Autocad equivalent of a viewport

Hello everyone. Like anyone else coming from the autocad and/or revit world, I have a lot of doubts about certain basic stuff. I’ve made Robert Burke’s tutorial for the precise modeling and I’m really happy about the progress I’ve made(btw I have to thank him in the next few days). I know for sure that I cannot replace a CAD with Blender but there are some workflows that are valid even for the blender modeling style and I’d like to know how far can I get.

I’d like to know if having one only object I could imitate the viewport behavior of autocad(Several views from the same object). For example to get a right view and a top view on a layout without having to duplicate the object. This way, I don’t have to modify all the copies of the object if I have to make some minor changes in the geometry. This could also reduce the vertex’s total number.

BTW: This forum is a lot less scarier thatn those dedicated to CAD and programming. It’s nice to know that there are other people that can have fun modeling.

Thanks!

TheRainMaker

Hello
you can use Ctrl-Alt-Q shortcut to get a “Quad view” or read this about how to split windows:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Interface/Window_system/Arranging_frames
Bye

Blender is mainly a polygonal modeler and polygonal modeling is approximation, originally developed for on-screen purposes. The precision and detail we care about is relative for visual purposes, not absolute to fulfil engineering requirements. Polygonal modeling workflows don’t apply well when trying to achieve high precision (within acceptable tolerance) but you can do it to an extent, it’s just harder. You have started with a fine sport of fencing but switched your sword to a swordfish - sound similar but are very different.

These should help tackle many interface related questions and issues https://www.youtube.com/playlist?list=PL0AfIdK08E7_PKsXOO_yuAql9b3hdcwPR

Some way in Blender to deal with exact dimensions instead of approximation

In Blender it’s still possible to change the dimension of an existing edge to an exact precise one in edit mode.
By example you have an edge that is 52.5cm but you want to set it to 45cm.
http://i.imgur.com/sYBCWAC.jpg

Select that edge , press S then = (or numpad *) in order to enable the advanced numeric input method mode ( that is the normal one, as the default “simple” would make everything you type in a division to be 1/whatever instead of what you want http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.70/UI ) and type 45/52.5 then press ENTER , as a result :

http://i.imgur.com/yuGbq3H.jpg

As you see it’s really not something that user friendly or even obvious to do (as i guess not everyone know about that simple/advanced numeric input switch, i never heard about it until someone told me this was a new feature introduced back in 2.70) and probably why people have always problem when it comes to setup exact dimensions for their edges.

I have no idea if there’s an addon with a simple panel that would allow the user in edit mode to input the dimension change manually (while Blender does the scaling and the calculation internally) you would obtain a real user friendly method to make your modelling gaining precision very easily. But something that should be good to have anyways.

Thanks OTO and JA12 for your comments, I am slowly lerning the basics and it’s true that on youtube there are a lot of tutorials for blender.

I really appreciate the quick scale method that Sanctuary propose. In Autocad you can input also simple values by the means of a formula. This will help me in the inmediate future ;).

In Autocad a viewport is a window element. Consider it like a rectangle, but you can link the interior of it to a certain view and scale to avoid the dangers of reproducing objects before finishing the model. I am reading things about linking and proxy linking models to see if it can help me.

Just to clarify after that comment, my point wasn’t about approximate values but approximation of curves and surfaces which polygonal modeling is. There are no curves, just ones that are approximated with straight edges - More precision, more vertices and edges, more difficult to control and if you somehow manage, it’s still an approximation.


In 2D/3D CAD (NURBS or Solid Modeling) one could define a circle and the parameters could be a position and a radius (and height for a 3D cylinder). It gives a nice circle that has the same radius all around no matter which point is measured. The precision is given.

In polygonal modeling we add a circle, give it a position and a radius, and the number of vertices/sides. The result is an approximation of a circle which has that radius but only at the points where the vertices are. We could start with more vertices and get better approximation, but then we would also increase the complexity right from the start and have to control more geometry while modifying this shape.


Subdivision surface is a popular method to use a lot of geometry in a model while still maintaining controllable amount of control points. Most used subdivision algorithm across different packages is Catmull-Clark which Blender also uses, and it’s an approximation algorithm instead of interpolation. This gives nice looking curves but as precision goes, it’s even worse because it’s based on the control cage which is an approximation, and it then approximates that.

So the precision depends on the control cage and if we want less control points and use high subdivision level, it gives much smaller version of the original circle that had radius (or diameter) specified at the start. The subdivision doesn’t happen uniformly either, the diameter is not the same all around.

That’s still just a circle, not a complex 2D or 3D shape. And none of that usually matters since we don’t need absolute precision when creating polygonal models with polygonal modeling tools. The precision is relative, relative to: features on the object itself, other objects, distance to camera, scale, detail level, and even render resolution.

Common instruction is to “have the finalized model in real world size” but forget to mention that within 1-3% is good enough when selling models. 3D printing almost counts because curves and surfaces are defined only with real geometry and we need to think about printing tolerances, clearances for interlocking parts, etc. which is a pain in a backside. Luckily those tolerances and clearances are still quite loose, smallest being 0.1mm which in engineering is like waving a finger in a hangar.