[Radiance-general] Creating a void in a wall

[Greg Ward]

If you use antimatter, you will need to create a box that cuts through the wall to make an opening, creating more geometry than simply making an opening in the wall in the first place.

Using mixfunc, you can alternate materials in the wall, but if the wall has thickness, you will end up seeing "into" the wall this way, unless you also insert some sill geometry.  Again, it ends up being easier to create the opening for a thick wall.

Best,
-Greg

> From: "Ehsan M.Vazifeh" <em.vazifeh at gmail.com>
> Date: January 29, 2014 4:42:44 AM PST
> 
> Thanks for your early respond Lars.
> 
> If I understand correctly to create a window within the wall I need to use a mixfunc, because using antimatter will make everything invisible, right?
> 
> Cheers, Ehsan
> 
> 
> On Wed, Jan 29, 2014 at 1:18 PM, Lars O. Grobe <grobe at gmx.net> wrote:
> Hi Ehsan,
> 
> nothing is impossible with Radiance ;) You can get a hole into your wall without modifying the underlying geometry of the wall polygon. One way is to cut out the opening with a box of material antimatter. Everything within that box will become invisible. This means that you can also not place window frame and glass inside. The second option is to apply a mixfunc modifier to your wall. At locations defined by a simple function, the material will be "air" (e.g. void, or trans with pure specular transmission), everything else will be your wall material.
> 
> But: you likely introduce later problems when modeling that way. Once that you have overlaps of your invisible, but still existing wall polygon with other geometry (window pane, bsdf or illum, ..) you will get strang results which are hard to debug. I would not recommend this for a simple wall. There are cases where this may make sense, though - e.g. if you want to cut a hole into a sphere, you can either use antimatter or mixfunc into a sphere primitive with few lines of Radiance scene description, or you have to mesh the hole sphere object... possibly leading to a megabyte of triangles...
> 
> Cheers, Lars.
> 
> > Dear All,
> >
> > Is it possible to create a void in a wall instead of creating polygons around a void?
> >
> > For instance:
> > for creating a window we can generate polygons surrounding the window and then a polygon which refers to glass. now I want to know instead of doing that is it possible to define a wall as a polygon and create a window on the wall without manipulating the wall's polygon.
> >
> > It might have a simple solution.
> >
> > Best Regards,
> >
> > Ehsan
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> -- 
> E. M. Vazifeh
> Project Assistant
> Department of Building Physics and Building Ecology
> Vienna University of Technology
> Karlsplatz 13, A-1040 Vienna, Austria
> Tel +43 1 58801 27003
> Fax +43 1 58801 27093
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