Possible problem in drawing. Missing lines

Discussions about the development of the TechDraw workbench
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dcapeletti
Posts: 383
Joined: Wed Jul 23, 2014 2:27 pm

Possible problem in drawing. Missing lines

Postby dcapeletti » Fri Jul 26, 2019 11:51 pm

Hello, I'm attaching the file so you can verify it.
I enclose an image where I mark the missing line.

If it's a design error, I'll be grateful for your recommendations. I hope you can help me.

Thanks

OS: Debian GNU/Linux 9 (stretch) (GNOME/default)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.17445 (Git) AppImage
Build type: Release
Branch: master
Hash: 741dddf25485f692596faa9b7911e2e0f5d362a3
Python version: 3.7.3
Qt version: 5.9.7
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: Spanish/Argentina (es_AR)
Attachments
Engranaje.FCStd
(538.57 KiB) Downloaded 4 times
TechDraw error.png
TechDraw error.png (102.89 KiB) Viewed 287 times
wandererfan
Posts: 2887
Joined: Tue Nov 06, 2012 5:42 pm

Re: Possible problem in drawing. Missing lines

Postby wandererfan » Sat Jul 27, 2019 12:44 pm

dcapeletti wrote:
Fri Jul 26, 2019 11:51 pm
I enclose an image where I mark the missing line.

If it's a design error, I'll be grateful for your recommendations. I hope you can help me.
I think it is an OCC error in either the HLR algorithms, the Projector algorithms or both.

In your file, you are using Coarse View for FrontBottomLeft and Detail. (Coarse View uses the polygon approximation version of the HLR with the orthogonal Projector.)

If I set CoarseView off for FrontBottomLeft, I get your missing line back (red arrow), but also get some hidden lines being visible (blue arrows). I also get an extra red line(?!). (Precise version of HLR with orthogonal Projector).
PreciseArtifacts.png
PreciseArtifacts.png (63.84 KiB) Viewed 264 times

I get the best results by setting CoarseView off, Perspective on, and focus length of 1000mm. This collection of options uses the precise HLR with the perspective Projector.
Engranaje_Perspective.png
Engranaje_Perspective.png (252.14 KiB) Viewed 264 times
Can't see any obvious design errors, but it is good practice to use the Body as the Source for TechDraw Views, rather than one of the feature history entries (Pocket001).
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dcapeletti
Posts: 383
Joined: Wed Jul 23, 2014 2:27 pm

Re: Possible problem in drawing. Missing lines

Postby dcapeletti » Mon Jul 29, 2019 11:20 pm

Can't see any obvious design errors, but it is good practice to use the Body as the Source for TechDraw Views, rather than one of the feature history entries (Pocket001).
Thank you for your help and advice.
I've done what you tell me, but I still get errors in the projection. I think techdraw should still get some improvements. Are they planned for version 0.19?

Greetings
wandererfan
Posts: 2887
Joined: Tue Nov 06, 2012 5:42 pm

Re: Possible problem in drawing. Missing lines

Postby wandererfan » Wed Jul 31, 2019 2:29 pm

dcapeletti wrote:
Mon Jul 29, 2019 11:20 pm
TD/OCC always struggle with invalid shapes.

The first feature (Pad) in your chain fails Part.checkGeometry. The InvoluteGear passes, but PartDesign Pad and Part Extrude both create shapes that fail.
engranaje_checkGeometry.png
engranaje_checkGeometry.png (175.85 KiB) Viewed 168 times
If I take a copy of InvoluteGear, convert it to a Sketch with Draft, then use Part.Extrude on the Sketch, I get a valid solid that passes CheckGeometry and draws nicely in TD.
Engranaje_PadFromSketch.png
Engranaje_PadFromSketch.png (29.32 KiB) Viewed 168 times
I don't know why the original is invalid, but the manipulated version is good. Maybe there is a Sketcher/Part Design expert that can explain.
Attachments
Engranaje_PadFromSketch.FCStd
(743.77 KiB) Downloaded 3 times
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