Multipatch to dxf

[mia]

Hi,
Im trying to convert a multipatch shapefile (representing houses) into dwg/dfx. When I open the dxf file in Autodesk Map 3D some of the lines constructing the walls and the roof has dissapeared. When I open the dxf file in Sketchup or Autodesk Vis 4 some of the faces are "inside out" and therefore invisible or in a different coulour. I don't think the multipatch faces has a determined direction (normal) and thats probably why (?).Is there a way to solve this problem?
Thanks in advance
/Maria

[GuthCAD Software Support]

Hi mia,

1. Would it be possible for you to email me the house shapefile so that we can investigate the missing lines?

(click on the 'GuthCAD Software support' at the top of this reply, and select 'Send email to GuthCAD Software support' from the dropdown menu)

2. Re. normals, it could be that Arcv2CAD has not paid attention to the direction of vertices when breaking up the multipatch 'triangle strip' and 'triangle fan' sub-types. We will investigate further on that, and let you know. (I will post a reply to this thread.)

thanks,
Paul G

[GuthCAD Software Support]

Maria,

Hi again.

We have posted a software update which will hopefully address the problems you reported. The update is version 3.2 E.122 here.

http://www.guthcad.com/arcv2cad_beta.htm


1. It should fix the missing lines. (This could occur for multi-patch sub-types 'triangle strip' or 'triangle fan'.

2. Face vertices for 'triangle fan' and 'triangle strip' sub-types are now output in a consistent direction, and also will keep the defined direction for multipatch 'ring' sub-types.

Re.
> When I open the dxf file in Sketchup or Autodesk Vis 4 some of the faces are "inside out" and therefore invisible or in a different colour. I don't think the multipatch faces has a determined direction (normal) and thats probably why (?). Is there a way to solve this problem?

I don't know specifically about Sketchup or Autodesk Vis 4, but at least in AutoCAD 2000, one of the Render options is to 'Discard back faces'. If this option is unchecked then rendering will occur correctly whether or not the normal is facing 'inside' or 'out', the only penalty is the speed of rendering. But unless your model is very large, this should not be an issue. Hopefully there is a similar option in Sketchup or Autodesk Vis 4 (we don't have the software, if anybody can confirm please let me know.)

thanks,
Paul G

[Kal]

Maria,


Re.
> When I open the dxf file in Sketchup or Autodesk Vis 4 some of the faces are "inside out" and therefore invisible or in a different colour. I don't think the multipatch faces has a determined direction (normal) and thats probably why (?). Is there a way to solve this problem?

I don't know specifically about Sketchup or Autodesk Vis 4, but at least in AutoCAD 2000, one of the Render options is to 'Discard back faces'. If this option is unchecked then rendering will occur correctly whether or not the normal is facing 'inside' or 'out', the only penalty is the speed of rendering. But unless your model is very large, this should not be an issue. Hopefully there is a similar option in Sketchup or Autodesk Vis 4 (we don't have the software, if anybody can confirm please let me know.)

thanks,
Paul G

my knowledge in Sketchup 4.0 about the back faces:(extract from the help)

Faces in SketchUp have a front and a back side. Each side of a face can have a material assigned to it. However, when exporting SketchUp geometry to a file format that only supports single-sided faced polygons (like DXF, DWG, and 3DS), it becomes important to know which side of the face will be exported. Use the Reverse command to flip the front and back sides of the selected face as needed.

Should help Maria...(Autodesk ViZ 4 or above use 3DS format)

Thanks,

Kal