[plt-scheme] OpenGL and GLUT

I found 'alpha.ss' a helpful example


Stephen


#lang scheme/gui
;; By Brendan Burns
;; on Jaunty install the libgl1-mesa-dev package or make the symbolic links
yourself
;; /usr/lib$ sudo ln -s libGL.so.1 libGL.so
;; /usr/lib$ sudo ln -s libGLU.so.1 libGLU.so

;; Standard requires
(require
 sgl/gl
 "gl-frame.ss")

;; texture
;; This needs to be here and not in gl-init because of some weirdness in the
;; threading on windows causes the window to attempt to be drawn prior to
the
; texture being fully loaded.
(define *texture* (image->gl-vector (get-file "Choose image for texture" #f
"../../icons" "sk" "jpg" null '(("Image" "*.jpg")))))

;; Init function
(define (my-gl-init)
  (let ((res *texture*))
    ;; Same texture, three smoothing styles...
    (init-textures 3)
    (unless (gl-load-texture (list-ref res 2) (list-ref res 0) (list-ref res
1)
                            GL_NEAREST GL_NEAREST 0)
      (error "Couldn't load texture"))
    (unless (gl-load-texture (list-ref res 2) (list-ref res 0) (list-ref res
1)
                            GL_LINEAR GL_LINEAR 1)
      (error "Couldn't load texture"))
    (unless (gl-load-texture (list-ref res 2) (list-ref res 0) (list-ref res
1)
                            GL_LINEAR GL_LINEAR_MIPMAP_NEAREST 2)
      (error "Couldn't load texture"))

    ;; Set-up alpha blending 50% transparency
    (glColor4d 1 1 1 0.5)
    (glBlendFunc GL_SRC_ALPHA GL_ONE)
    (glEnable GL_BLEND)

    ;; Standard Init
    (glEnable GL_TEXTURE_2D)
    (glShadeModel GL_SMOOTH)
    (glClearColor 0.0 0.0 0.0 0.5)
    (glClearDepth 1)
    (glEnable GL_DEPTH_TEST)
    (glDepthFunc GL_LEQUAL)
    (glHint GL_PERSPECTIVE_CORRECTION_HINT GL_NICEST)

    ;; default light
    (glEnable GL_LIGHT0)
    (glEnable GL_LIGHTING)))

;; Our user interaction variables
(define *xrot* 0)
(define *yrot* 0)
(define *zrot* 0)
(define *z* -5)
(define *blend* #f)
(define *tex* 0)

;; Our main function that does the drawing
(define (my-gl-draw)
  ;; erase the background
  (glClear (+ GL_COLOR_BUFFER_BIT GL_DEPTH_BUFFER_BIT))
  ;; turn blending on/off
  (if *blend* (glEnable GL_BLEND) (glDisable GL_BLEND))

  ;; draw cube.
  (glLoadIdentity)
  (glTranslated 0 0 *z*)
  (glRotated *xrot* 1 0 0)
  (glRotated *yrot* 0 1 0)
  (glRotated *zrot* 0 0 1)
  (glBindTexture GL_TEXTURE_2D (get-texture *tex*))
  (glBegin GL_QUADS)
  ; front
  (glNormal3d 0 0 1)
  (glTexCoord2i 0 0)
  (glVertex3i -1 -1 1)
  (glTexCoord2i 1 0)
  (glVertex3i 1 -1 1)
  (glTexCoord2i 1 1)
  (glVertex3i 1 1 1)
  (glTexCoord2i 0 1)
  (glVertex3i -1 1 1)
  ; back
  (glNormal3d 0 0 -1)
  (glTexCoord2i 1 0)
  (glVertex3i -1 -1 -1)
  (glTexCoord2i 1 1)
  (glVertex3i 1 -1 -1)
  (glTexCoord2i 0 1)
  (glVertex3i 1 1 -1)
  (glTexCoord2i 0 0)
  (glVertex3i -1 1 -1)
  ; top
  (glNormal3d 0 1 0)
  (glTexCoord2i 0 1)
  (glVertex3i -1 1 -1)
  (glTexCoord2i 0 0)
  (glVertex3i 1 1 -1)
  (glTexCoord2i 1 0)
  (glVertex3i 1 1 1)
  (glTexCoord2i 1 1)
  (glVertex3i -1 1 1)
  ; bottom
  (glNormal3d 0 -1 0)
  (glTexCoord2i 1 1)
  (glVertex3i -1 -1 -1)
  (glTexCoord2i 0 1)
  (glVertex3i -1 -1 1)
  (glTexCoord2i 0 0)
  (glVertex3i 1 -1 1)
  (glTexCoord2i 1 0)
  (glVertex3i 1 -1 -1)
  ; right
  (glNormal3d 1 0 0)
  (glTexCoord2i 1 0)
  (glVertex3i 1 -1 -1)
  (glTexCoord2i 1 1)
  (glVertex3i 1 -1 1)
  (glTexCoord2i 0 1)
  (glVertex3i 1 1 1)
  (glTexCoord2i 0 0)
  (glVertex3i 1 1 -1)
  ;left
  (glNormal3d -1 0 0)
  (glTexCoord2i 0 0)
  (glVertex3i -1 -1 -1)
  (glTexCoord2i 1 0)
  (glVertex3i -1 1 -1)
  (glTexCoord2i 1 1)
  (glVertex3i -1 1 1)
  (glTexCoord2i 0 1)
  (glVertex3i -1 -1 1)

  (glEnd)
  (set! *xrot* (+ *xrot* 0.3))
  (set! *yrot* (+ *yrot* 0.2))
  (set! *zrot* (+ *zrot* 0.4))

  (glFlush))

;; Move forward
(add-key-mapping #\i (lambda () (set! *z* (+ *z* 0.3))))
;; Move backward
(add-key-mapping #\k (lambda () (set! *z* (- *z* 0.3))))
;; Turn blending on/off
(add-key-mapping #\b (lambda () (set! *blend* (not *blend*))))
;; Cycle textures
(add-key-mapping #\t (lambda () (set! *tex* (modulo (+ *tex* 1) 3))))

;; Set the init function
(set-gl-init-fn my-gl-init)
;; Set the draw function
(set-gl-draw-fn my-gl-draw)
(gl-run)


On Mon, Jan 18, 2010 at 7:50 PM, Eduardo Bellani <ebellani at gmail.com> wrote:

> > First, some of the GLUT functions are implemented in the sgl library.
> > Search for glu on the C style API page.
> >
> > It seems like you're main problem is starting up a canvas and getting
> > a GL-context.
> >
> > Attached is a short example with your code based on my gl-world package.
> >
> > Jay
> Thanks man!
>
> Now I do have a working canvas, at least.
>
> Do you have any clue as to why
> it does not visible draw anything? From what I'm seeing, the C and the
> scheme
> versions are somewhat equivalent, except for the resize and all the GLUT
> calls.
>
>
> --
> Eduardo Bellani
>
> www.cnxs.com.br
>
> More is not better (or worse) than less, just different.
> – The paradigm paradox.
> _________________________________________________
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>



-- 

--
Stephen De Gabrielle
stephen.degabrielle at acm.org
Telephone +44 (0)20 85670911
Mobile        +44 (0)79 85189045
http://www.degabrielle.name/stephen
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