Mesh Preview Support (#26)

* Added OpenTK preview

* Bug fix

* Cleanup

* Initial Mesh preview support

* Mesh preview support

* Mesh preview - lighting and color

Unity Studio/fs.glsl

@@ -0,0 +1,27 @@
+#version 140
+
+in vec3 surfaceNormal;
+in vec3 toLightVector;
+in vec4 color;
+
+out vec4 outputColor;
+
+void main()
+{
+	vec3 lightColor = vec3(0.5, 0.5, 0.5);
+
+	// Ambient
+	float ambientStrength = 0.9;
+	vec3 ambient = ambientStrength * lightColor;
+
+	// Diffuse
+	vec3 unitNormal = normalize(surfaceNormal);
+	vec3 unitLightVector = normalize(toLightVector);
+	float nDotProduct = dot(unitNormal, unitLightVector);
+	float brightness = clamp(nDotProduct, 0, 1);  // max(nDotProduct, 0.0);
+	vec3 diffuse = brightness * lightColor;
+
+	// Output Color
+	vec4 result = color * vec4((ambient + diffuse/2), 0.0);
+	outputColor = result;
+}