From 662d04ffa53f9c400d959ceeb9af9a7bb9ad63cf Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 12 May 2021 20:43:45 -0400
Subject: Add (chickadee graphics light) module.

---
 Makefile.am                  |   1 +
 chickadee/graphics/light.scm | 103 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 chickadee/graphics/light.scm

diff --git a/Makefile.am b/Makefile.am
index be0f917..4b5d802 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -80,6 +80,7 @@ SOURCES = 					\
   chickadee/graphics/font.scm			\
   chickadee/graphics/tile-map.scm		\
   chickadee/graphics/particles.scm		\
+  chickadee/graphics/light.scm			\
   chickadee/graphics/phong.scm			\
   chickadee/graphics/pbr.scm			\
   chickadee/graphics/model.scm			\
diff --git a/chickadee/graphics/light.scm b/chickadee/graphics/light.scm
new file mode 100644
index 0000000..d217f56
--- /dev/null
+++ b/chickadee/graphics/light.scm
@@ -0,0 +1,103 @@
+;;; Chickadee Game Toolkit
+;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
+;;;
+;;; 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:
+;;
+;; 3D lights.
+;;
+;;; Code:
+
+(define-module (chickadee graphics light)
+  #:use-module (chickadee graphics color)
+  #:use-module (chickadee graphics shader)
+  #:use-module (chickadee math)
+  #:use-module (chickadee math vector)
+  #:export (%max-lights
+            make-point-light
+            make-directional-light
+            make-spot-light
+            %disabled-light
+            light?
+            point-light?
+            directional-light?
+            spot-light?
+            light-enabled?
+            light-type
+            light-position
+            light-direction
+            light-color
+            light-cut-off
+            set-light-position!
+            set-light-direction!
+            set-light-color!
+            set-light-cut-off!))
+
+;; Maximum number of lights supported by our shaders.
+(define %max-lights 4)
+
+(define-shader-type <light>
+  make-light
+  light?
+  (bool enabled light-enabled?)
+  (int type %light-type)
+  (float-vec3 position light-position set-light-position!)
+  (float-vec3 direction light-direction set-light-direction!)
+  (float-vec4 color light-color set-light-color!)
+  (float cut-off light-cut-off set-light-cut-off!))
+
+(define %disabled-light (make-light #:enabled #f))
+
+(define (light-type light)
+  (let ((t (light-type light)))
+    (cond
+     ((= t 0) 'point)
+     ((= t 1) 'directional)
+     ((= t 2) 'spot))))
+
+(define (point-light? light)
+  (eq? (light-type light) 'point))
+
+(define (directional-light? light)
+  (eq? (light-type light) 'directional))
+
+(define (spot-light? light)
+  (eq? (light-type light) 'spot))
+
+(define* (make-point-light #:key (position (vec3 0.0 0.0 0.0))
+                           (color black))
+  (make-light #:enabled #t
+              #:type 0
+              #:position position
+              #:color color))
+
+(define* (make-directional-light #:key (direction (vec3 0.0 -1.0 0.0))
+                                 (color black))
+  (make-light #:enabled #t
+              #:type 1
+              #:direction direction
+              #:color color))
+
+(define* (make-spot-light #:key (position (vec3 0.0 0.0 0.0))
+                          (direction (vec3 0.0 0.0 -1.0))
+                          (color black)
+                          (cut-off (/ pi 4.0)))
+  (make-light #:enabled #t
+              #:type 2
+              #:position position
+              #:direction direction
+              #:color color
+              #:cut-off (cos cut-off)))
-- 
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