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Lispified the first tutorial. Works well!
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@cbaggers
cbaggers committed Jun 8, 2012
1 parent 6421267 commit 7001ff2
Showing 1 changed file with 39 additions and 108 deletions.
147 changes: 39 additions & 108 deletions arc-tuts/arc-tut-1.lisp
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;;; our libraries work well enough.
;;; Many comments may be taken from the tutorials to spare
;;; my terrible memory

;;; this version is going to be tidied using the lispy
;;; abstractions provided by the cl-eopgl and glut libraries
(in-package :cepl)

;;;--------------------------------------------------------------
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error-string))))
shader))


(defun make-program (shaders)
(let ((program (gl:create-program)))
(loop for shader in shaders
Expand All @@ -44,6 +48,7 @@
do (gl:detach-shader program shader))
program))


(defun shader-type-from-path (path)
"This uses the extension to return the type of the shader"
(let* ((plen (length path))
Expand All @@ -53,9 +58,9 @@
(t (error "Could not extract shader type from shader"))
)))

(defun initialize-program ()
(let* ((shader-paths `("./tut1.vert" "./tut1.frag"))
(shaders (mapcar (lambda (path)

(defun initialize-program (shader-paths)
(let* ((shaders (mapcar (lambda (path)
(make-shader
path
(shader-type-from-path path)))
Expand All @@ -65,30 +70,11 @@
do (gl:delete-shader shader))
program))

;;;--------------------------------------------------------------

;; A vertex is a collection of arbitrary data. For the sake of
;; simplicity (we will expand upon this later), let us say
;; that this data must contain a point in three dimensional
;; space.
(defstruct vertex
position)

;; note that these co-ords are already in clip space
(defparameter *vertex-positions* #(-0.75 0.75 0.0 1.0
0.0 0.0 0.0 1.0
-0.75 -0.75 0.0 1.0))

(defparameter *program-id* nil)
(defparameter *position-buffer-object* nil)

;;;--------------------------------------------------------------


(defun setup-buffer (buf-type data-type data)
(let* ((data-length (length data))
(arr (gl:alloc-gl-array data-type data-length))
(buffer (car (gl:gen-buffers 1))))
;; need to pass data as a c-array
(dotimes (i data-length)
(setf (gl:glaref arr i) (aref data i)))
(gl:bind-buffer buf-type buffer)
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;;;--------------------------------------------------------------

(defun init ()
(setf *program-id* (initialize-program))
(setf *position-buffer-object* (initialize-vertex-buffer)))

(defun initialize-vertex-buffer ()
;; * creates a buffer
;; * binds the buffer to array-buffer binding target, this
;; gives the buffer context in opengl
;; * gl:buffer-data does a few things
;; - state that we are pushing to the currently bound
;; array-buffer
;; - allocate and push the data from *vertex-positions*
;; - set as :static-draw.... this we come to in future
;; tutorials
;; * cleanup the data we have used
;; so we have populated (as far as opengl is concerned) a
;; load of random binary data, we tell opengl how to use it
;; in the rendering code
(setup-buffer :array-buffer
:float
*vertex-positions*))

;;;--------------------------------------------------------------

(cffi:defcallback display :void ()
;; this is a state setting function, its sets the color used
;; when clearing the screen
(defclass arc-tut-window (glut:window)
((vbuff :accessor vertex-buffer)
(va :accessor vertex-array)
(program :accessor program))
(:default-initargs :width 500 :height 500 :pos-x 100
:pos-y 100
:mode `(:double :alpha :depth :stencil)
:title "ArcSynthesis Tut 1"))


(defmethod glut:display-window :before ((win arc-tut-window))
(setf (program win) (initialize-program
`("./tut1.vert" "./tut1.frag"))
(vertex-array win) #(-0.75 0.75 0.0 1.0
0.0 0.0 0.0 1.0
-0.75 -0.75 0.0 1.0)
(vertex-buffer win) (setup-buffer :array-buffer
:float
(vertex-array win))))

(defmethod glut:display ((win arc-tut-window))
(gl:clear-color 0.0 0.0 0.0 0.0)
;; here we are using clearing the color buffer
(gl:clear :color-buffer-bit)
;; sets the shader program to be used in all the following
;; commands we will need to wrap this up in a 'with-program'
;; macro.
(gl:use-program *program-id*)
;; bind position-buffer-object to the array-buffer
;; tell opengl where the co-ords of the triangle we want to
;; draw are
(gl:bind-buffer :array-buffer *position-buffer-object*)
;; this enables the attribute index we will use for the
;; position attribute.
(gl:use-program (program win))
(gl:bind-buffer :array-buffer (vertex-buffer win))

(gl:enable-vertex-attrib-array 0)
;; the following is not abount pointers, its abount gl-objects
;; it's laid out as follows
;; * attribute index
;; * num of vals per piece of data
;; * val type
;; * ?
;; * spacing beween each set of values
;; * specifies the offset to the first piece of data
;; remeber this is acting on the currently bound buffer
(gl:vertex-attrib-pointer 0 4 :float :false
0 (cffi:null-pointer))
;; The glDrawArrays function is, as the name suggests, a
;; rendering function. It uses the current state to generate
;; a stream of vertices that will form triangles.
;; the 0 specifies the first index (refering to data specified
;; in vertex-attrib-pointer) and the number of vertices to
;; read (3).
(gl:draw-arrays :triangles 0 3)
;; unbind things
(gl:disable-vertex-attrib-array 0)
(gl:use-program 0)
;; swap the buffer to make what we have drawn visible
(glut:swap-buffers))

(cffi:defcallback reshape :void ((width :int) (height :int))
(let ((dim (min width height)))
(gl:viewport 0 0 width height)))
(defmethod glut:reshape ((win arc-tut-window) width height)
(gl:viewport 0 0 width height))

;; The only reason the print statements are there is so I dont
;; get style warnings
(cffi:defcallback keyboard :void ((key :char) (x :int) (y :int))
(defmethod glut:keyboard ((win arc-tut-window) key x y)
(declare (ignore x y))
(if (eql key 27)
(glut:leave-main-loop)))

;;;--------------------------------------------------------------
(case key
(#\Esc (glut:destroy-current-window))))

(defun run-demo ()
(let ((width 500)
(height 500))
(glut:init)
(glut:init-display-mode :double :alpha :depth :stencil)
(glut:init-window-size width height)
(glut:create-window "ArcSynthesis Tutorial 1")
(init) ; to initialise the data
(glut:display-func (cffi:callback display))
(glut:reshape-func (cffi:callback reshape))
(glut:keyboard-func (cffi:callback keyboard))
(glut:main-loop)))


;; could be useful later, who knows.
;; (if debug-arb
;; (progn (gl:enable :debug-output-synchronous-arb)
;; (gl:debug-message-callback-arb (cffi:callback debug) 15)))



(glut:display-window (make-instance 'arc-tut-window)))

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