From 1425a0dc73f7fa37612b7a82f090e9b10ddebf25 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 1 Sep 2023 09:00:01 -0400
Subject: First pass of rendering engine rewrite.

The (chickadee graphics gpu) module now handles most of the low-level
OpenGL object creation/deletion/binding.  The (chickadee graphics
engine) module handles the with-graphics-state stuff via a render
context object.  There's lots of stuff that isn't great, but it's the
first step towards a graphics backend agnostic rendering layer.
---
 examples/triangle.scm | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 examples/triangle.scm

(limited to 'examples/triangle.scm')

diff --git a/examples/triangle.scm b/examples/triangle.scm
new file mode 100644
index 0000000..2debc85
--- /dev/null
+++ b/examples/triangle.scm
@@ -0,0 +1,84 @@
+(use-modules (chickadee)
+             (chickadee math vector)
+             (chickadee graphics buffer)
+             (chickadee graphics engine)
+             (chickadee graphics shader))
+
+(use-modules (gl enums))
+
+(define vertex-array #f)
+(define shader #f)
+
+(define (load)
+  (define verts
+    (make-buffer #f32(0.0 0.0
+                          640.0 0.0
+                          320.0 480.0)))
+  (define colors
+    (make-buffer #f32(1.0 0.0 0.0 1.0
+                          0.0 1.0 0.0 1.0
+                          0.0 0.0 1.0 1.0)))
+  ;; This isn't necessary for a single triangle, but we're doing it
+  ;; anyway just to exercise that code.
+  (define indices (make-buffer #u32(0 1 2) #:target 'index))
+  (set! vertex-array
+        (make-vertex-array
+         #:indices (make-vertex-attribute
+                    #:buffer indices
+                    #:type 'scalar
+                    #:component-type 'unsigned-int)
+         #:attributes `((0 . ,(make-vertex-attribute
+                               #:buffer verts
+                               #:type 'vec2
+                               #:component-type 'float))
+                        (1 . ,(make-vertex-attribute
+                               #:buffer colors
+                               #:type 'color
+                               #:component-type 'float)))))
+  (set! shader (strings->shader
+                "
+#ifdef GLSL330
+layout (location = 0) in vec2 position;
+layout (location = 1) in vec4 color;
+#elif defined(GLSL130)
+in vec2 position;
+in vec4 color;
+#elif defined(GLSL120)
+attribute vec2 position;
+attribute vec4 color;
+#endif
+#ifdef GLSL120
+varying vec4 fragColor;
+#else
+out vec4 fragColor;
+#endif
+uniform mat4 mvp;
+
+void main(void) {
+    fragColor = color;
+    gl_Position = mvp * vec4(position, 0.0, 1.0);
+}
+"
+                "
+#ifdef GLSL120
+varying vec4 fragColor;
+#else
+in vec4 fragColor;
+ #endif
+#ifdef GLSL330
+out vec4 outFragColor;
+#endif
+
+void main (void) {
+#ifdef GLSL330
+    outFragColor = fragColor;
+#else
+    gl_FragColor = fragColor;
+#endif
+}
+")))
+
+(define (draw alpha)
+  (shader-apply shader vertex-array #:mvp (current-projection)))
+
+(run-game #:load load #:draw draw)
-- 
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