POV-Ray : Newsgroups : povray.pov4.discussion.general : Basics. : Re: Basics. Server Time
19 Jun 2021 16:53:39 EDT (-0400)
  Re: Basics.  
From: Alain
Date: 3 Mar 2014 20:03:53
Message: <53152679@news.povray.org>
> OK, I get the impresion that this render engine will give random attibutes to
> textures in a model for render, or at least seems to.  Forgive my ignorance
> because I cannot find the information I am looking for and to be honest bulletin
> boards are a bit 1980.  How do I associate an attribute I want rather than a
> random type?  How do I associate a material with bump or a bump map?
>
> Other than allow the program to do what it wants, how do I actually achieve
> anything with pov-ray?
>
> I know, search, done and the results are very hit and miss.  To be honest I
> cannot see the point of a render program with randomly associated material
> attributes.  Have a good day folks.
>

There are NO material attributes having any random attributes anywhere 
unless you explicitely introduce some random elements in your 
textures/materials. That "random" element is realy pseudo-random and the 
results are reproductible. Even turbulence is pseudo-random. The ONE AND 
ONY element of the finish that IS truly random, is crand. The only other 
place where you can have any truly random factor, is when you use jitter 
in an area_light, photons shooting, media sampling or antialiasing.

In POV-Ray, patterns, textures, materials are defined in 3D space and 
your objects are "carved" from that. If you translate, scale or rotate 
an object BEFORE you apply the material, the object will get transformed 
relative to the material and it's aspect will change accordingly. If you 
do the transformation AFTER the material is applyed, then, the material 
will follow your object.

To apply some bumpyness, you should use the normals attribute to the 
finish of the material. It can be in the form of a pattern or a user 
provided image serving as a bump_map.

Source images, as image_map, are mapped from <0,0> to <1,1> on the X-Y 
plane and repeated infinitely. They extend along the Z axis to infinity.
You need to scale them properly, and may need to rotate them if needed.

Most primitives DON'T use, nor support, UV mapping. Read the 
documentation to learn whitch ones DO support UV mapping.



Alain


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