1 files changed, 57 insertions, 0 deletions
diff --git a/data/simple.frag b/data/simple.frag
new file mode 100644
index 0000000..89480f7
--- /dev/null
+++ b/data/simple.frag
@@ -0,0 +1,57 @@
+#version 130
+#extension GL_ARB_explicit_attrib_location: require
+
+#define DO_LIGHTING 0
+
+/* Debug mode.  This will cause the value supplied as 'normal_cs' to be
+ * written as the output color.  The normal will be remapped from the usual
+ * [-1,1] range to [0,1].
+ */
+#define SHOW_NORMALS 0
+
+/* Approximate (u,v) at the current fragment.  Passed from the vertex shader,
+ * this is used to determine the base color of the fragment.
+ */
+in vec2 frag_uv;
+
+// Direction of the normal in camera-space.
+in vec3 normal_cs;
+
+// Direction to the light in camera-space.
+uniform vec3 light_dir_cs = normalize(vec3(0., 1., 0.));
+
+layout(location = 0) out vec4 color;
+
+void main(void)
+{
+	/* Partition the surface into a checkerboard of 10x10 tiles that
+	 * alternate colors.
+	 */
+	ivec2 tile = ivec2(floor(frag_uv * 10.));
+
+	vec3 base_color = bool((tile.x ^ tile.y) & 1)
+		? vec3(0.00784313679, 0.470588207, 0.996078372)
+		: vec3(0.00784313679, 0.992156804, 0.00784313679);
+
+	/* Renormalize the normal to account for interpolation errors.
+	 */
+	vec3 n_cs = normalize(normal_cs);
+
+	/* If the polygon is back-facing, change the color and invert the
+	 * normal.  This causes back-facing polygons to have different colors
+	 * and be correctly lit.
+	 */
+	if (! gl_FrontFacing) {
+		n_cs = -n_cs;
+		base_color = base_color.zxy;
+	}
+
+#if DO_LIGHTING
+	float diff = min(max(.2, dot(n_cs, light_dir_cs)), 1.);
+	color = vec4(base_color * diff, 1.);
+#elif SHOW_NORMALS
+	color = vec4(normal_cs * .5 + .5, 1.);
+#else
+	color = vec4(base_color, 1.);
+#endif
+}