COLLADA 3D models

COLLADA is the Khronos Group's open XML format for exchanging 3D models. SketchUp, Blender, 3ds Max, Maya, Esko's Studio and Cape Pack, and many other programs read and write it. A .dae file is the COLLADA document itself (its textures are usually image files beside it); a .zae is a zip that holds the document, a manifest.xml naming it, and its textures, so one file carries everything. ParametrIQ CAD reads COLLADA models to show with a folded drawing, and writes a 3D page as COLLADA.

Import

3D › Models and Products › Import Model… reads a .dae or .zae file and shows it with the folded drawing, as it does a glTF, OBJ, STL, PRC or U3D model (see 3D pages). The dialog also takes a web address of a .dae or .zae, and the model can be embedded in the drawing or linked to its file or address, as for other models (see Linked files and web addresses). What is read:

Units and up. The file's unit (its asset says how many metres one is: 0.0254 for inches, 1 for metres) and its up axis (X, Y or Z) are turned into millimetres with Z up, so the model stands up the right way at its real size. A file that doesn't say is taken as metres with Y up, as COLLADA says.
The scene. The meshes the scene shows, each where its nodes put it: nodes inside nodes, nodes used again from the file's library (a SketchUp component placed several times, say), and each node's matrices, moves, turns, scales and look-ats, in the order written. A file with no scene shows each of its meshes once, as modelled.
The meshes. Triangles, polygon lists, polygons, triangle fans and strips; each corner's position, normal and texture coordinates, however the file arranges them. Polygons are cut into triangles. Where the file gives no normals, each triangle's own are used.
The materials. Each material's colour (constant, Lambert, Phong or Blinn), how glossy it is, and how far it can be seen through; or the picture its colour comes from, as a texture. A material's parts are shown together.
Textures. Pictures (PNG, JPEG and the other common formats) are read from inside the .zae, beside the .dae (or the path it gives, or a file of that name beside it), or from inside the document itself (a data URI or hex data). Pictures over 2048 pixels across are scaled down.
Skinned and morphed models are shown as they were bound, not posed or animated.

Left out, and said in the message after the import: lines and points, the holes of polygons that have them (filled), skew transforms, meshes in other files, splines and solids that aren't meshes, pictures that can't be found or read (the part is shown without its texture), and anything else that can't be read, which is skipped rather than refusing the file. Cameras, lights and animations aren't read. A file that isn't COLLADA (or a .zae holding no COLLADA document) is refused with a message saying so. Files over 512 MB, pictures over 64 MB and models over ten million triangles aren't read in full.

When a model is embedded in the drawing, a .zae is kept as it is; a .dae (whose textures are in other files) is kept as one .glb, without its textures. To keep its textures with the drawing, link it, or zip it as a .zae.

Export

3D › Export › Export 3D Model…, choosing COLLADA (.dae) or COLLADA, zipped (.zae), writes the 3D page as it is shown (folded as far as it is now, with its model) as COLLADA 1.4.1, in millimetres with Z up, saying so: a part for each of the outside faces, inside faces and cut edges, and for each part of the model shown with it, each with its colour and opacity. A part with a texture (the model's own, say) has its texture coordinates too, its picture written as a PNG beside the .dae, or inside the .zae. File › Export › Export for Pallet Software › Export to Cape Pack… writes the folded case alone, for Cape Pack's shapes: see Cape Pack and TOPS Pro.

What ParametrIQ CAD writes as COLLADA reads back with 3D › Models and Products › Import Model… as it was.

About the format

COLLADA 1.4.1 and 1.5 are published by the Khronos Group and are free to read. A document's asset says its unit and up axis; its libraries hold the geometries (meshes), materials and effects (how a material looks), images, and nodes; and its visual scene places the geometries with a tree of nodes. COLLADA 1.5 describes the zipped .zae, with the manifest.xml whose dae_root names the document.