cmpolis
Fails to detect binary format STL file
Go to http://www.eng.nus.edu.sg/LCEL/RP/u21/wwwroot/stl_library.htm#Download and download the porsche STL file. The STL file is in binary format but the converter thinks it's ascii and so fails to convert it.
I have used that porsche file for other purposes, and believe there is some bad data in it.
Opening and saving the file as UTF-8, allows convetSTL to recoginze it as binary. I had another version of the file that I had "resized" through SOLIDWORKS, and that one converted just fine.
I believe the "blame" lies with the porsche file. Let me know if you actually need the porsche in ascii format, and I can get it to you.
Zeroing out the 80 byte header caused convertSTL to recognize it as a binary file. But that shouldn't be necessary. If the header doesn't start with ascii "solid" (optionally prefixed by spaces) then the file should be treated as a binary format file.
The format of the binary file seems fine. It has the correct number of bytes based on the number of facets. There is nothing in the file that should make convertSTL think it is an ascii formatted STL file.
Currently the script checks if the header has "solid" in it, and if it doesn't, it treats the file as a binary file. I was curious how/why it would think the porsche file was ascii, so I examined the file directly, and the first line DOES have "solid" in it!
File.new('porsche.stl', 'r').gets
#=> "104-9.stl tol 0.01 ac 0.02 solid layer 209 3DV*\x904O\u0002\u0000\xD7\xFD\u0018\xBD\u0000\u0000\u0000\...
Same thing for the brain-gear.stl
File.new('brain-gear.stl', 'r').gets
#=> "solid brain_gear\u0000STL Output \x8A#\u0001\u0000\u0000\u0000\u0000\u0000\u0000\u0000
So I'm thinking simply checking for "solid" is not a reliable way to detect binary vs ascii.
Ah, that explains what's happening. You could skip any leading spaces and then see if the next word is "solid".
OK, so this is interesting. A number of other tools/technics fail to detect these as binary files because the first "line" has non-binary data.
http://stackoverflow.com/questions/2355866/ruby-how-to-determine-if-file-being-read-is-binary-or-text https://github.com/djberg96/ptools
require 'ptools'
File.binary?('porsche.stl') #=> false
File.binary?('brain-gear.stl') #=> false
https://github.com/djberg96/ptools/blob/master/lib/ptools.rb#L90
def self.binary?(file)
return false if image?(file)
bytes = File.stat(file).blksize
bytes = 4096 if bytes > 4096
s = (File.read(file, bytes) || "")
s = s.encode('US-ASCII', :undef => :replace).split(//)
((s.size - s.grep(" ".."~").size) / s.size.to_f) > 0.30
end
https://github.com/brianmario/charlock_holmes
require 'charlock_holmes'
CharlockHolmes::EncodingDetector.detect('porsche.stl')
#=> {:type=>:text, :encoding=>"ISO-8859-1", :ruby_encoding=>"ISO-8859-1", :confidence=>75, :language=>"en"}
CharlockHolmes::EncodingDetector.detect('brain-gear.stl')
#=> {:type=>:text, :encoding=>"ISO-8859-1", :ruby_encoding=>"ISO-8859-1", :confidence=>60, :language=>"da"}
Using the unix file command does detect the file correctly.
file porsche.stl
#=> porsche.stl: data
file brain-gear.stl
#=> brain-gear.stl: data
file cylinder.stl
#=> cylinder.stl: ASCII text
And this works as well: https://www.ruby-forum.com/topic/122170#544577
class File
def self.binary?(name)
ascii = control = binary = 0
File.open(name, "rb") {|io| io.read(1024)}.each_byte do |bt|
case bt
when 0...32
control += 1
when 32...128
ascii += 1
else
binary += 1
end
end
control.to_f / ascii > 0.1 || binary.to_f / ascii > 0.05
end
end
File.binary?('porsche.stl') #=> true
Given what we've found I think we can come up with a reliable solution, but I need to set this aside for now.
Hi, I had same problem, it does not recognize binary stl file.
A binary stl file is defined as follow : BINARY STL file format is accessed by byte. The format is as follows: the first 80 bytes are used for description, and the next 4 bytes represents the total number of the facets(Long Int), followed by the facet information (normal and 3 vertices), the normal and vertices are stored in floating point format, each occupying 4 bytes. At the end of each facet information section, there are two bytes spaces, then the next facet is repeated till the end of the file. When BINARY format is used to describe STL file, the data size is much smaller than ASCII format, so most STL files available now use BINARY format.
<BINARY STL file format>::=<STL file entity name><facet number N>
@cmpolis I've got an AutoCAD-generated binary STL which is recognized as ASCII STL by the script,because it started by AutoCAD solid (containing solid).
I think https://github.com/cmpolis/convertSTL/blob/572a5e1ee1d7f4d370b2b4e5d32ba6517c11fa41/convertSTL.rb#L38 should be changed to the following:
if tempLine.start_with? "solid"
based on the documentations on wikipedia
A binary STL file has an 80-character header (which is generally ignored, but should never begin with "solid" because that may lead some software to assume that this is an ASCII STL file). and the aforementioned AutoCAD-generated file.
