My English is not good, sorry for that.
How to Convert some Models from Penumbra to Amnesia:
At first you must Creat a New Folder name the Model you will convert.
Example: Desk01
Then you copy all files with the name Desk01(.DAE .ENT .JPG .MAT .TGA)
Look @ Picture:
Then you open the MaterialEditor from Amnesia and open a .MAT file.
Try to search a file with similar config.
Example: i will convert a Desk so i open the .MAT file from workdesk of amnesia.
Look @ Picture:
then you change the texture file (in this example under diffuse and nmap)
with the files from Penumbra and save an overwrite the original Penumbra file in the folder you create in step one.
The last step, you open the Model Editor from Amnesia.
Then you open at first the .ENT file ( in example i open the desk01.ent)
then you insert a mesh(you found it under file) and insert the .DAE (in example i open the desk01.dae)
Look @ picture:
Ready.
It could be you must change some things. In example i must change the place from the drawer. And you must create a shape. For the configuration you can look at the existing files from Amnesia.
I hope its useful and your understand my broken english
if they are some problems, ask me. I try to help.