POV-Ray : Newsgroups : povray.bugreports : CLipka: Possible BUG Found!!! :-) : Re: CLipka: Possible BUG Found!!! :-) Server Time: 21 Sep 2019 06:41:55 GMT
  Re: CLipka: Possible BUG Found!!! :-)  
From: Sven Littkowski
Date: 13 Feb 2016 20:41:59
Yes, and that is, where my own boundaries begin: functions. That is a
field, in which I was never good (though I am excellent in some other
fields)...

But yes, I understand, that for a cylinder I have to work with 3.14, due
to its shape.

Once I manage to have the heightfield in the cylinder, I will work then
on a texture, and then on plants and finally on buildings.

----------------------------------

On 13.02.2016 11:21, Kenneth wrote:
> Sven Littkowski <jam### [at] yahoocom> wrote:
>> If I understand correctly, the side ratio of the image has to be 3.14 x
>> 1.0, correct? If I have an image 10,000 pixels high, the width needs to
>> be 31,400 pixels.
> 
> Yes. But you don't need to be 'locked in' to that ratio. Once you understand the
> HF_Cylinder behavior better, you can change that. For example, in the code I
> posted, I deliberately made the cylinder 1.7-units high (not 1.0) while also
> using a 'standard' pi:1-ratio image-- to show how you can get the 'image
> function' to still look correct on the heightfield. But if you really want a
> taller cylinder than 1.0, the original image_map should be *created* taller as
> well-- then you would likewise change the scale somewhere in the HF_Cylinder to
> make sure everything looks correct.
> 
> By the way, if you want to apply the same image_map as a PIGMENT to your
> heightfield, turn on 'UseUVtexture' in the macro. To save on memory and parse
> time, pre-#declare the image_map like this...
> 
> #declare CYL_PIGMENT =
>      pigment{
>            image_map{jpeg "my_image.jpg"  once interpolate 2}
>             };
> 
> Then you can use it as your HF function...
> 
> #declare Fn_1 =
> function{
>  pigment{
>   CYL_PIGMENT
>   //scale <-1,1,1>
>   //translate <1,0,0>
>   }
>  }
> 
> ..... and also in your texture definition.
> 
> An interesting fact: When using the 'once' keyword in the image_map, AND also
> applying it as a texture/pigment, the HF_Cylinder only shows up where the
> pigment is applied-- any remaining part of the cylinder disappears. It's as if
> the other parts of the cylinder have a totally transparent texture on them (even
> though the original image has no alpha-channel.)
> 
> By the way: In my code example, I wrote this code line...
> 
> HF_Cylinder( function{Fn_1(x,y*1.7,z).gray}
> 
> If you haven't worked with functions before, what that *really* means is
>                           <x,y/1.7,z>
> 
> Multiplication and division are written the *opposite way* in functions (or
> 'inverse' way) of what you would normally write.
> 
> 
> 
>


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