POV-Ray : Newsgroups : povray.advanced-users : "f_r" function help Server Time: 18 Jun 2019 17:06:35 GMT
 "f_r" function help (Message 1 to 3 of 3)
 From: Mike Horvath Subject: "f_r" function help Date: 9 Mar 2017 00:44:56 Message: <58c0a588\$1@news.povray.org>
```I want to use the "f_r" function to color a sphere from black (inner) to
white (outer). However, there needs to be a hole in the center equal to
1/7 of the sphere's radius, and the gradient must start at this location
instead of the sphere's exact center.

Here is what I have:

pigment
{
function {f_r(x,y,z) * 6/7 + 1/7}
pigment_map
{
[0 color srgb 0]
[1 color srgb 1]
}
}

But the results are not correct.

How do I accomplish this? Thanks!

Mike
```
 From: Alain Subject: Re: "f_r" function help Date: 9 Mar 2017 16:31:05 Message: <58c18349\$1@news.povray.org>
```Le 17-03-08 Ã  19:45, Mike Horvath a Ã©crit :
> I want to use the "f_r" function to color a sphere from black (inner) to
> white (outer). However, there needs to be a hole in the center equal to
> 1/7 of the sphere's radius, and the gradient must start at this location
> instead of the sphere's exact center.
>
> Here is what I have:
>
> pigment
> {
>     function {f_r(x,y,z) * 6/7 + 1/7}
>     pigment_map
>     {
>         [0 color srgb 0]
>         [1 color srgb 1]
>     }
> }
>
> But the results are not correct.
>
> How do I accomplish this? Thanks!
>
>
> Mike

function {f_r(x,y,z)}
pigment_map{
[1/7 rgbt 1] // optionnal
[1/7 srgb 0]
[1   srgb 1]
}

Fully transparent from the center up to 1/7 th of the radius.
Then, black at 1/7 th of the radius.
```
 From: Mike Horvath Subject: Re: "f_r" function help Date: 10 Mar 2017 07:18:14 Message: <58c25336\$1@news.povray.org>
```On 3/9/2017 11:31 AM, Alain wrote:
> Le 17-03-08 Ã  19:45, Mike Horvath a Ã©crit :
>> I want to use the "f_r" function to color a sphere from black (inner) to
>> white (outer). However, there needs to be a hole in the center equal to
>> 1/7 of the sphere's radius, and the gradient must start at this location
>> instead of the sphere's exact center.
>>
>> Here is what I have:
>>
>> pigment
>> {
>>     function {f_r(x,y,z) * 6/7 + 1/7}
>>     pigment_map
>>     {
>>         [0 color srgb 0]
>>         [1 color srgb 1]
>>     }
>> }
>>
>> But the results are not correct.
>>
>> How do I accomplish this? Thanks!
>>
>>
>> Mike
>
> function {f_r(x,y,z)}
> pigment_map{
>  [1/7 rgbt 1] // optionnal
>  [1/7 srgb 0]
>  [1   srgb 1]
> }
>
> Fully transparent from the center up to 1/7 th of the radius.
> Then, black at 1/7 th of the radius.

Thanks! That works.

Mike
```