[Radiance-general] Re: Horizontal artifacts in large image

[Greg Ward]

Hi Mark,

Did you have to restart this rendering process?  The artifacts don't  
_quite_ look like an ambient calculation restart.  I have a competing  
theory, which is that a long integer is getting wrapped in the source  
testing code.  This is really a bug, but I guess it hasn't shown up  
before because no one has testing a light source 2^31 times in a single  
run.  Actually, maybe they have, but just never noticed the problem.

I'll work on a fix for this today, but obviously you're going to have  
to find another way to repair your image to meet your deadline.  Sorry  
about that.  I recommend using the -vl option to rpict and rerendering  
a portion of your image to cover up the problem areas using pcompos.   
Let me know if you need help on figuring these options out.

-Greg

> From: Mark Stock <mstock@umich.edu>
>
> Fellow Radiance users,
>
> I recently completed a large image (1.4 GB .pic file, 16k
> by 24k pixels), and it appears like there are two obvious
> horizontal bands of incorrect values (one 30% from the top,
> the other ~80% from the top). I pfilt'd the image down to
> 5% of it's original size to make the image below:
>
> http://mark.technolope.org/image/p21c_fish_take_3/redo_smooth_6/ 
> timg10_1_tw.jpg
>
> The commands that I ran were:
>
> rpict -x 16000 -y 24000 -vta -vp 0.2 0.2 -0.01 -vd 0.454 0.891 -0.08
> -vu 0 0 1 -vh 58.66667 -vv 88 -ab 1 -aa 0 -ad 16 -as 0 -dv -ds 0.1
> -dj 1.0 -t 600 -o img10_1.pic real.oct
>
> pfilt -1 -x /10 -y /10 -r 0.4 img10_1.pic > timg10_1_t.pic
> pfilt -1 -e +3 -x /2 -y /2 timg10_1_t.pic | ra_ppm | cjpeg -q 95 >  
> timg10_1_tw.jpg
>
> Does anyone know where these artifacts originate, or how to
> prevent them from appearing? I'm running the same image at
> reduced resolution right now, but final print quality is
> not going to be as I'd hoped.
>
> Mark