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Strategy for 3D Church Building


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I'm surveying medieval churches and using my survey data to build their interiors in 3D in VW 10.1. These interiors are very complex, using large, complicated mouldings.

My question is, what sort of strategy should I use to generate the smallest possible file sizes while maintaining a fairly high degree (within 5mm) of accuracy?

I have been creating moulded surfaces by extruding a 2D polyline profile along a 2d polyline path (sometimes a 2D polygon path as well). This usually works out well, but when I assemble all the members of the building the resultant file is 250MB and growing - which is difficult for my computer (G3 iBook 700mhz 256RAM) to handle.

Also, when I extrude a 2d Polyline I have not been able to get it to render correctly - when I render in unshaded polygons no lines - I get a mass of confusing geometry shown. Are 2D polylines good for this sort of thing or should I first convert to NURBS curves - what is the advantage of converting to NURBS?

As you can tell, I'm a little inexperienced and any advice would be much appreciated. Ideally I'd like to export a model of a church to VRML (which, I know, will greatly reduce realism and accuracy - but hopefully improve 'explorability').

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  • 3 weeks later...
  • Vectorworks, Inc Employee

Hello Anthony:

quote:

I have been creating moulded surfaces by extruding a 2D polyline profile along a 2d polyline path (sometimes a 2D polygon path as well). This usually works out well, but when I assemble all the members of the building the resultant file is 250MB and growing - which is difficult for my computer (G3 iBook 700mhz 256RAM) to handle.


Are you making repetitive items into symbols? That can greatly reduce the file size for repetitive geometry.

quote:

Also, when I extrude a 2d Polyline I have not been able to get it to render correctly - when I render in unshaded polygons no lines - I get a mass of confusing geometry shown. Are 2D polylines good for this sort of thing or should I first convert to NURBS curves - what is the advantage of converting to NURBS?

As you can tell, I'm a little inexperienced and any advice would be much appreciated. Ideally I'd like to export a model of a church to VRML (which, I know, will greatly reduce realism and accuracy - but hopefully improve 'explorability').


If you don't have RenderWorks, OpenGL should provide a better rendering than the polygon modes, unless you want to see the edges. If you think the polygon rendering is incorrect, please call tech support and find out if this is a bug we should be fixing. Extruded or swept 2D polylines should be perfectly fine for rendering. The OpenGL and RW modes can generate NURBS surfaces from them for rendering purposes, so you are not losing anything by not modeling directly with NURBS.

I would recommend modeling with the simplest techniques that provide the geometry you need, from solid primitives like spheres, extruded 2D cross sections, circular sweeps, and on up to more sophisticated modeling tools like extrude along path, revolve with rail, and freeform NURBS modeling only if needed.

The OpenGL rendering mode will render your model interactively while uding the Flyover or Walkthrough tools, which can be great for exploring the model. Also, you can define multiple views with the Saved Sheets control at the bottom of the window (next to the Fit to Object and Fit to Page buttons) then create a Quicktime animation from the saved views (Model->Create Animation, choose to create a Path instead of Orbit).

Does this help?

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  • 3 weeks later...

Dear Dave,

Thanks very much for these tips. They are helpful. As I've been working more with the model, I've been learning more, and can use your tips well. I have a couple of more specific questions:

Are you making repetitive items into symbols? That can greatly reduce the file size for repetitive geometry.

I do have repetitive items as symbols. The file size still seems large - the symbols are 3D only (I haven't quite figured out how to make them hybrid - I've tried selecting the objects in Top/Plan View and choosing Create Symbol to create a hybrid but this seems to only make a 3D symbol). Would hybrid symbols reduce the file size?

If you don't have RenderWorks, OpenGL should provide a better rendering than the polygon modes, unless you want to see the edges. If you think the polygon rendering is incorrect, please call tech support and find out if this is a bug we should be fixing.

I do have RenderWorks, and I've gotten OpenGL to work. However, when I render an object created from extruding along a path as a hidden lines render, I get a lot of extraneous geometry shown, especially in areas of curves. Is this a common problem?

Thanks again for your help.

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When the shape of your objects is satisfactory (and only then), you can always remove the construction history. Use the command "Convert to Generic Solids" to achieve this. This is only possible from 10.5 onwards.

If VectorWorks refuses to execute the command - and you will run into this if you would try to convert an extrusion along path - you can always transform your object: first convert to NURBS, then ungroup, and then add solids. The new solid object can without a problem be converted to a generic solid.

Cheers,

BaRa

[ 01-03-2004, 03:33 PM: Message edited by: BaRa ]

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  • Vectorworks, Inc Employee

Hello Anthony:

If the symbol has any 2D objects in it then it will automatically become a hybrid symbol. Only the 2D parts will show in plan, and the 3D parts in other projections.

The quickest way to balloon VW file size is through image-based textures, image objects, or image fills. It is otherwise very difficult to make a very large VW file through modeling alone, unless the model is converted to a large mass of polygons. You may try using the Purge Unused Objects menu item to flush out any textures that aren't being used in the drawing.

Try setting a non-zero value in the Document Preferences->Line Render->Smoothing Angle field. That should reduce the number of lines in Hidden Line render mode.

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