> clipka <ano### [at] anonymousorg> wrote:
>> Am 14.01.2013 01:55, schrieb Woody:
>>> I'm having an issue which I'm hoping someone can give me some insight into.
>>
>> You seem to have some misconceptions about how POV-Ray's CSG and
>> handling of transparent textures cooperate. Because as a matter of fact
>> they don't.
>>
>> First it is crucial to understand that POV-Ray renders /surfaces/. This
>> is true even for "solid" objects: The concept of being "solid" only has
>> a meaning in the context of "Constructive Solid Geometry" (CSG)
>> intersections and differences, where the volumetric definitions of
>> objects are used to mutually determine which sections of the other
>> objects' surfaces are to be rendered; the only reason why this doesn't
>> lead to visible holes in the geometry is because the holes that are
>> ripped open in the surface of one object are precisely filled with the
>> remaining surfaces of the other objects.
>>
>> When applying partially transparent textures to an object, other rules
>> apply: Textures define the colors (and transparency values) to use when
>> an object's surface is rendered, but they don't define any surfaces
>> themselves. Textures can be used to suppress all or part of an object's
>> surface (by using a transparent pigment), but they can't define new
>> surfaces: They are unable to fill the holes they rip open.
>>
>> You /can/ define a shape based on a transparent texture, but this
>> requires the use of the slow isosurface object.
>
> I stand corrected. Thanks for clarifying.
>
> Wouldn't there be a way though to program the ray so that, given that the ray
> has intersected an surface with transparency turned on, but not yet hit a
> surface transparency turned off, it would be able calculate which pigment would
> occurr at each point of calucation in between based on the supplied UV values?
>
> -Jeff
>

Unless your object is filled by some media, or use colour fading, there 
is no colour evaluation done between the surfaces.
Colour fading can only deal with uniform tints, making it unsuitable for 
your intended use.
You can use media. The media can't exist inside your object unless you 
add the "hollow" attribute to the object.
You can use your image to modulate the media density, but can't UV map 
it for that purpose. The media will need to have a high density and will 
make the object slower to render, but only in areas where you can see 
inside due to the transparency. You need to use scattering media.
Please read the section about media in the documentations.



Alain

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