From a8a9c3962e78e01ca04e8f67115c15ea0a74592f Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 25 Oct 2018 08:46:25 -0400
Subject: render: buffer: Add render-vertices/instanced procedure.

* chickadee/render/buffer.scm (render-vertices/instanced): New procedure.
---
 chickadee/render/buffer.scm | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/chickadee/render/buffer.scm b/chickadee/render/buffer.scm
index 83a2925..5d13c2e 100644
--- a/chickadee/render/buffer.scm
+++ b/chickadee/render/buffer.scm
@@ -77,7 +77,8 @@
             vertex-array-mode
             null-vertex-array
             *vertex-array-state*
-            render-vertices))
+            render-vertices
+            render-vertices/instanced))
 
 ;;;
 ;;; Buffers
@@ -529,3 +530,13 @@ which attributes advance when rendering multiple instances."
                           (typed-buffer-length indices))
                       (typed-buffer-type-gl indices)
                       %null-pointer)))
+
+(define* (render-vertices/instanced array instances #:optional count)
+  (gpu-state-set! *vertex-array-state* array)
+  (let ((indices (vertex-array-indices array)))
+    (gl-draw-elements-instanced (vertex-array-mode-gl array)
+                                (or count
+                                    (typed-buffer-length indices))
+                                (typed-buffer-type-gl indices)
+                                %null-pointer
+                                instances)))
-- 
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