Hey. I've been enjoying OpenTK now for a while but was code generating my own models(simple stuff, spheres and boxes...). I decided to use Collada files but XSD kept erring on the schema, and then after modifying the schema to work it seemed pretty unclear with conversions and stuff. So, i went through the whole Collada 1.5 spec and tried to class the entire thing. below is my Sourceforge link that contains the files. Keep in mind it has no direct connection to OpenTK, its just a set of classes to represent hopefully the entire Collada spec so you can use Collada models in your own rendering setup.