

  
  for i = 0 to SIZE-1
    ts    = 0.0
    tdt   = s.td * tt
    tdtm1 = tdt * s.m1
    tdtm1 = tdtm1+s.v(0)-light_pos
    for j = 0 to SIZE-1
      sdt = s.sd * ts
      p   = s.m0 * sdt + tdtm1
      d   = p * p
      ' fill the light map
      if (d < 1.0) then 
        buffer(k+j)=196
      else
        buffer(k+j)=196/d
      end if
      ts = ts + steps
    next
    k=k+SIZE
    tt = tt + steps
  next
  glTexImage2D(GL_TEXTURE_2D,0,1,SIZE,SIZE,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,buffer)
end sub


sub RenderScene()
  dim i as integer
  glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT)
  glLoadIdentity()
  glTranslatef(0, 0.0, -5.0)
   
  glActiveTexture(GL_TEXTURE0)
  glEnable(GL_TEXTURE_2D)
  glBindTexture(GL_TEXTURE_2D, SurfaceTexture)

  glActiveTexture(GL_TEXTURE1)
  if(lighting) then glEnable(GL_TEXTURE_2D):end if

  for i = 0 to 5 
    if(lighting) then
      DynamicLightMap(Surfaces(i))
    end if
    glBegin(GL_QUADS)
      glMultiTexCoord2f(GL_TEXTURE0, 0,0)
      glMultiTexCoord2f(GL_TEXTURE1, 0,0)
      glVertex3fv(Surfaces(i).v(0))
      glMultiTexCoord2f(GL_TEXTURE0, 0,1)
      glMultiTexCoord2f(GL_TEXTURE1, 0,1)
      glVertex3fv(Surfaces(i).v(1))
      glMultiTexCoord2f(GL_TEXTURE0, 1,1)
      glMultiTexCoord2f(GL_TEXTURE1, 1,1)
      glVertex3fv(Surfaces(i).v(2))
      glMultiTexCoord2f(GL_TEXTURE0, 1,0)
      glMultiTexCoord2f(GL_TEXTURE1, 1,0)
      glVertex3fv(Surfaces(i).v(3))
    glEnd()
  next  

  glDisable(GL_TEXTURE_2D)
  glActiveTexture(GL_TEXTURE0):glDisable(GL_TEXTURE_2D)
  glColor3f(1,1,0)
  
  glBegin(GL_QUADS)
    glVertex3f(light_pos(0) - 0.02, light_pos(1) + 0.02, light_pos(2))
    glVertex3f(light_pos(0) - 0.02, light_pos(1) - 0.02, light_pos(2))
    glVertex3f(light_pos(0) + 0.02, light_pos(1) - 0.02, light_pos(2))
    glVertex3f(light_pos(0) + 0.02, light_pos(1) + 0.02, light_pos(2))
  glEnd()
  glColor4f(1.0, 1.0, 1.0, 1.0)

  
end sub


CreateScene()

dim light_rot as single


while True
  if inkey$()="l" then 
    lighting=1-lighting
  end if

  light_pos(0) = cos(light_rot) * 0.9
  light_pos(1) = sin(light_rot*2) * 0.8 
  light_pos(2) = 1 + sin(light_rot)*2 
  light_rot = light_rot + 0.01

  RenderScene()
  SwapBuffers()
  Sleep(20)
Wend

[lal7777]

Very Nice!
This reminds me of the lighting in quite a few professional games! (Oblivion for one)
So what is it doing?
Altering the pixels for each image?
I always wondered how games made in opengl were somehow able to fit more than 8 dynamic lights per scene.
(i get about 40 fps with it)

[DJLinux]

Jun 8, 2011 23:10:32 GMT -5 lal7777 said:

(i get about 40 fps with it)

do you comented out the sleep() command ?

Joshy

[lal7777]

I must've forgot to, because when I tried it again I get 155 fps.

[shadow008]

Jun 8, 2011 23:10:32 GMT -5 lal7777 said:

So what is it doing?
Altering the pixels for each image?

Sorta, its actually making a seperate texture and applying the lighting to the texture, and then doing multi-texturing to render to each surface.

Jun 8, 2011 23:10:32 GMT -5 lal7777 said:

I always wondered how games made in opengl were somehow able to fit more than 8 dynamic lights per scene.

Theres actually many ways this can be done. This technique isn't very efficient because the speed of this drops exponentially as the light map size gets bigger. A simple light map for a full scale scene at a resolution of 600x800 would have to loop through each textel and do lighting calculations for them... all 480,000 of them!

Actually, most modern games make custom shaders for their games. The program could pass as many custom lights as it wants to the shader and then the shader handles the lighting computations.

Another way to do it (using the fixed function pipeline for those who dont have GLSL support) would be to render the scene with the first 8 lights, switch to the next 8 lights, then render the scene again. Do that until you've gone through all lights, then blend the scenes together. Not very robust, but it's still an option.