POV-Ray : Newsgroups : povray.beta-test : Ambient and diffuse for include files? Server Time
7 Oct 2022 09:16:09 EDT (-0400)
  Ambient and diffuse for include files? (Message 1 to 4 of 4)  
From: Cousin Ricky
Subject: Ambient and diffuse for include files?
Date: 7 Mar 2022 13:33:29
Message: <62264ff9$1@news.povray.org>
There are gaps in SDL's ability to query the state of the render, and
one of these is the default finish.  This is a problem for defining
certain library textures when radiosity is not used, as include files
have no access to the scene's lighting conditions.  This is the case
with several of the standard include files.

For a 100% diffuse texture, this is easily solved by omitting an ambient
from the finish, and setting a default ambient prior to including the
file that defines the texture; the textures in woods.inc are like this.
At the other extreme, a 100% specular texture, such as a pure metallic
texture, would have both ambient and diffuse set to zero.

But what about a texture that is, say, half metallic?  In that case, the
diffuse and ambient need to be halved.  But halved from what?  While it
is possible to override a finish ambient, I feel it is an unreasonable
burden on the user to have them figure out what ambient is appropriate
for each library texture.

The solution I used for RC3Metal was to have the user declare variables
with the scene's default ambient and diffuse.  But to implement this
solution over many include files would cumbersome for the user.  These
standard include files all set non-zero ambients on declared textures:
  glass_old.inc
  golds.inc
  metals.inc
  stones1.inc
  stones2.inc
  textures.inc

(Files finish.inc, skies.inc, and stars.inc also set non-zero ambients,
but these should really be converted to emission.)

One way to solve this would be to declare a single pair of variables
that would be used by all six include files.  Third party include files
would be encouraged to access these variables.  What do you think of
this proposal?  Does anyone have a better idea?


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From: Thomas de Groot
Subject: Re: Ambient and diffuse for include files?
Date: 8 Mar 2022 02:23:28
Message: <62270470@news.povray.org>
Op 07/03/2022 om 19:33 schreef Cousin Ricky:
> [snip] >
> One way to solve this would be to declare a single pair of variables
> that would be used by all six include files.  Third party include files
> would be encouraged to access these variables.  What do you think of
> this proposal?  Does anyone have a better idea?

I am certainly no expert at all on this, but it seems a reasonable 
option to me while easiest to implement.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Ambient and diffuse for include files?
Date: 8 Mar 2022 06:45:00
Message: <web.622740a5485c224d1f9dae3025979125@news.povray.org>
Cousin Ricky <ric### [at] yahoocom> wrote:

> One way to solve this would be to declare a single pair of variables
> that would be used by all six include files.  Third party include files
> would be encouraged to access these variables.  What do you think of
> this proposal?  Does anyone have a better idea?

Absent my current ability to formulate ways other than that one, I'd say that
starting all of those include files with an #include statement that references a
master include would be a good way to do it, in case any future tweaks happened.

Pre-coffee brain is thinking that the textures ought to be written as macros
that return a texture.
Why?
Then you could declare a secondary pair of values to hold "current" values while
retaining the default master values.   Then the user could use the stock
textures with the unaltered default master values, or override them by
redeclaring the "current" values.

Hope that makes sense.

Having some sort of "starter" include, or basic scene file template, or helper
libraries for new users has been intermittently discussed and worked on.
Perhaps as a means to implement, document, and standardize things going forward
from 3.8 to 4.0, you could take this value-pair idea and put that in a
default_values.inc or something that would always get included first thing.
Even after 30 years, we're still grappling with coincident textures, and so I
always define an E value, which is usually 0.000001 to make things bigger or
smaller by that much.  Having that value defined also serves as a reminder when
I'm doing differences, etc.


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From: jr
Subject: Re: Ambient and diffuse for include files?
Date: 8 Mar 2022 09:15:00
Message: <web.62276406485c224ded36e5cb6cde94f1@news.povray.org>
hi,

Cousin Ricky <ric### [at] yahoocom> wrote:
> ...
> One way to solve this would be to declare a single pair of variables
> that would be used by all six include files.  Third party include files
> would be encouraged to access these variables.  What do you think of
> this proposal?  Does anyone have a better idea?

given that the typical use case is a scene file doing '#include's, a single
"guard" would be nice + easy from the user point of view.


regards, jr.


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