;;; Chickadee Game Toolkit
;;; Copyright © 2019, 2021 David Thompson <davet@gnu.org>
;;;
;;; Chickadee 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.
;;;
;;; Chickadee 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:
;;
;; Simple forward rendered Phong lighting model.
;;
;;; Code:

(define-module (chickadee graphics phong)
  #:use-module (chickadee config)
  #:use-module (chickadee math vector)
  #:use-module (chickadee graphics blend)
  #:use-module (chickadee graphics color)
  #:use-module (chickadee graphics depth)
  #:use-module (chickadee graphics engine)
  #:use-module (chickadee graphics light)
  #:use-module (chickadee graphics mesh)
  #:use-module (chickadee graphics polygon)
  #:use-module (chickadee graphics shader)
  #:use-module (chickadee graphics stencil)
  #:use-module (chickadee graphics texture)
  #:use-module (srfi srfi-9)
  #:export (make-phong-properties
            phong-properties?
            phong-properties-ambient
            phong-properties-diffuse
            phong-properties-specular
            phong-properties-shininess
            phong-shader
            make-phong-material))

(define-shader-type <phong-properties>
  make-phong-properties
  phong-properties?
  (float-vec3 ambient phong-properties-ambient)
  (float-vec3 diffuse phong-properties-diffuse)
  (float-vec3 specular phong-properties-specular)
  (float shininess phong-properties-shininess))

(define %phong-shader
  (delay (load-shader (scope-datadir "shaders/phong-vert.glsl")
                      (scope-datadir "shaders/phong-frag.glsl"))))

(define (phong-shader)
  (force %phong-shader))

(define* (make-phong-material #:key (name "anonymous")
                              (blend-mode blend:replace)
                              (polygon-mode fill-polygon-mode)
                              (cull-face-mode back-cull-face-mode)
                              (depth-test basic-depth-test)
                              (stencil-test default-stencil-test)
                              multisample?
                              (ambient-factor (vec3 1.0 1.0 1.0))
                              (diffuse-factor (vec3 1.0 1.0 1.0))
                              (specular-factor (vec3 1.0 1.0 1.0))
                              (shininess 32.0)
                              (ambient-texture (white-texture))
                              (diffuse-texture (white-texture))
                              (specular-texture (white-texture))
                              (normal-texture (flat-texture)))
  (make-material #:name name
                 #:shader (phong-shader)
                 #:texture-0 ambient-texture
                 #:texture-1 diffuse-texture
                 #:texture-2 specular-texture
                 #:texture-3 normal-texture
                 #:properties (make-phong-properties #:ambient ambient-factor
                                                     #:diffuse diffuse-factor
                                                     #:specular specular-factor
                                                     #:shininess shininess)))