Why do all solid modelers use sketch planes

[10931418]

Serious question. I have used crio, Pro-E, i am a cswp in solidworks, i have used inventor and fusion. Why do all of these softwares use the sketch plane method? 

Then, if you compare to other 3d software like maya, blender, sketchup, 3dsmax, they do not use it? 

this is NOT a thread saying the other software is better. Im strictly wanting to know why the aforementioned use sketch planes? why is it part of the software? why did the devs choose that type of drawing process?

thansk a million

[dsouzasujay]

Hi @10931418 

A CAD software uses basic Cartesian coordinate system(XYZ).

In 2D, you specify points/curves on the XY plane, also called the work plane. The work plane is similar to a flat sheet of grid paper
For 3D modelling we include Z-axis. By adding the Z-axis, a 2D object becomes 3D.

[10931418]

correct:) but sketchup is all 3d space with x,y,z and yet no sketch planes. 

[莫凡法]

This is the difference between Engineering CAD software and Art CAD software.
The purpose is not the same and the design method is not the same.
If you compare some tutorial for Blender or Fusion, it is clear. I don't say that you can make a Engineer part in a Art software but it is not very convenient.

[TrippyLighting]

Very interesting question!

@dsouzasujay most CAD software also allows you to model with geometric primitives and no sketches are needed. I use ZW3D for some projects. The primitives in ZW3D are fully parametric and not based on sketches. But it also has Sketches 😉 

@莫凡法 not sure the distinction you made between Engineering CAD and Art CAD can explain the reason for the need for Sketches. In Autodesk Alias you don't work with sketches and IIRC neither do you in Altair Inspire Studio.

[10931418]

correct, i understand the differences between the 2 sinec i use sketchup pro for 5 years and i am also a certified solidworks user with my CSWP

i just want to know why all the above modelers use sketch planes? in sketchup pro, i can make parts to the nearst 0.0001mm with no issues. I can constrain all my parts as well. 

however, i want to know why all the top modeling software devs picked a sketch plane system:)

[TrippyLighting]

@10931418 try to model in a parametric 3D CAD software without a Sketch.

Obviously you'd have to use something else than SolidWorks, or Fusion 360.

While I think the purpose of a Sketch will become evident quickly when you do that, that will not tell the whole story.

I am old enough to have started mechanical designs on pencil/paper and ink/transparency. Most if not all manufacturing drawings were 2D only and did not include a 3 dimensional view of the object(s) in the drawing.

You had to derive the third dimension from the three main views.

When CAD software and particularly parametric solid modelers were developed, the purpose was to speed up the drafting and design and drafting efforts and to make changes easier and associative. Most manufactured stuff was  prismatic and more 2.5 D than real 3D and the geometry was derived from a single outline.

It was much easier to sketch the outline and do one extrude and be done, instead of combing a number of primitive shapes with Booleans  (GSG).

Even software that does offer wireframe geometry where curves/lines/arcs don't have to be captured in the container of a sketch, often offer sketches.

A Sketch serves as a container to hold all the constraints and dimensions, construction geometry etc. that make a sketch parametric.

The keyword here is parametric.

Some of the mesh/polygon modelers you named  use a different paradigm for parametric modeling called a modifier stack or offer fully procedural modeling. This is not sketch based and has a different purpose.

[10931418]

ok, so its the fact that all the modelers that use sketch planes are parametric modelers? I think i see where you are going with this.

Sketchup pro, even though i can make parts that are very precise and accurate not using a sketch plane system, they are NOT parametric in anyway.

so using a sketch plane to make a 2d sketch holds all the data for it to be parametric? 

Im guessing free sketching like sketchup would be very difficult to make parametric because if you just change the length of one line, and all the lines and faces touch, its not sure how to update the rest of the model accordingly?

thanks for that answer

PS, anyway to change the "10931418" as my screen name to something else? that is my schools way of registering with autodesk is a number

[CGBenner]

@10931418 

To change your forums name, try the tips in THIS POST.