> "Bill Pragnell" <bil### [at] hotmailcom> wrote:
>> These look really nice, good strategy. However, does this not get memory-heavy
>> when you have a large number of buildings?
>>
> 
> Actually, I don't yet know. My original scene-- without the height_fields-- does
> suffer from a constantly climbing memory increase, the more buildings I add. I'm
> still trying to determine why that is. But my idea here is to pre-#declare the
> HFs (at their tile sizes, or as multiples of that)-- to consume memory only
> once--then instantiate them into the scene for many building repetitions via
> #while loop (and maybe using simple clipped-by planes to then slice-and-dice
> some of the windows off to get *whatever* random building-face-sizes I want.)
> Although, I haven't yet tried this scheme 'at scale'.
> 
> BTW, I eventually want to have as many as 50 different window styles-- thus 50
> trios of images to work with.
> 
> The idea common to both my scenes is to pre-#declare all the
> pigment{image_maps...} too,  before using them in various places in the
> #while-loop code-- which does (or should!) save memory as well.
> 
> But there is a certain block of code *within* the #while-loop-- an image_pattern
> block, common to both scenes-- that may be the problem when finally applying the
> window *reflections* (via the hold-out mattes) to the buildings.
> Here's a simplified demonstration, using only one style of HF tile:
> 
> --- *before* the #while-loop repetitions, to save memory---
> #declare PIG_1A = pigment{image_map{...}} // the photo tile of the building face
> #declare PIG_1B = pigment{image_map{...}} // the HF-artwork tile
> #declare PIG_1C = pigment{image_map{...}} // the hi-contrast hold-out matte
> // tile for the window reflections (which actually can't be used-- see below)
> #declare HF_1 = height_field{PIG_1B... scale <...>};  // the original HF
> 
> -- *within* the #while loop, to make lots of these particular buildings---
> #declare FINAL_BUILDING_FACE =
> union{... another while loop to make random height-and-width repetitions
> // of the original HF tile)...}
> ........
> object{FINAL_BUILDING_FACE
> texture{
>      image_pattern{
>      jpeg "building windows 1 holdout.jpg" //  the *actual* high-contrast
>      // hold-out  matte for the window reflections, not PIG_1C. And no 'once'
>      // keyword, BTW.
>                   }
>       scale <432,724,1>/724 // pixel dimensions of hold-out matte (actually
>       // of all 3 images)
>       texture_map{ // two identical pigments, but one having REFLECTION.
>                 [0.45 pigment{PIG_1A} finish{...}]
>                 [0.55 pigment{PIG_1A}finish{...reflection {REFLECT_AMT}}
>                  }
>         }
>       }
> 
> As far as I've been able to work out, there is no way to substitute PIG_1C or
> something else for...
>                     jpeg "building windows 26 HO.jpg"
> 
> ......in order to save on *memory*.
> 
> By itself, the latter isn't an 'Rvalue' that can be pre-#declared. (Neither is
> the small image_pattern block itself.) Which means that the hold-out image is
> constantly reloaded into memory, maybe hundreds of times. And this is for only
> ONE building style.
> 
> I've come up with only two tricks that actually work, if only code-wise: a
> #macro substitution of "building windows 26 HO.jpg", but which basically just
> inserts a text string, with no instantiation of the actual image. And a #macro
> for
>          jpeg "building windows 26 HO.jpg"
> but I don't really know if that 'instantiates' the image (i.e., 'caching' of the
> macro contents.) I don't think so.
> 
> This could be a big part of why the memory footprint of the scene increases, and
> I don't yet know how to work around it-- that is, without a 'brute-force' method
> of pre-#declaring 50 such constructs as individual texture blocks!
> 
> 
> 
> 
> 
This may help:
Start with a reflective box for the buildings.
Place your tiles so that the windows parts lies just under the 
reflective box.
The box will hide the "bottom" of the hight_field, and the raised parts 
of the hight_field will hide the mirror outside of the windows.
Place a roof box on the top that will hide the mirror box.

The inside, mirror, box should have an ior and use fresnel reflection. 
You also can give it some normals perturbation.

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