How to convert STL
to Collada?

STL (STereoLithography) is a file format native to the stereolithography CAD software. This file format is supported by many other software packages; it is widely used for rapid prototyping, 3D printing and computer-aided manufacturing. STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact.

Collada (COLLAborative Design Activity) is an interchange format for interactive 3D applications. Originally developed by Sony Computer Industry, now it is managed by the Khronos Group, a member-funded industry consortium, which now shares the copyright with Sony, Recently Collada has been well adopted by ISO as a publicly available specification, ISO/PAS 17506.

It is an XML-based schema that allows data exchange among 3D Digital Content Creation tools, such as SketchUp, Maya, 3ds Max, and Rhino. COLLADA files have the *.dae file extension, which stands for digital asset exchange.