;;; Sly
;;; Copyright (C) 2014 David Thompson <davet@gnu.org>
;;;
;;; This program 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.
;;;
;;; This program 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:
;;
;; Primitive 2D/3D shapes.
;;
;;; Code:

(define-module (sly render shape)
  #:use-module (sly math)
  #:use-module (sly render)
  #:use-module (sly render mesh)
  #:use-module (sly render texture)
  #:use-module (sly math vector)
  #:export (make-cube))

;; TODO: Write some combinators for composing triangles into more
;; complex shapes with a procedure to convert them into a mesh.

(define* (make-cube size #:optional #:key (texture #f))
  (let* ((half-size (half size))
         (mesh (build-mesh #(
                             ;; Front
                             0 3 2 0 2 1
                               ;; Back
                               4 6 7 4 5 6
                               ;; Top
                               8 11 10 8 10 9
                               ;; Bottom
                               12 14 15 12 13 14
                               ;; Left
                               16 19 18 16 18 17
                               ;; Right
                               20 22 23 20 21 22)
                           (vector
                            ;; Front
                            (vector3 (- half-size) (- half-size) (- half-size))
                            (vector3 half-size (- half-size) (- half-size))
                            (vector3 half-size half-size (- half-size))
                            (vector3 (- half-size) half-size (- half-size))
                            ;; Back
                            (vector3 (- half-size) (- half-size) half-size)
                            (vector3 half-size (- half-size) half-size)
                            (vector3 half-size half-size half-size)
                            (vector3 (- half-size) half-size half-size)
                            ;; Top
                            (vector3 (- half-size) half-size (- half-size))
                            (vector3 half-size half-size (- half-size))
                            (vector3 half-size half-size half-size)
                            (vector3 (- half-size) half-size half-size)
                            ;; Bottom
                            (vector3 (- half-size) (- half-size) (- half-size))
                            (vector3 half-size (- half-size) (- half-size))
                            (vector3 half-size (- half-size) half-size)
                            (vector3 (- half-size) (- half-size) half-size)
                            ;; Left
                            (vector3 (- half-size) (- half-size) (- half-size))
                            (vector3 (- half-size) half-size (- half-size))
                            (vector3 (- half-size) half-size half-size)
                            (vector3 (- half-size) (- half-size) half-size)
                            ;; Right
                            (vector3 half-size (- half-size) (- half-size))
                            (vector3 half-size half-size (- half-size))
                            (vector3 half-size half-size half-size)
                            (vector3 half-size (- half-size) half-size))
                           (let ((s1 (texture-s1 texture))
                                 (t1 (texture-t1 texture))
                                 (s2 (texture-s2 texture))
                                 (t2 (texture-t2 texture)))
                             (vector
                              ;; Front
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2)
                              ;; Back
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2)
                              ;; Top
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2)
                              ;; Bottom
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2)
                              ;; Left
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2)
                              ;; Right
                              (vector2 s1 t1)
                              (vector2 s2 t1)
                              (vector2 s2 t2)
                              (vector2 s1 t2))))))
    (with-texture texture
      (render-mesh mesh))))