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modeling approach

N

north3

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2008-01-24_051731_redo5.prt.zip
ive been struggling to model the area shown for some time now and wonder if anyone can suggest a more useable approach that would give a better result but still with nice smooth highlights. the section i have highlighted shouldnt really be round ,i think more parabolic but it when i change the shape it alters the highlights into something unacceptable...
 
I haven`t seen your model yet, but taking advantage of attached image I assume it can be done with VSS - the middle surface. Pick two trajectories - boundary edges from previous quilt. Set tangency for both trajectory and VSS should handle all smothly.
 
ive had a quick try of what you suggest but maybe because ive not used vss very much the results arent very good (bulging around the area im already having problems with)
also the rad at the end of the sweep (the small end) doesnt line up very well .....
 
I like how you layed out the model but sometimes less control is better with respect to hightlights. I teach to make the model as simple as possible and add complexity only in hindsite.

(i did not look at the model yet) But my first thought when coming into a turn is to let off the gas when those letting off the gas will crash. Maybe keeping it very simple is not the first thought but when managing light reflections simple is better.
 
hi bart
i tried to keep the number of sections as few as possible. if i omit what i think is the dodgey section the top shape dives away too quickly and i kind of like the top shape.maybe i should move that section to before where the curve starts going around the corner to help preserve the top shape ....?
 
I found you can often get the 2 dimensional shape (to satisfy the designers).... Se Pro/E uses 3 degree curves... ie. y=4x^3+2x^2+3x-2 If you try you can do a lot with the math of that 3 degree curve. In Alias Studio you might bump the curve up to a four or five degree curve and still get the plan view or the shape of the curve. The value here is you don't get the spans. Pro/E does not let us see isoparms *** yet **** and Pro/E will not let us force a 3 degree curve to the 4, 5, 6, or seven degree curve like in alias. *** yet *** I thought ten years ago we would have that power in Pro/E by now ... we do not. Well cars don't fly either.

What... in the case of Pro/E we don't see the spans. We see only tangency lines or lines that stem from where two curves join in the sketch. Minimize that will help as that complexity echoes thro-out the rest of the surface geometry.

If my students had to tease me by mimicking me they would say "simple is better" because when they have a strange reflection I minimize the underlying curve geometry and the reflection looks great. Do the opposite of what you think.... try it.




Edited by: design-engine
 
I do not how accurate design you want to achieve. I took a little attempt to follow your design. It appears it was easier while I do have two chamber pots for my kids at home. I took a look at their shape, and imho you overcomplicate your models. All details you put up front seems to be not neccessary.

ok to not only claim I prepare my model which is more simple them your one. It has not all details which real chamber pot contains. Howevever it is ver close to real part.



here is a model in WF 2.0



2008-01-25_034253_jerry.prt.rar
 
thanks i`ll look at how you approached doing it,though id like to try to keep faithful to what i have already drawn...
bart ...im not quite sure what you mean ...
 
well... I have a tutorial of a mouse i used to teach in a class. It was built with curves on a 2d plane and curves on an adjacent 2d plane. This will be difficult to explain....

three curves join to make one curve and maybe four curves join to make the other curve. All the curves come together to make a surface. notice the tangency lines that connect arbitrarily between the two curves as the surface forms.

In the auto industry you could not sit with the cool guys at lunch if you build models so complex. You model should be built with light surface geometry (or as light as can be). In Pro/ENGINEER we don't get isoparm display settings but we do get tangency lines. Minimize your tangency lines by being more creative with your underlying geometry. (and that does not mean using approximate curves)
 
jeff4136
thanks for these...i really like GROUP BLENDS 1 and have been trying to draw it using yours as a guide....
the spline you use in GROUP SLAB SRFS (sketch 31)is driving me up the wall, its trying to give me the smoothest curve it wants and my attempts to try and make it more like what I want (and what you did!!!!) arent working very well. did you control
the curve purely by the dimensions ? are there any tips to help
control the curve (like adding more points ) ?why did you use spline with control polygon rather
than control points ? is there any way to check the curveature of the 4
parts the curve is made from as a whole ?


any help would be appreciated ....

cheers
 
Ref http://www.mcadcentral.com/proe/forum/forum_posts.asp?TID=35 749&TPN=5
for some of the reason for using the spline Control Polygon and the
relations background (r = 3 * a^2 / b), (b = 3 * a^2 / r / 2).
It also allows a Point to Point (not Piece to Piece) Boundary Blend
Control Points option to be used. (Keep in mind the angular relation-
ships of section control polygon segments. They must be fairly
uniform to maintain minimum dihedral angles between each BB.)


In Sketch 31 the end curvature of each of the splines is
controlled by ...
dimensions (sd20, sd21, sd27), (sd60, sd62, sd67) and
sketcher relations (sd22, sd23, sd61, sd63).
Dims sd20, sd21, sd60, sd62 are 'a' values.
Dims sd27, sd67 are 'r' values.


mapkey $F1 @MAPKEY_LABEL Sketcher_Crv_Analysis;\
mapkey(continued) ~ Activate `main_dlg_cur` `Analysis.psh_skt_anl_crv`;#SCALE;1;#DENSITY;3;
will take you to (menu:) Analysis / Curvature. Any number of sketcher
entities may be selected simultaneously.


Holler back if you need anything more. I'd hate to try and unravel those
sketches, myself. I'd probably have done each individually, but I did
want to be able to see the curvature graph for all four curves at once.
It helps just to remember; 'a' and 'b' for each curve, the angle ref dims
will tell you if you are unintentionally inflecting a curve (> 180.00),
radius is controlled by sd27, sd67.



Edited by: jeff4136
 
finaly I had some time to dig this(jeff`s model) once again. I am really impressed with blends 1 and 2. The last VSS group is the sentence of all said before. It is just aweseome.

I tried to do this in another direction, to push VSS to drive section tangent to surfaces along two trajectories. It appears that with these surfaces as a base only one side allows for any results. Tangency for trajectory from inner surface provides error message. This is intresting.



I do not catch all tricks used in this model, specialy relation driven section in last VSS group needs to turn my attention on it once again.

However, the time was worth to spend with it, while I learned something new.

great stuff
 
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