Tutorials for 2D OpenGL

Lster · Post by **Lster** » Oct 20, 2006 14:06

I am wondering if OpenGL has libraries and functions for 2D drawing like (line, circle etc...). (Ive used OpenGL for 3D a bit though.) If so... anyone know a good tutorial on the internet?

Thanks,
Lster

ikkejw · Post by **ikkejw** » Oct 20, 2006 14:31

I'm working on a lib which can do line, put, circle etc in OpenGL :) so you don't need to do it yourself.

I haven't finished it yet, but as soon as I got rid of this bug, I will post it in the Projects forum.

1000101 · Post by **1000101** » Oct 20, 2006 14:33

OpenGL can naitively do points, lines, line loops, triangles and triangle strips.

From these, you can make other primitives such as circles, rectangles, n-gons, etc. There are lots of examples on the web. Try google, it's a good source.

D.J.Peters · Post by **D.J.Peters** » Oct 20, 2006 18:53

The best 2D OpenGl FreeBASIC tutorial are from stormy.
http://other.storm-master.de/ogl/index.html
It's in german but if you take a look on the pictures and line of codes
i'm sure you will find it usefull too.

Can be that the translation in english are in progress please ask stormy about that.

Joshy

TbbW · Post by **TbbW** » Oct 21, 2006 19:06

Argh!
an tutorial made in a diffrent language... lucky germans, poor non germans.

D.J.Peters · Post by **D.J.Peters** » Oct 21, 2006 20:11

TbbW wrote:Argh!
an tutorial made in a diffrent language... lucky germans, poor non germans.

The best and only FreeBASIC 2D OpenGl tutorial.

Joshy

TbbW · Post by **TbbW** » Oct 21, 2006 23:02

mjeah... babelfish got owned by that page...
google translation translated good but only half the page.
( but google #%$@ up the blocks with code in em... the linefeed got removed for some odd reson )

someone who knows german suld translate that page and source comments.

hartnell · Post by **hartnell** » Oct 21, 2006 23:20

You might get some insights on using OpenGL with FreeBASIC by checking out Basic4GL. It's not FreeBASIC, but it's a BASIC dialect that has OpenGL support built in.

You also might want to consider using Allegro rather than OpenGL.

-hartnell

JohnB · Post by **JohnB** » Oct 22, 2006 2:24

Translated version.

Go to Google, type in search "storm-master ogl"

find link for site, click on "translate this page"

Very nice tutorial.

JohnB

Lster · Post by **Lster** » Oct 22, 2006 9:16

Thanks everyone for your help... Nows the hard bit: learning OpenGL...

Lster · Post by **Lster** » Oct 29, 2006 12:48

Ive been following the tutorial by Stormy, which is very good. Although the translation by Google is bad.

Anyway, without using any other libraries, how can I use textures.

Code: Select all

#include once "GL/gl.bi"
#include once "GL/glu.bi"
#include "inc/2d_opengl.bi"

screen 20, 32, , &h2 OR &h1

glMatrixMode(GL_PROJECTION)
glLoadIdentity()
glViewport(0.0, 0.0, 1024, 768)
glOrtho(0, 1024, 768, 0, -128, 128)
glMatrixMode(GL_MODELVIEW)
glEnable(GL_CULL_FACE)
glCullFace(GL_BACK)
glEnable(GL_TEXTURE_2D)
glLoadIdentity()

glDepthFunc(GL_LESS)
glEnable(GL_ALPHA_TEST)
glAlphaFunc(0, 1)

' Load texture

do
    glClear(GL_COLOR_BUFFER_BIT OR GL_DEPTH_BUFFER_BIT)
    
    glBindTexture GL_TEXTURE_2D, texture
    glBegin GL_QUADS
        glTexCoord2f 0, 0
        glVertex2i 0, 32
        
        glTexCoord2f 1, 0
        glVertex2i 32, 32
        
        glTexCoord2f 1, 1
        glVertex2i 32, 0
        
        glTexCoord2f 0, 1
        glVertex2i 0, 0
    glEnd
    
    flip
    screenSync
loop until multikey(&h1)

Thanks,
Lster

1000101 · Post by **1000101** » Oct 29, 2006 17:39

Well, you need to load a texture and tell GL about it.

The easiest method is to use the CreateTexture function from lillo.

Code: Select all

'lillo
Function CreateTexture( Byval buffer As Any Ptr, Byval flags As Integer = 0 ) As GLuint
                Redim dat(0) As Uinteger
                Dim p As Uinteger Ptr
                Dim As Integer w, h, x, y, col
                Dim tex As GLuint
                Dim As GLenum format, minfilter, magfilter
                
                CreateTexture = 0
                
                w = cptr(Short Ptr, buffer)[0] Shr 3
                h = cptr(Short Ptr, buffer)[1]
                
                If( (w < 64) Or (h < 64) ) Then
                        End -11'Exit Function
                End If
                If( (w And (w-1)) Or (h And (h-1)) ) Then
                        'Width/height not powers of 2
            'Exit Function
            End -12
                End If
                
                Redim Dat(w * h) As Uinteger
                p = @Dat(0)
                
                glGenTextures 1, @tex
                glBindTexture GL_TEXTURE_2D, tex
                
                For y = h-1 To 0 Step -1
                        For x = 0 To w-1
                                col = Point(x, y, buffer)
                                '' Swap R and B so we can use the GL_RGBA texture format
                                col = RGBA(col And &hFF, (col Shr 8) And &hFF, (col Shr 16) And &hFF, col Shr 24)
                
                If( flags And TEX_HASALPHA ) Then
                                        *p = col
                                Else
                                        If( (flags And TEX_MASKED) And (col = &hFF00FF) ) Then
                                                *p = 0
                                        Else
                                                *p = col Or &hFF000000
                                        End If
                                End If
                                p += 1
                        Next x
                Next y
                
                If( flags And ( TEX_MASKED Or TEX_HASALPHA ) ) Then
                        format = GL_RGBA
                Else
                        format = GL_RGB
                End If
                
                If( flags And TEX_NOFILTER ) Then
                        magfilter = GL_NEAREST
                Else
                        magfilter = GL_LINEAR
                End If
                
                If( flags And TEX_MIPMAP ) Then
                        gluBuild2DMipmaps GL_TEXTURE_2D, format, w, h, GL_RGBA, GL_UNSIGNED_BYTE, @dat(0)
                        If( flags And TEX_NOFILTER ) Then
                                minfilter = GL_NEAREST_MIPMAP_NEAREST
                        Else
                                minfilter = GL_LINEAR_MIPMAP_LINEAR
                        End If
                Else
                        glTexImage2D GL_TEXTURE_2D, 0, format, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, @dat(0)
                        minfilter = magfilter
                End If
                glTexParameteri GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minfilter
                glTexParameteri GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magfilter
                
                CreateTexture = tex
        
End Function

cha0s · Post by **cha0s** » Oct 30, 2006 3:41

doesn't that only work with old style buffers?

1000101 · Post by **1000101** » Oct 30, 2006 3:54

hrm, it does need to be updated, doesn't it?

Try this instead, works with the old and new buffers.

Code: Select all

#Define   TEX_MASKED           &h1
#Define   TEX_MIPMAP           &h2
#Define   TEX_NOFILTER         &h4
#Define   TEX_HASALPHA         &h8




#IfNDef _OLD_HEADER
type _OLD_HEADER field = 1
	bpp : 3 as ushort
	width : 13 as ushort
	height as ushort
end type
#EndIf




#IfNDef PUT_HEADER
type PUT_HEADER field = 1
	union
		old as _OLD_HEADER
		type as uinteger
	end union
	bpp as integer
	width as uinteger
	height as uinteger
	pitch as uinteger
	_reserved(1 to 12) as ubyte
end type
#EndIf




#IfNDef PUT_HEADER_NEW
#define PUT_HEADER_NEW		&h7
#EndIf




Function CreateTexture _
   (	_
   Byval Buffer As PUT_HEADER Ptr       , _
   Byval Flags  As Uinteger       = NULL  _
   ) As GLuint
   
   
   Redim As Uinteger           dat( 0 )
   Dim As Uinteger Ptr         pPixels
   Dim As Integer              w, h, x, y, col, i
   Dim As GLuint               rTex
   Dim As GLenum               format, minfilter, magfilter
   
   
   If ( Buffer->Type = PUT_HEADER_NEW ) Then
      
      w = Buffer->Width
      h = Buffer->Height
      
   Else
      
      w = Buffer->Old.Width
      h = Buffer->Old.Height
      
   End If
   
   
   If ( ( w < 8 ) Or ( h < 8 ) ) Then AbortCode( ERROR_TEXTURE Or ERROR_BAD_SIZE, TextureCreate_Abort )
   If ( ( w And ( w - 1 ) ) Or ( h And ( h - 1 ) ) ) Then AbortCode( ERROR_TEXTURE Or ERROR_BAD_SIZE, TextureCreate_Abort )
   
   Redim As Uinteger           dat( w * h )
   pPixels = @dat( 0 )
   
   
   glGenTextures       1, @rTex
   AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
   
   glBindTexture       GL_TEXTURE_2D, rTex
   AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
   
   
   i = 0
   For y = ( h - 1 ) To 0 Step -1
      For x = 0 To ( w - 1 )
         
         col = Point( x, y, Buffer )
         
         col = BGRA_To_RGBA( col )
         
         If ( Flags And TEX_HASALPHA ) Then
            pPixels[ i ] = col
         Else
            If ( ( Flags And TEX_MASKED ) And ( ( col And &HFFFFFF ) = &hFF00FF ) ) Then
               pPixels[ i ] = 0
            Else
               pPixels[ i ] = col Or &hFF000000
            End If
         End If
         
         i += 1
         
      Next x
   Next y
   
   
   If ( Flags And ( TEX_MASKED Or TEX_HASALPHA ) ) Then
      format = GL_RGBA
   Else
      format = GL_RGB
   End If
   
   
   If ( Flags And TEX_NOFILTER ) Then
      magfilter = GL_NEAREST
   Else
      magfilter = GL_LINEAR
   End If
   
   
   If ( Flags And TEX_MIPMAP ) Then
      
      gluBuild2DMipmaps GL_TEXTURE_2D, format, w, h, GL_RGBA, GL_UNSIGNED_BYTE, pPixels
      AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
      
      If ( Flags And TEX_NOFILTER ) Then
         minfilter = GL_NEAREST_MIPMAP_NEAREST
      Else
         minfilter = GL_LINEAR_MIPMAP_LINEAR
      End If
      
   Else
      
      glTexImage2D GL_TEXTURE_2D, 0, format, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, pPixels
      AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
      
      minfilter = magfilter
      
   End If
   
   
   glTexParameteri GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minfilter
   AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
   glTexParameteri GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magfilter
   AbortGL( ERROR_TEXTURE, TextureCreate_Abort, __LINE__ )
   
   
   Return rTex
   
   
   TextureCreate_Abort:
   
   
   If ( rTex ) Then glDeleteTextures 1, @rTex
   
   Return NULL
   
   
End Function

Edit: Added in checks for structures for older versions of fb so they won't puke.

Lster · Post by **Lster** » Oct 30, 2006 13:10