Hard work on a bridge


#1

Hi. I’m working on a bridge project. I had real problems to model it. It’s a bridge with different cross sections in size (with non linear transitions) and with a 3d spline generation axis. I finally decided to use a really complex sweep object with many (70) given planar cross sections in Autocad. I got a “dirty” model, hard to work with and with many problems with faces. The question is simple: how can i do this? Is Rhino the answer?

I have seen many bridge tutorials for different software packages, but it’s always a really simple bridge!!(constant cross section in size).
I want to render it on 3d Max.


(David Cockey) #2

What does the bridge look like? Do you have equations for the cross-sections and transitions?


#3

There’s lot of things you can do:
First solution could be to use the networksrf tool, isn’t my preferred one but works greatly in this situation.
By changing the tolerances number you can get lighter or dense srf.
If this doesn’t fit your needs you have to go for a more complex modeling, by subdividing the sections in “equal” parts according with the vertices and sweep each part alone.
Have a look to an example of your model and sections could help us to help you :wink:


(Pascal Golay) #4

Can you please post the file here, or to tech@mcneel.com if it is confidential? Probably not the whole bridge- just export the inputs to the object you are asking about.

thanks,

-Pascal


#5

Hi guys, sorry for the delay and many thanks for your help.
This 4 images are from the “dirty model”.
Differences in cross sections are hard to see in the images, but I swear they are. The road is slimmer at the beginning of the bridge for example, and the barrier is simple at the beginning and then becomes double.

Thank you all


#6

Very simple shape, at least for an old user.
Best , for me, would be to subdivide the shape in simpler “boxy” pieces.
Not good idea to use the section as they are from autocad. Architect drawing in 2D are used to make many mistakes!


(David Cockey) #7

The road and roadbed appears to have a constant cross section and flows along a curve. I would create the centerline curve for the road, create a cross-section curve or planar surface for each element of the road and roadbed, and then sweep the cross-section of each element along the centerline curve.

The piers under the roadbed appear to be constant thickness in the longitudinal direction. My guess is each pier has the same profile, truncated to the appropriate height. I’d create a curve of the transverse profile, extrude the profile curve into a solid. Then I’d copy the pier to the desired locations and orientations and trim to the required height.

The towers above the road also appear to be constant thickness in the transverse direction. I’d create a curve of the longitudinal profile, extrude it into a solid, and then copy to the appropriate locations.

The “wings” from the center piers could be created using a simple set of lines defining the edges between the piers and the roadbed.

The cables would be simple pipe elements.

For an experienced Rhino modeler this should be a relatively quick job. For a novice user it would take a little longer but nothing “fancy” would be needed.


#8

Thank you for your help david, but the road and roadbed don’t have constant cross section. (The images do not help to see it, I know!). That’s the reason not to do a sweep object.Cables piers and towers are obviously not a problem. The problem is the bridge itself as it is defined by different cross sections (with smooth transitioning from one to the following) along a 3d spline.

-------- Mensaje original --------
De: davidcockey
Fecha:30/08/2014 04:27 (GMT+01:00)
Para: maastiz@estudioastiz.com
Asunto: [McNeel Forum] Hard work on a bridge

davidcockey

August 29

The road and roadbed appears to have a constant cross section and flows along a curve. I would create the centerline curve for the road, create a cross-section curve or planar surface for each element of the road and roadbed, and then sweep the cross-section of each element along the centerline curve.

The piers under the roadbed appear to be constant thickness in the longitudinal direction. My guess is each pier has the same profile, truncated to the appropriate height. I'd create a curve of the transverse profile, extrude the profile curve into a solid. Then I'd copy the pier to the desired locations and orientations and trim to the required height.

The towers above the road also appear to be constant thickness in the transverse direction. I'd create a curve of the longitudinal profile, extrude it into a solid, and then copy to the appropriate locations.

The "wings" from the center piers could be created using a simple set of lines defining the edges between the piers and the roadbed.

The cables would be simple pipe elements.

For an experienced Rhino modeler this should be a relatively quick job. For a novice user it would take a little longer but nothing "fancy" would be needed.


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(David Cockey) #9

Non-constant cross-sections of the road and roadbed should not be a problem. The sweep commands in Rhino work with multiple cross-sections, smoothly transitioning between the cross-sections.

How is the variation of the cross-sections defined?