Virtual GL

This code has been declared by its author to be Public Domain code.

Virtual GL by N

2004

This is a quick bit of code I wrote in about an hour and a half to simulate OpenGL at a very, very basic level. It's just made out of boredom. Chances are there's no good reason to use it, but I'll keep adding to it until I'm satisfied ^_^

Update: Fixed some stuff with the texturing. Added an untested triangle fan handler, I'm pretty sure it should work, but I won't know 'til someone tries it. Added vglEnable/Disable, only two of the enumerators are true to OpenGL though.

Update 2: Fixed the triangle fan code. Added fake Push/PopMatrix functions. Changed vglLoadTexture() so it returns the handle of the Surface object instead of a reference to it.

;VGL Example

Graphics3d 800,600,32,2

;Include "vgl.bb"

vglInit()

;EntityFX vglDisplayMesh,1+2+16

;PART_FIRE = vglLoadTexture("part_fire.tga",1)     ;;;  UNCOMMENT THIS IS YOU'VE GOT A TEXTURE TO USE.

;vglEnable(VGL_CULL_FACE)
vglEnable(VGL_AUTO_NORMAL)
vglDisable(VGL_VERTEX_ALPHA)

UsePushPop = True

Repeat
     vglClear(VGL_COLOR_BUFFER_BIT)

     vglBegin(VGL_TRIANGLE_FAN)
          vglVertex3f(0,0,0)
          vglColor4f(0,1,0,1)
          For X = 0 To 32
               vglVertex3f(Sin(X*11.25),Cos(X*11.25),0)
               vglColor4b(Sin(X*11.25)*255,Cos(X*11.25),X*7.96875,128)
          Next
     vglEnd()

     vglRotatef(Float(Millisecs())/60,.5,1,.25)
     vglTranslatef(0,0,4)

     If Keyhit(57) Then UsePushPop = Not UsePushPop
     If UsePushPop Then vglPushMatrix()
          vglBegin(VGL_TRIANGLES)
               vglVertex3f(-1,-1,0)
               vglColor4f(1,0,0,1)
               vglVertex3f(0,1,0)
               vglColor4f(0,1,0,1)
               vglVertex3f(1,-1,0)
               vglColor4f(0,0,1,1)
          vglEnd()
          vglTranslatef(0,0,4)
          vglRotatef(Float(Millisecs())/60,0,1,0)
          vglTranslatef(0,0,4)
     If UsePushPop Then vglPopMatrix()

     For E.Error = Each Error
          Debuglog E\Enum
     Next
     vglFlip()
Until Keyhit(1)

vglQuit()


;;;;; VirtualGL CODE


;VirtualGL is a GL 'simulator' (a laughable concept)
;basically, this tries to mimic the very most basic level of using OpenGL

;no enumerators should resemble the GL enumerators or variables, if they do then it's purely coincedence.
;oh yeah, and no pushing/popping

;currently can only draw triangles and quads, and there're a few useless banks

Type Surface
     Field Texture
     Field Surface[32]
End Type


Type Error
     Field Enum
End Type


Type DisplayList
     Field Offset
     Field Length
End Type


Const VGL_INVALID_ENUM = $E3FAFF01     ;invalid enumerator error
Const VGL_NULL_TEXTURE = $0038AF72     ;null texture- texture not loaded.

;vglBegin enumerators
Const VGL_TRIANGLES% = $00000001
Const VGL_QUADS% = $00000002
Const VGL_TRIANGLE_STRIP% = $00000003
Const VGL_QUAD_STRIP% = $00000004
Const VGL_TRIANGLE_FAN% = $00000005
Const VGL_POINTS% = $00000006
Const VGL_LINES% = $00000007
Const VGL_LINE_STRIP% = $00000008
Const VGL_LINE_LOOP% = $00000009
Const VGL_POLYGON% = $0000000A

;vglEnd enumerators
Global VGL_DRAW_MODE% = 0

;vglEnable / vglDisable enumerators
Const VGL_CULL_FACE = $6A9F0713
Const VGL_AUTO_NORMAL = $FD9F1713
Const VGL_VERTEX_ALPHA = $BAD213FE

;VirtualGL data banks, or databases, take your pick
Global vglCommonData% = 0
Global vglDisplayListData% = 0
Global vglVertexArrayData% = 0

Global vglDisplayMesh

Global NullTexture.Surface
Global vglCurrentTexture.Surface

Global vglBeginOpen = False
Global vglVertexOffset

Global vglViewport

Global vglRotationYaw#,vglRotationPitch#,vglRotationRoll#
Global vglTranslationX#,vglTranslationY#,vglTranslationZ#

Global vglCullFaces = False
Global vglUpdateNormals = False
Global vglVertexAlpha = False

Dim vglStack(0)   ;to me, this is where it gets interesting.
Global vglStackOffset = 0


Function vglInit()
     vglCommonData = CreateBank(0)
     vglDisplayListData = CreateBank(0)
     vglVertexArrayData = CreateBank(0)
     vglDisplayMesh = CreateMesh()
     EntityFX vglDisplayMesh,1+2
     NullTexture.Surface = New Surface
     NullTexture\Surface[vglStackOffset] = CreateSurface(vglDisplayMesh)
     vglCurrentTexture = NullTexture
     vglViewport = CreateCamera()
     CameraClsMode vglViewport,0,1 ;only clear the z buffer

     Dim vglStack(32)
     vglStack(0) = vglDisplayMesh
End Function


Function vglQuit()
     FreeBank vglCommonData
     FreeBank vglDisplayListData
     FreeBank vglVertexArrayData
     FreeEntity vglDisplayMesh
     For S.Surface = Each Surface
          If S\Texture <> 0 Then FreeBrush S\Texture
          Delete S
     Next
End Function


Function vglBegin(VGL_ENUM=0)
     If Not vglCommonData% <> 0 Or vglDisplayListData% <> 0 Or vglVertexArrayData% <> 0 Or vglDisplayMesh <> 0 Then vglError(VGL_NOT_INITIALIZED)
     vglBeginOpen = True
     vglVertexOffset = CountVertices(vglCurrentTexture\Surface[vglStackOffset])
     VGL_DRAW_MODE = VGL_ENUM
End Function


Function vglEnd()
     Select VGL_DRAW_MODE
          Case VGL_TRIANGLES
               N = vglVertexOffset
               While N+2 <= CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1
                    AddTriangle vglCurrentTexture\Surface[vglStackOffset],N,N+1,N+2
                    N = N + 3
               Wend

          Case VGL_QUADS
               N = vglVertexOffset
               While N+3 <= CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1
                    AddTriangle vglCurrentTexture\Surface[vglStackOffset],N,N+1,N+2
                    AddTriangle vglCurrentTexture\Surface[vglStackOffset],N+2,N+3,N
                    N = N + 4
               Wend

          Case VGL_TRIANGLE_STRIP

          Case VGL_QUAD_STRIP

          Case VGL_TRIANGLE_FAN
               N = vglVertexOffset
               While N +2 <= CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1
                    AddTriangle vglCurrentTexture\Surface[vglStackOffset],vglVertexOffset,N+1,N+2
                    N = N + 1
               Wend

          Case VGL_POINTS

          Case VGL_LINES

          Case VGL_LINE_STRIP

          Case VGL_LINE_LOOP

          Case VGL_POLYGON

          Default
               vglError(VGL_INVALID_ENUM)
     End Select

     FreeBank vglCommonData
     vglCommonData = CreateBank()
     VGL_DRAW_MODE = 0
     vglVertexOffset = 0
     vglBeginOpen = False
     vglCurrentTexture = NullTexture
     Return True
End Function


Function vglVertex3f(x#,y#,z#)
     If VGL_DRAW_MODE = 0 Then Return False
     AddVertex(vglCurrentTexture\Surface[vglStackOffset],x,y,z)
End Function


Function vglTexCoord2f(u#,v#)
     If VGL_DRAW_MODE = 0 Or CountVertices(vglCurrentTexture\Surface[vglStackOffset])-vglVertexOffset = 0 Then Return False
     VertexTexCoords vglCurrentTexture\Surface[vglStackOffset],CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1,u,v,0,0
End Function


Function vglNormal3f(nx#,ny#,nz#)
     If VGL_DRAW_MODE = 0 Or CountVertices(vglCurrentTexture\Surface[vglStackOffset])-vglVertexOffset = 0 Then Return False
     VertexNormal vglCurrentTexture\Surface[vglStackOffset],CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1,nx,ny,nz
End Function


Function vglColor4f(r#,g#,b#,a#)
     If VGL_DRAW_MODE = 0 Or CountVertices(vglCurrentTexture\Surface[vglStackOffset])-vglVertexOffset = 0 Then Return False
     VertexColor vglCurrentTexture\Surface[vglStackOffset],CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1,r*255,g*255,b*255,a
End Function


Function vglColor4b(r%,g%,b%,a%)
     If VGL_DRAW_MODE = 0 Or CountVertices(vglCurrentTexture\Surface[vglStackOffset])-vglVertexOffset = 0 Then Return False
     VertexColor vglCurrentTexture\Surface[vglStackOffset],CountVertices(vglCurrentTexture\Surface[vglStackOffset])-1,r,g,b,Float(a)/255
End Function


Function vglFlip()
     EntityFX vglDisplayMesh,1+2+(16*(Not vglCullFaces))+(32*vglVertexAlpha)
     If vglUpdateNormals Then UpdateNormals vglDisplayMesh
     UpdateWorld
     RenderWorld
     Flip False

     For S.Surface = Each Surface
          For N = 0 To 32
               If S\Surface[N] <> 0 Then ClearSurface S\Surface[N],True,True
          Next
     Next
End Function


Function vglError(VGL_ERROR_ENUM)
     E.Error = New Error
     E\Enum = VGL_ERROR_ENUM
End Function


Function vglGetError%()
     E.Error = Last Error
     Error = E\Enum
     Delete E
End Function


Function vglCallList(VGL_LIST.DisplayList)
End Function


Function vglAddVertex()
     ResizeBank vglCommonData,BankSize(vglCommonData)+4*8+2          ;one short, eight floats, in this order: vertex number, x, y, z, normal x, y, z, u, v
     Return BankSize(vglCommonData)-(4*8)-2                           ;it said five previously... old comment.  mistake.
End Function


Function vglLoadTexture(path$,flags=9)
     TEX = LoadBrush(path$,flags)
     If TEX <> 0 Then
          S.Surface = New Surface
          S\Texture = TEX
          S\Surface[0] = CreateSurface(vglDisplayMesh)
          PaintSurface S\Surface[vglStackOffset],S\Texture
          Return Handle(S)
     Endif
     Return 0
End Function


Function vglBindTexture(Tex)     ;unfortunately, i can't simulate the second parameter of glBindTexture 'cause i don't know how to
     Texture.Surface = Object.Surface(Tex)
     If VGL_DRAW_MODE = 0 And Texture <> Null Then
          vglCurrentTexture = Texture.Surface
          If vglCurrentTexture\Surface[vglStackOffset] = 0 Then vglCurrentTexture\Surface[vglStackOffset] = CreateSurface(vglStack(vglStackOffset))
          ;PaintSurface vglCurrentTexture\Surface,vglCurrentTexture\Texture
          Return True
     Endif
     vglError(VGL_NULL_TEXTURE)
     Return False
End Function


Function vglTranslatef(x#,y#,z#)
     vglTranslationX = vglTranslationX + x
     vglTranslationY = vglTranslationY + y
     vglTranslationZ = vglTranslationZ + z
     PositionMesh vglStack(vglStackOffset),x,y,z
End Function


Function vglRotatef(angle#,x#,y#,z#)
     vglRotationPitch# = vglRotationPitch# + angle*x
     vglRotationYaw# = vglRotationYaw# + angle*y
     vglRotationRoll# = vglRotationRoll + angle*z
     RotateMesh vglStack(vglStackOffset),0,0,angle*z
     RotateMesh vglStack(vglStackOffset),angle*x,0,0
     RotateMesh vglStack(vglStackOffset),0,angle*y,0
End Function


Function vglClear(mask)
     Select VGL_ENUM
          Case VGL_COLOR_BUFFER_BIT
               SetBuffer(BackBuffer())
               Cls
          Default
               vglError(VGL_INVALID_ENUM)
     End Select
End Function


Function vglLoadIdentity()
     PositionMesh vglStack(vglStackOffset),-vglTranslationX,-vglTranslationY,-vglTranslationZ
     RotateMesh vglStack(vglStackOffset),-vglRotationPitch,-vglRotationYaw,-vglRotationRoll
     vglTranslationZ = 0 : vglTranslationY = 0 : vglTranslationX = 0
     vglRotationPitch = 0 : vglRotationYaw = 0 : vglRotationRoll = 0
End Function


Function vglEnable(cap)
     Select cap
          Case VGL_AUTO_NORMAL     ;'fraid these are the only really plausible ones to me
               vglUpdateNormals = True

          Case VGL_CULL_FACE
               vglCullFaces = True

          Case VGL_VERTEX_ALPHA
               vglVertexAlpha = True

          Default
               vglError(VGL_INVALID_ENUM)
     End Select
End Function


Function vglDisable(cap)
     Select cap
          Case VGL_AUTO_NORMAL     ;'fraid these are the only really plausible ones to me
               vglUpdateNormals = False

          Case VGL_CULL_FACE
               vglCullFaces = False

          Case VGL_VERTEX_ALPHA
               vglVertexAlpha = False

          Default
               vglError(VGL_INVALID_ENUM)
     End Select
End Function


Function vglPushMatrix() ;a really cheap attempt at push/popping matrices.
     vglStackOffset = vglStackOffset + 1
     If vglStackOffset > 32 Then
          vglQuit()
          RunTimeError "ERROR: vglStackOffset+1 > 32"
     Endif
     vglStack(vglStackOffset) = CreateMesh()
     For S.Surface = Each Surface
          S\Surface[vglStackOffset] = CreateSurface(vglStack(vglStackOffset))
          If S <> NullTexture Then PaintSurface S\Surface[vglStackOffset],S\Texture
     Next
End Function


Function vglPopMatrix()
     If vglStackOffset-1 < 0 Then
          vglQuit()
          RunTimeError "ERROR: vglStackOffset-1 < 0"
     Endif
     AddMesh vglStack(vglStackOffset),vglStack(vglStackOffset-1)
     FreeEntity vglStack(vglStackOffset)
     For S.Surface = Each Surface
          S\Surface[vglStackOffset] = 0
     Next
     vglStackOffset = vglStackOffset - 1
End Function

Comments

Pepsi

2004

Clever & interesting! I had to move the globals above the main loop though because vglcurrenttexture is defined below that in which errored on me. No biggy though. Cool!

Pepsi

2004

lol... are you testing your code before you sumbit it? In your main loop you have some gl functions that need the character ' v ' in front of them so it wont error out. :)

The quad and triangle do get textured for me when I use my own texture in the "PART_FIRE.Surface = vglLoadTexture("part_fire.tga",1+2)" line.

2004

Seems I had Insert on when I commented those function calls- uncommented them when posting the example- stupid mistake >_<

Thanks for pointing that out :P

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