POV-Ray : Newsgroups : povray.binaries.images : A head full of hair : Re: A head full of hair Server Time
1 Dec 2021 17:14:46 EST (-0500)
  Re: A head full of hair  
From: Thomas de Groot
Date: 22 Sep 2021 03:08:56
Message: <614ad688$1@news.povray.org>
Op 22/09/2021 om 02:47 schreef Samuel B.:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> Following an old discussion in 2014:
>>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.52dff97746aac96b7a3e03fe0@news.povray.org%3E/?mtop=391452
> &moff=21
>>
>> I took up Robert McGregor's code to see how it could be tweaked to
>> obtain a nice haircut. 10000 hairs were planted here. To give a rough
>> approximation: parsing took about 10 minutes and complete (stochastic)
>> render about half an hour with an i5 machine (Win10; Pov version 3.8).
>> The small highlights on the hairs resulted from a combination
>> normal/finish choices.
> 
> Hey, a fellow i5 owner :) I've got a 6500 here. It's a really good chip.
> 
<grin> I have an i5 8250 and an i7 8750 here. For some arcane and 
absolutely trivial reasons, I am using the i5 more than the i7, but 
there it is. :-)

> Ten minutes of parsing seems a little steep. Is the code having to evaluate
> every triangle, or just the scalp when choosing to place a hair? And I know
> sphere_sweeps can be pretty slow on their own, but I thought they just impacted
> the render time. Thirty minutes of render time doesn't seem as terrible as it
> could be, but it's still a little high.
> 
Not sure as I have not been monitoring closely what is going on, I guess 
it is the building of the individual mesh2 hairs which sums up. In a 
next run , I shall save/read the hair meshes and that goes faster in the 
end imo. But, not trivial, I had the laptop battery in "best battery 
life" mode; "best performance" mode is certainly faster indeed.

> Did I ever post my experiments with hair? I was using an .obj-to-.pov converter
> and trying to grow hair from a mesh. The way I had it set up was if a triangle
> was too small it only had a small chance to grow a hair, otherwise it would try
> to grow a certain number of hairs for a given triangle's area. I think I was
> using strings of cones though, and not sphere_sweeps.
> 
I don't remember, but that looks interesting, especially the approach 
using triangle sizes. I had not thought of that aspect. I simply used a 
simple trace() function on the skullcap from randomly generated points 
on an external sphere. Pretty fast by itself.

> Sam
> 
> P.S. Thanks for reminding me of Wallace and Gromit. It's a great series. Just
> watched A Close Shave. What a gem of a flick :D
> 
Oh yes, I love them. I was reminded of the scene showing Wallace tasting 
a piece of Moon (on toast) and musing: "Wensleydale?"
> 

-- 
Thomas


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