view3dscene is a viewer for many 3D model formats: X3D, VRML, Collada, 3DS, MD3, Wavefront OBJ, STL and (2D) Spine JSON.
Complete documentation on https://castle-engine.io/view3dscene.php .
Using Castle Game Engine, see https://castle-engine.io/ .
tovrmlx3d is a simple command-line program to convert various 3D file formats to X3D and VRML, and to pretty-print X3D and VRML. Note that you can also use view3dscene for this task (view3dscene has menu items to do it interactively, and command-line options to do it in batch mode). But sometimes using "tovrmlx3d" may be useful as it has lighter requirements (not linked with any GUI libraries, which is useful on a server).
The documentation of command-line options to perform convertion is on https://castle-engine.io/view3dscene.php#section_converting .
GNU GPL >= 2.