render: Add framebuffers.

4 files changed, 152 insertions, 10 deletions

diff --git a/Makefile.am b/Makefile.am
index fa84dd6..c9a563e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -54,6 +54,7 @@ SOURCES = 					\
   chickadee/render/shader.scm			\
   chickadee/render/vertex-buffer.scm		\
   chickadee/render/viewport.scm			\
+  chickadee/render/framebuffer.scm		\
   chickadee/render/shapes.scm			\
   chickadee/render/sprite.scm			\
   chickadee/render.scm				\
diff --git a/chickadee/render.scm b/chickadee/render.scm
index efb5004..9588a95 100644
--- a/chickadee/render.scm
+++ b/chickadee/render.scm
@@ -26,16 +26,19 @@
   #:use-module (chickadee math matrix)
   #:use-module (chickadee render gpu)
   #:use-module (chickadee render blend)
+  #:use-module (chickadee render framebuffer)
   #:use-module (chickadee render shader)
   #:use-module (chickadee render texture)
   #:use-module (chickadee render vertex-buffer)
   #:use-module (chickadee render viewport)
   #:export (current-viewport
+            current-framebuffer
             current-blend-mode
             current-depth-test
             current-texture
             current-projection
             with-viewport
+            with-framebuffer
             with-blend-mode
             with-depth-test
             with-texture
@@ -44,6 +47,7 @@
             gpu-apply*))
 
 (define *current-viewport* null-viewport)
+(define *current-framebuffer* null-framebuffer)
 (define *current-blend-mode* 'replace)
 (define *current-depth-test* #f)
 (define *current-texture* null-texture)
@@ -52,6 +56,9 @@
 (define (current-viewport)
   *current-viewport*)
 
+(define (current-framebuffer)
+  *current-framebuffer*)
+
 (define (current-blend-mode)
   *current-blend-mode*)
 
@@ -74,6 +81,9 @@
 (define-syntax-rule (with-viewport viewport body ...)
   (with (*current-viewport* viewport) body ...))
 
+(define-syntax-rule (with-framebuffer framebuffer body ...)
+  (with (*current-framebuffer* framebuffer) body ...))
+
 (define-syntax-rule (with-blend-mode blend-mode body ...)
   (with (*current-blend-mode* blend-mode) body ...))
 
@@ -133,6 +143,10 @@
 
 (define-syntax-rule (gpu-apply* shader vertex-array count . uniforms)
   (begin
+    ;; It's important that the framebuffer is set before setting the
+    ;; viewport because applying a new viewport will clear the current
+    ;; framebuffer.
+    (gpu-state-set! *framebuffer-state* (current-framebuffer))
     (gpu-state-set! *viewport-state* (current-viewport))
     (gpu-state-set! *blend-mode-state* (current-blend-mode))
     (gpu-state-set! *depth-test-state* (current-depth-test))
diff --git a/chickadee/render/framebuffer.scm b/chickadee/render/framebuffer.scm
new file mode 100644
index 0000000..39e4bfa
--- /dev/null
+++ b/chickadee/render/framebuffer.scm
@@ -0,0 +1,125 @@
+;;; Chickadee Game Toolkit
+;;; Copyright © 2017 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:
+;;
+;; Render to texture.
+;;
+;;; Code:
+
+(define-module (chickadee render framebuffer)
+  #:use-module (oop goops)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-9)
+  #:use-module (system foreign)
+  #:use-module (gl)
+  #:use-module (gl enums)
+  #:use-module (chickadee render gl)
+  #:use-module (chickadee render gpu)
+  #:use-module ((chickadee render texture) #:select (make-texture null-texture))
+  #:export (make-framebuffer
+            framebuffer?
+            framebuffer-texture
+            null-framebuffer
+            apply-framebuffer
+            *framebuffer-state*))
+
+(define (generate-framebuffer)
+  "Generate a new OpenGL framebuffer object."
+  (let ((bv (u32vector 1)))
+    (gl-gen-framebuffers 1 (bytevector->pointer bv))
+    (u32vector-ref bv 0)))
+
+(define (generate-renderbuffer)
+  "Generate a new OpenGL renderbuffer object."
+  (let ((bv (u32vector 1)))
+    (gl-gen-renderbuffers 1 (bytevector->pointer bv))
+    (u32vector-ref bv 0)))
+
+(define-record-type <framebuffer>
+  (%make-framebuffer id renderbuffer-id texture)
+  framebuffer?
+  (id framebuffer-id)
+  (renderbuffer-id framebuffer-renderbuffer-id)
+  (texture framebuffer-texture))
+
+(define null-framebuffer
+  (%make-framebuffer 0 0 null-texture))
+
+(define <<framebuffer>> (class-of null-framebuffer))
+
+(define (free-framebuffer framebuffer)
+  (gl-delete-renderbuffers 1
+                           (bytevector->pointer
+                            (u32vector
+                             (framebuffer-renderbuffer-id framebuffer))))
+  (gl-delete-framebuffers 1
+                          (bytevector->pointer
+                            (u32vector
+                             (framebuffer-id framebuffer)))))
+
+(define-method (gpu-finalize (framebuffer <<framebuffer>>))
+  (free-framebuffer framebuffer))
+
+(define (apply-framebuffer framebuffer)
+  (gl-bind-framebuffer (version-3-0 framebuffer)
+                       (framebuffer-id framebuffer)))
+
+(define *framebuffer-state*
+  (make-gpu-state apply-framebuffer null-framebuffer))
+
+(define make-framebuffer
+  (let ((draw-buffers (u32vector (version-3-0 color-attachment0))))
+    (lambda* (width height #:key (min-filter 'linear) (mag-filter 'linear)
+                    (wrap-s 'repeat) (wrap-t 'repeat))
+      "Create a new framebuffer that renders to a texture with
+dimensions WIDTH x HEIGHT."
+      (let* ((framebuffer-id (generate-framebuffer))
+             (renderbuffer-id (generate-renderbuffer))
+             (texture (make-texture #f width height
+                                    #:min-filter min-filter
+                                    #:mag-filter mag-filter
+                                    #:wrap-s wrap-s
+                                    #:wrap-t wrap-t))
+             (framebuffer (%make-framebuffer framebuffer-id
+                                             renderbuffer-id
+                                             texture)))
+        (gpu-state-set! *framebuffer-state* framebuffer)
+        ;; Setup depth buffer.
+        (gl-bind-renderbuffer (version-3-0 renderbuffer)
+                              renderbuffer-id)
+        (gl-renderbuffer-storage (version-3-0 renderbuffer)
+                                 (pixel-format depth-component)
+                                 width
+                                 height)
+        (gl-framebuffer-renderbuffer (version-3-0 framebuffer)
+                                     (arb-framebuffer-object depth-attachment)
+                                     (version-3-0 renderbuffer)
+                                     renderbuffer-id)
+        ;; Setup framebuffer.
+        (gl-framebuffer-texture-2d (version-3-0 framebuffer)
+                                   (version-3-0 color-attachment0)
+                                   (texture-target texture-2d)
+                                   ((@@ (chickadee render texture) texture-id)
+                                    texture)
+                                   0)
+        (gl-draw-buffers 1 (bytevector->pointer draw-buffers))
+        ;; Check for errors.
+        (unless (= (gl-check-framebuffer-status (version-3-0 framebuffer))
+                   (version-3-0 framebuffer-complete))
+          (error "Framebuffer cannot be created"))
+        framebuffer))))
diff --git a/chickadee/render/gl.scm b/chickadee/render/gl.scm
index 005194b..bbe3c44 100644
--- a/chickadee/render/gl.scm
+++ b/chickadee/render/gl.scm
@@ -220,16 +220,18 @@ object.")
                                                 -> void)
   "Attach a renderbuffer object to a framebuffer object.")
 
-(export glGenFramebuffers
-        glDeleteFramebuffers
-        glBindFramebuffer
-        glFramebufferTexture2D
-        glCheckFramebufferStatus
-        glGenRenderbuffers
-        glDeleteRenderbuffers
-        glBindRenderbuffer
-        glRenderbufferStorage
-        glFramebufferRenderbuffer)
+(export (glGenFramebuffers . gl-gen-framebuffers)
+        (glDeleteFramebuffers . gl-delete-framebuffers)
+        (glBindFramebuffer . gl-bind-framebuffer)
+        (glFramebufferTexture2D . gl-framebuffer-texture-2d)
+        (glCheckFramebufferStatus . gl-check-framebuffer-status)
+        (glGenRenderbuffers . gl-gen-renderbuffers)
+        (glDeleteRenderbuffers . gl-delete-renderbuffers)
+        (glBindRenderbuffer . gl-bind-renderbuffer)
+        (glRenderbufferStorage . gl-renderbuffer-storage)
+        (glFramebufferRenderbuffer . gl-framebuffer-renderbuffer))
+
+(re-export (%glDrawBuffers . gl-draw-buffers))
 
 
 ;;;