Beginning of parametric (python) templates in the Drawing Module

It's been a passing since the last entry. Unfortunately I've run out of beer and the fridge is empty, so tea again will suffice for a quite casual evening in programming.

After some discussion on the forums, I think I eventually persuaded everyone that SVG templates are simply not right for the job. Admittedly it's a nice standard and is great for customisation and has worked very well in the previous version available in FreeCAD. It also allows easy customisation and post-editing with other graphical editors such as Inkscape.  In fairness, Inkscape was not built for this job, even if there are several attempts at adding CAD functionality into the mix.

The problems using SVG for templates as I see it:

As far as I'm aware it's not adopted by any Mechanical CAD Package. I won't get into the discussion, but the biggest problem with using this template format is that there is no easy way to translate this into other formats such as .dxf, .dwg (Autocad / Teigha) or even our own representation if we ever needed it.

Dealing with XML is not impossible, and can be quite easy to manipulate using DOM (Document Object Model) functionality built into Qt. However, interacting with it through QGraphicsView is not great even if we have QSvg - which is apparently now obsolete. The other original idea was to parse any text fields and turn these into editable text boxes, but this alone creates further impracticalities.

The other big problem that seemed to be happening was the size and variation between templates based primarily on the paper size and the standard used (ANSI, ISO, Arch). There is nothing stopping someone creating these but in the future if these maintained it creates a lot of duplication of work.

I decided that we might as well do it RFT (right first time) rather than wait after the maiden release of the new module, which could be later in the year now.

Parametric driven templates

The combination of having endless combinations of templates was impractical. Some professional Mechanical CAD systems actually have limited number templates available. Instead, there was an attempt to to generate the SVG template using a python script. In the end. the best solution is to use a customisable python script to automatically generate the geometry, text fields and other extras for the template.

This script runs each time page dimensions change and is passed important properties such as page type, width, height, fields required and can create the frame, title blocks and so on, to the user's liking. I'd envisage an interface panel for customising this.

Any template geometry, fields etc. are abstract entities and are stored within the document feature. This can be then easily processed by an export script to be usable in different file formats.

Having abstract types allows isolation of individual elements in a template much easier. Practically this means if a text field is created, a text editing place holder is created and can be more easily manipulated. The same will go for Template annotations which still need work.

The only problem with this method, is we are somewhat restricted to the drawing functions and data types implemented. This might be lines, rectangles, arcs, text. Some CAD programs allow their sketch functionality to be used on top of their drawings. In some cases it can be quite useful, however, considering the maturity of the module, I don't think is appropriate or demanded.

I'll shut up now and show a picture.

This is a square page with a isometric view on it. Those lines across the page were created using

App.ActiveDocument.Template.drawLine(x1,y1,x2,y2);
App.ActiveDocument.Template.touch()

I'm still not sure yet how to organise the script so it knows about Template. However, this is to just show it working. I'm looking for people who can parametrically create a nice python script for generating scripts - don't expect me touching python!

Dimension Placeholders:

Some people will like this. From a solidworks background you can use custom placeholders for dimensions/sketcher datums. It's quite neat and allows some customisation where you may need it. 

For now my implement uses placeholders where there is a content field and the placeholder %value is the datum size.

That's all for  now folks!

Creating FreeCAD Lux Render Template

This is for the upcoming Render Module. Despite my very limited experience with rendering and modelling it appears that to get that 'wow' factor it will take a lot of scenes. Most people have better things to do so that is where templates come into play.

This guide will hopefully show how it will be possible to specify your own templates (for lux render):

Beginning with Blender & Lux Render:

The easiest way to create a template is to start with blender. A useful build and instruction guide for compiling Lux Render and using this in  Blender has been provided by Yorik on his blog

I don't have any clue how to use Blender, so you will have to figure that for yourselves. Nevertheless the important that you must have the scene normalised to a unit length. Ideally you have a cube with side lengths as one and build up a scene around this.

This is important because the scene will be scaled to the bounding box of the scene. I cannot guarantee this will work in all situations but it should give satisfactory results. Within blender you will need to export the scene to a  Lux Render Scene File Format with an extension .lxs 

Yorik created three example scenes that I am going to show you how to import as a Render Template in FreeCAD, these I have made available using google docs

Importing templates into FreeCAD:

For the scene template, we only need to find lights, geometry and materials information.

Materials are most likely to be used on the geometry within the scene. Using a templates like this means we can texture surfaces, which isn't going to appear within FreeCAD in the near future.

In this example open up luxscene-classic.lxs

Essentially we need everything from World Begin to World End. So extract all of this and you should be left with http://pastebin.com/qe3m0qXu 

One thing we need to change:

I discovered the long way that there is a problem with the way Blender exports the scene information to Lux Render. Unfortunately, you will need to go through the file and look for lines like these:

Transform [-0.083770856261253 0.000000133886644 -0.996485054492950 0.000000000000000 -0.000000133886729 1.000000000000000 0.000000145614280 0.000000000000000 0.996485054492950 0.000000145614365 -0.083770856261253 0.000000000000000 -0.465571254491806 -0.011301971040666 0.364225387573242 1.000000000000000]

These are transformation Matrices. These need to be removed and replaced with seperate Translation and Rotation properties for each object like so:

Tanslate x y z

Rotate angle x y z

With the rotation, you specify an angle about a given axis, so in the case of blender this may have to be done three times, in the x,y,z directions.

For example in the classic scene:

Select the Plane.006 object and look the object properties

So you would replace the Transform line with this: 

Tanslate 0.459 -0.01 0.6

Rotate 253.4 0 1 0

Place this into a file such as luxsceneClassic.lxs

Then inside the FreeCAD build folder navigate to data/Mod/Raytracing/Templates

Create a folder in Templates/Lux to hold your template such as Templates/Lux/Classic. Then copy the file luxSceneClassic.lxs you previously created inside here.

Within the same folder create an xml file and copy into this file the following excerpt:

<?xml version="1.0" encoding="iso-8859-1" ?>

<!--

 FreeCAD Scene Template for LUX Render, see http://free-cad.sourceforge.net for more information...

-->

<Document SchemaVersion="1">

  <Templates render="lux">

    <Template id="lux_classic" source="external">

      <label>Lux Classic Scene</label>

      <description> Classical Elegance</description>

      <provides>classic</provides>

      <filename>luxSceneClassic.lxs</filename>

    </Template>

  </Templates>

</Document>

For reference you only have to change the following:

• id="lux_classic" : this attribute must be a unique identifier for the template
• <label> Label for the scene template </label> : a graphical name for the scene
• <description>Description for the scene template</description> : a descriptive identifier
• <filename>luxSceneClassic.lxs</filename> the file name that contains the scene information

You should have a file structure like this:

I am not sure when you compile and build FreeCAD each time if this template folder will be deleted. Most likely not. Later, I will make a preference option so you can use your own folder. 

Using the Template:

Launch FreeCAD and switch to the Raytracing Workbench:

Create a new Render Feature.

A task view will appear. FreeCAD will automatically find your template. You can now select the template that is used in your scene. If nothing appears when you render, it is likely that the Lux Render Scene File Format has incorrect syntax...

Now position the camera where you want and hit Preview Window. Currently there might be times where the render is just a black screen - so to quickly solve this just play around with the camera a bit. 

Hopefully this make sense, feel free to post questions on here if you're stuck!

We have working render templates!

After a few days of working with a day off finally getting out of the small village I live in, we have a render template system that is working.

Here is the Schenkel part - does anybody know what this is? Attached with a Matte material with an orange colour:

Before:

After the render:

Now lets turn it into glass!

Here I am using the classic theme created by Yorilk. It's a basic box scene with two area lights. It's not bad to say it takes about 30 seconds to set up.