A few days ago I asked questions about the appearance of a DeltaCad drawing which I had sent to an HPGL plot file using the method posted by Bob (putting an HP5785A on a file redirection device ). I have investigated further using the HPGL information provided by Thibaud T-C and viewer advice from Steve Irick.
I have established that it is my plot file that is in error, not the resultant display produced the viewers I used - Q) The original diagram uses several line widths, the plot file lines all look the same. A) The HPGL file which I produced does not include any commands for setting the line width. HPGL can apparently do this through the PT command (Pen Thickness), but that does not appear in my output. There is also a SP command (Select Pen), which presumably would achieve the same effect if a real plotter has some thicker pens installed. At the start of my output SP1 is used, but the pen is not changed again until it is parked at the end of the job. In other words, the file does not try to use multiple line widths. Q) The original diagram has neatly aligned Times New Roman text, whereas in the HPGL plot it is not angled correctly and it is not Times New Roman. [The characters are positioned with their bottom left corners forming a sloping line as required, but each character is printed vertically. To get the correct layout, they should be rotated to be perpendicular to the slope] A1) The HPGL definition in PRINTGL does not explain how fonts are selected. There is a CS command (Character Set), but that only allows for selection of ASCII, ISO variant etc., not typeface. It seems as if there may be no way for a CAD program to control which typeface is used. A2) The corners of the characters are put on a sloping line because the plot data includes a set of positioning commands for each character. The software carefully works out a coordinate on a sloping line for each one. It then neglects to tell the ploter to rotate them to the intended angle. I was surprised when I saw what was happening - I expected there to be a command to postion the corner of a printed text string and one to rotate it, plus a single text string forming the entire label. Instead, it treats each character as a seperate entity. Now I have some new questions. I'm trying to understand whether it is DeltaCad that is imposing limitations, or is it that the 7585A can't handle all the commands available in HPGL so the spooler is purposely leaving them out - - Do other CAD programs give the same effect when writing to a 7585A? Has anybody tried it? You just need to draw a thick line and a thin line side by side, and some text on a slope, and then print the drawing to a 7585A redirected to a file. If you don't want to analyse your output file, send it to me and I'll go through it. - Could I use a different printer type with DeltaCad, and get better results - what is that better choice of printer? - Do HPGL or HPGL/2 in fact provide a way to control the typeface used (e.g. Times New Roman, Arial....)? If not, we're never going to be able to produce plotter files which match our drawings.... Many thanks, Steve L.
