Users may apply an AssetShader to the entirety of the room's contents, portals and users' avatars through the attributes below. This global shader may be overwritten on a per-Object basis by setting the shader_id attribute for each Object. At the moment only JanusVR native supports glsl shaders.
http://janusvr.com/docs/build/roomtag/index.html#Room
shader_id - (default "") The AssetShader id to use as the global shader.