Surface normals..

[james.lynch]

Hi All.
<?:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" />I came across some info which I thought may be benificial to anybody who surfaces quite a bit so I thiough I'd post it here.. below is the original question and followingis the responce I got from PTC.
Cheers,
James
Original Question..
I have a few questions about surface normals and the effect that they can have.
Firstly, What defines the normal direction of a surface (swept, extruded and blended if possible)? E.g. what defines the initial direction of a surface offset

 

[james.lynch]

Here is the responce from Tim and Paul at PTC.
James,<?:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" />
In answer to your question there are a number of elements which define a surface normal.
For example when sketching a line the normal is taken from the direction ofthe line creation (i.e left to right or right to left.) In the case of anarc the direction is taken counter clockwise.
The normal is to the left of the curve direction.
There are further elements which can overwrite these such as an extrude where the surface normals will be defined from the direction.
You are correct the initial direction of an offset is defined by its surface normal.
The normals for a boundary blend are taken from the first curve used to define the blend. Therefore you could change the curve order and this could change the surface normal.
You are correct about the surface merge. The normal for the quilt is taken from the primary surface.
Hopefully this will give you some answers to your questions
Regards
Paul.
____________________________________________________________ ___
I've attached a part to demo what I've been talking about
Cheers,
James
2007-03-07_143544_surf_normal_test.prt.zip

 

[james.lynch]

If anybody has any more information or experiencein dealing withthis I'd love to hear about it!


Cheers,


James

 

[design-engine]

You are trying to get a surface to sweep relative to the
pull direction. (needed if you are using a sweep instead of draft)



SURFACE NORMAL: A surface normal is a line perpendicular to a line (at a point) that is tangent to a curve
or surface at a point. Basicly a take on the first theorem of Calculus.





Oh.. I forgot to say hi James. We got 60 degree weather in Chicago today. Bet is is raining in england.




Edited by: design-engine

 

[james.lynch]

Hi Bart, well yes it is raining! (in Ireland I might add

) and I have a cold and I feel miserable!

but hey, colds pass, you come to enjoy the rain and I'm still left in this beautiful country sourounded by Guinness!

Happy almost Paddys Day!


I think what yo've described is surface normal at a point - lime a porqupine analysis of a surface, however, ProE also has it's own definition of a surface normal - and it's very dependant on quite a few things (dependong on how your surface was created! which I found a little confusing!


Anyway - though the info may be of use to somebody!


Good talking to you again Bart!


Cheers,


James


p.s. how's everything at Design Engine? see you at User this year?

 

[Jacoolo]

hi all

well I wont add anything more above, but I met situation that have with normals a lot to do. So what happened?

First I wanted achieve a shape as You can see below, and finally I did it, but first step by step:

View attachment 3251

but it was not so easy for me

first this is solid made by Edit>Thickness because all before is made in surfacing

so I prepare a surface and then drafted it as in pic below

View attachment 3252
and then I tried to made Edit > Thickness but without result

View attachment 3253

so it came to me that those drafts surface are cause of problems, but why - answer : strange result in normal offset

so I redifined the sketch and converted it to spline as below by Edit > conver to > Spline

View attachment 3254

so finally my draft was looking like that

View attachment 3255

and that was it - no problem with Edit>thickness

thank You for attention))