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;;; Sly
;;; Copyright (C) 2014 David Thompson <davet@gnu.org>
;;;
;;; Sly is free software: you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; Sly is distributed in the hope that it will be useful, but WITHOUT
;;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
;;; or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
;;; License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Vertex arrays encapsulate the geometry for a single OpenGL draw
;; call.
;;
;;; Code:
(define-module (sly render vertex-array)
#:use-module (system foreign)
#:use-module (ice-9 match)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-43)
#:use-module (rnrs bytevectors)
#:use-module (gl)
#:use-module (gl low-level)
#:use-module (sly wrappers gl)
#:use-module (sly math vector)
#:use-module (sly color)
#:use-module (sly shader)
#:export (make-vertex-array
vertex-array?
vertex-array-id vertex-array-length
apply-vertex-array with-vertex-array))
;;;
;;; Vertex Buffers
;;;
(define-record-type <vertex-buffer>
(%make-vertex-buffer id type attr-size length)
vertex-buffer?
(id vertex-buffer-id)
(type vertex-buffer-type)
(attr-size vertex-buffer-attr-size)
(length vertex-buffer-length))
(define (generate-vertex-buffer)
(let ((bv (u32vector 1)))
(glGenBuffers 1 (bytevector->pointer bv))
(u32vector-ref bv 0)))
(define (bind-vertex-buffer vbo)
(glBindBuffer (vertex-buffer-type vbo)
(vertex-buffer-id vbo)))
(define-syntax-rule (with-vertex-buffer vbo body ...)
(let ((type (vertex-buffer-type vbo)))
(glBindBuffer type (vertex-buffer-id vbo))
body ...
(glBindBuffer type 0)))
(define (vertices-bytevector vertices index?)
(let* ((elem (vector-ref vertices 0))
(bv (if index?
(make-u32vector (vector-length vertices))
(make-f32vector (* (vector-length vertices)
(attribute-size elem)))))
(setter (if index? u32vector-set! f32vector-set!)))
(vector-for-each
(match-lambda*
((i (? number? k))
(setter bv i k))
((i ($ <vector2> x y))
(let ((offset (* i 2)))
(setter bv offset x)
(setter bv (1+ offset) y)))
((i ($ <vector3> x y z))
(let ((offset (* i 3)))
(setter bv offset x)
(setter bv (1+ offset) y)
(setter bv (+ offset 2) z)))
((i ($ <vector4> x y z w))
(let ((offset (* i 4)))
(setter bv offset x)
(setter bv (1+ offset) y)
(setter bv (+ offset 2) z)
(setter bv (+ offset 3) w)))
((i (color? c))
(let ((offset (* i 4)))
(setter bv offset (color-r c))
(setter bv (1+ offset) (color-g c))
(setter bv (+ offset 2) (color-b c))
(setter bv (+ offset 3) (color-a c)))))
vertices)
bv))
(define attribute-size
(match-lambda
((? number? _) 1)
((? vector2? _) 2)
((? vector3? _) 3)
((or (? vector4? _)
(? color? _))
4)
(attr
(error "Unsupported vertex buffer attribute: " attr))))
(define (gl-buffer-type index?)
(if index?
(arb-vertex-buffer-object element-array-buffer-arb)
(arb-vertex-buffer-object array-buffer-arb)))
(define* (make-vertex-buffer vertices #:optional (index? #f))
(let ((bv (vertices-bytevector vertices index?))
(vbo (%make-vertex-buffer (generate-vertex-buffer)
(gl-buffer-type index?)
(attribute-size (vector-ref vertices 0))
(vector-length vertices))))
(with-vertex-buffer vbo
(glBufferData (vertex-buffer-type vbo)
(bytevector-length bv)
(bytevector->pointer bv)
(arb-vertex-buffer-object static-draw-arb)))
vbo))
;;;
;;; Vertex Arrays
;;;
(define-record-type <vertex-array>
(%make-vertex-array id length)
vertex-array?
(id vertex-array-id)
(length vertex-array-length))
(define (generate-vertex-array)
(let ((bv (u32vector 1)))
(glGenVertexArrays 1 (bytevector->pointer bv))
(u32vector-ref bv 0)))
(define (apply-vertex-array vao)
(glBindVertexArray (vertex-array-id vao)))
(define-syntax-rule (with-vertex-array vao body ...)
(begin
(apply-vertex-array vao)
body ...
(glBindVertexArray 0)))
(define (vertex-attrib-pointer location vbo)
(glEnableVertexAttribArray location)
(with-vertex-buffer vbo
(glVertexAttribPointer location (vertex-buffer-attr-size vbo)
(data-type float) #f 0 %null-pointer)))
(define (make-vertex-array indices positions textures)
(let ((vao (%make-vertex-array (generate-vertex-array)
(vector-length indices)))
(positions (make-vertex-buffer positions))
(textures (make-vertex-buffer textures)))
(with-vertex-array vao
(vertex-attrib-pointer vertex-position-location positions)
(if textures
(vertex-attrib-pointer vertex-texture-location textures))
(bind-vertex-buffer (make-vertex-buffer indices #t)))
vao))
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