Re: [EnergyPlus_Support] Re: Shading Related Questions

["Michael J. Witte" <mjwitte@xxxxxxxx>]

> But I'm thinking about modelling the sails by joining many smaller 
> pieces of geometries to better represent the 3D structure.  That's 
> why I'm wondering if there's a limit of how small those pieces can 
> be?  Or is there a better way to tackle this problem?

It would be better to model each sail with a single polygon shading surface.  6 
vertices is probably plenty to describe this shape, but surface objects are 
"extensible" which means you can use more than 6 vertices if desired by editing 
the Energy+.idd file.

> Question regarding the "resolution" - IF we can see the shadows 
> casted by the shading device (simulated by EP), will the shadows have 
> smooth edges or rough zig-zag edges?  I know this is a weird question 

The shadow from a single shading device will be smooth.  If multipled objects 
shade the same surface, then the resulting shadow may be zig-zagged depending 
on the shape of the overlapping shadows.  But ultimately, it does not matter, 
because the result for a specific receiving surface is the sunlit area; the 
shape of that area makes no difference in the simulation.

Mike


On 5 Nov 2007 at 22:16, petervipac wrote:

> Hello Linda,
> 
> Thanks a lot for your quick response, I really appreciate that.  I am 
> trying simulate the shading effect of a 3D awning which resembles the 
> old Latin sails on ships.  Like this triangular sail in the picture 
> http://en.wikipedia.org/wiki/Sail
> 
> I could try to represent the sails using 2 big triangles initially.  
> But I'm thinking about modelling the sails by joining many smaller 
> pieces of geometries to better represent the 3D structure.  That's 
> why I'm wondering if there's a limit of how small those pieces can 
> be?  Or is there a better way to tackle this problem?
> 
> Question regarding the "resolution" - IF we can see the shadows 
> casted by the shading device (simulated by EP), will the shadows have 
> smooth edges or rough zig-zag edges?  I know this is a weird question 
> but I'm just wondering how shading is simulated by EP in addition to 
> the information mentioned in the Engineering Reference.
> 
> My appologies for not making the questions clear the first time.  I'm 
> looking forward to your answers.  Thank you for your help and 
> patience!
> 
> Regards,
> Peter Huang
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie <linda@...> 
> wrote:
> >
> > At 09:04 PM 11/4/2007, petervipac wrote:
> > 
> > >1. Does EP handle tilted/polygon shading devices (eg a 
> sail/awning)?
> > 
> > Yes.
> > 
> > 
> > >2. What is the smallest geometrical entity which EP can handle for
> > >shading calculation?
> > 
> > There is no program imposed limit.  There is likely a common sense 
> > limit and what you are trying to achieve limit.
> > 
> > 
> > >3. This is related to question 2: What is the "resolution" of EP's
> > >shading calculation?  I noticed that EP doesn't give the user any 
> sort
> > >of "mesh" control.  Does that mean it's up to the user to refine
> > >the "mesh" (geometry) themselves?
> > 
> > I'm not sure what a "mesh" is.   EnergyPlus's shading calculations 
> > result, among other things, in the calculation of sunlit areas for 
> surfaces.
> > 
> > 
> > Linda
> > 
> > EnergyPlus WebSite: http://www.energyplus.gov
> > Owner: EnergyPlus_Support list
> > Member: EnergyPlus Development Team
> > 
> > 
> > 
> > [Non-text portions of this message have been removed]
> >
> 
> 
> 
> 
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> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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