Hi,
I'm using values below for higher quality render of a kitchen. I copied them off
the net somewhere. For normal quality render I skip below code and use regular
light values of povray. Now what I want to do is put up a slider bar from
1 to 5 and change render quality.

1- Which value/values below needs to be changed to match the slider?
2- Is this the code below right for  higher quality render?

 global_settings {adc_bailout 0.003922
 ambient_light <1.0,1.0,1.0>
 assumed_gamma 1.9   hf_gray_16 off
 irid_wavelength <0.247059,0.176471,0.137255>
 max_intersections 64   max_trace_level 10
 number_of_waves 10
 radiosity {brightness 0.3
 count 100 distance_maximum 0.0
 error_bound 0.4 gray_threshold   0.5
 low_error_factor 0.8 minimum_reuse    0.015
 nearest_count    6 recursion_limit  1

Thank you very much.

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> Hi,
> I'm using values below for higher quality render of a kitchen. I copied them off
> the net somewhere. For normal quality render I skip below code and use regular
> light values of povray. Now what I want to do is put up a slider bar from
> 1 to 5 and change render quality.
> 
> 1- Which value/values below needs to be changed to match the slider?
> 2- Is this the code below right for  higher quality render?
> 
>  global_settings {adc_bailout 0.003922
With reflections and transparence. Can have some effect on the quality. 
Smaller values gives more acurate results, but take longer and may not 
be obvious. You can often use a larger value to get faster renderings 
with no realy dicernable effect on the quality.

>  ambient_light <1.0,1.0,1.0>
NO effect on the quality. Usefull to alter the colour of objects having 
a non-zero ambient finish. Artistic side.

>  assumed_gamma 1.9   hf_gray_16 off
REMOVE assumed_gamma. It is been phased out and will NOT be supported in 
any future version.
hf_gray_16 is user to create a special gray scale image usefull to 
generate hightfields.

>  irid_wavelength <0.247059,0.176471,0.137255>
Not a quality parameter.

>  max_intersections 64   max_trace_level 10
max_intersections is rarely used and normaly don't need to be changed 
from the default value. You can leave out.

max_trace_level dictate how many surfaces you can encounter befor 
stoping and returning black. Importent quality parameter whenever you 
have several reflection and transparences. Works with adc_bailout. Can 
be set to up to 255.

>  number_of_waves 10
Not a quality affecting parameter. Affect the waves and ripples patterns.

>  radiosity {brightness 0.3
Brightness affect the overall brightness of the radiosity scene. Not a 
quality parameter. Lower if the scene is to bright, increase if the 
scene is to dark.

>  count 100 distance_maximum 0.0
count is a very importent quality factor in radiosity. Default to 35. 
Should not be set lower than that. Highest possible value = 1600.

distance_maximum IS NOT a proper key word and is NOT supported by any 
official versions of POV-Ray. It will cause an undefined user variable 
fatal error and abort the parsing of the scene.

>  error_bound 0.4 gray_threshold   0.5
error_bound is another very importent quality parameter. Default to 1.8.
A lower value normaly demands that you increase the count value. Have an 
effect to the "deepness" and sharpness of the shadows.

gray_threshold affect the saturation of the radiosity effects. More 
artistic than quality.

>  low_error_factor 0.8 minimum_reuse    0.015
Both affect the quality.
low_error_factor affect the error_bound during the last pretrace step. 
Usualy, only a slight effect.
minimum_reuse sets the relative distence between radiosity samplse to be 
reused and averaged toghther. Don't set to a value larger than 0.18. 
Smaler value often require a higher count.

 >  pretrace_start 0.08 pretrace_end 0.04
Controls the pretrace passes. can be used to reduce some artefacts. The 
value is a ratio of the horizontal dimention of the image been rendered.
There is no point to set pretrace_end to anything lower than 
2/image_width meaning a last pretrace step of 2x2 pixels tiles.

>  nearest_count    6 recursion_limit  1
nearest_count helps to get smoother results. Maximum value = 20

recirsion_limit set the number of radiosity bounces. Depends on your 
particular scene. Normaly, 1 is good for most exterior scenes, but some 
may need a value of 2 or 3.
Interior scenes ferquently need a value of 2 to 4. If the radiosity 
evvect need to take into acount something behind a pane of glass, and 
you do a single pass rendering, you need at least a value of 3, 2 levels 
been used to get through the pane.

> 
> Thank you very much.
> 
> 
> 



Alain

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optima schrieb:
> 1- Which value/values below needs to be changed to match the slider?
> 2- Is this the code below right for  higher quality render?
> 
>  global_settings {adc_bailout 0.003922

This /could/ be made "slidable".

>  ambient_light <1.0,1.0,1.0>

For high-quality renders you'll want to use radiosity; when using 
radiosity, you'll want ambient_light to be 0, unless you've made sure 
that all textures have ambient 0 except for those that should appear to 
be "glowing".

>  assumed_gamma 1.9

This should always be the same. You should also check whether you really 
want to use 1.9, and not 2.2 instead (which is the de-facto standard for 
images to be published on the net, for instance).

 >  hf_gray_16 off
>  irid_wavelength <0.247059,0.176471,0.137255>
>  max_intersections 64

Always same.

 >  max_trace_level 10

If you're using a lot of reflective surfaces, you may want to increase 
this to, say, 25. Sliding is a good idea.

If you use POV-Ray 3.6 (or even lower) to render, you virtually /must/ 
set this to a rather high value when using radiosity as well as any 
reflective or refractive materials, or you'll inevitably get black 
splotches scattered across the room. This problem has been solved in 
current 3.7 betas.

>  number_of_waves 10

Keep unchanged.

>  radiosity {brightness 0.3

brightness 1.0 should give more realistic results (at least 
theoretically; verifying this is still on my agenda). Doesn't affect 
speed, but may have to be tuned to recursion_limit (low recursion_limit 
values may need a slightly increased brightness).

>  count 100

You definitely want to increase this as high as 1600 in top-quality 
renders. Do use sliding!

 >  distance_maximum 0.0

Never mind this one, this is an obsolete parameter.

>  error_bound 0.4

Good value. No need to slide, normally.

 >  gray_threshold   0.5

Should be reduced as you increase recursion_limit.

>  low_error_factor 0.8

Do use an even lower value, e.g. 0.5, for high quality.

 >  minimum_reuse    0.015

Try lower values for top-quality renders, something like 0.005.

>  nearest_count    6

Another good candidate for sliding. Push it as high as 10.

 >  recursion_limit  1

I'd suggest using 2 or even 3 for top-quality. Slide.

Other radiosity settings you'll want to adjust:

   pretrace_start 0.064
   pretrace_end   0.002

You'll especially want to slide the latter; it should be a multiple-of-2 
fraction of pretrace_start. Use something like pretrace_end 0.032 for 
low-quality.

   always_sample off

You'll always want this off, as the default setting slows down the 
render /and/ leads to artifacts.

   normal on

If your textures use "normal {...}" statements, you want this on for 
high-quality renders.


Note that radiosity settings tend to be rather "tweaky"; if you 
encounter artifacts, toy around with the settings. Do so for each 
quality level you define: The parameters do interact quite significantly.

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Alain schrieb:
> Controls the pretrace passes. can be used to reduce some artefacts. The 
> value is a ratio of the horizontal dimention of the image been rendered.
> There is no point to set pretrace_end to anything lower than 
> 2/image_width meaning a last pretrace step of 2x2 pixels tiles.

Well, there is: It further reduces the need for final-trace gathering of 
radiosity samples (which invariably lead to artifacts).

> Interior scenes ferquently need a value of 2 to 4. If the radiosity 
> evvect need to take into acount something behind a pane of glass, and 
> you do a single pass rendering, you need at least a value of 3, 2 levels 
> been used to get through the pane.

This is not so: The radiosity recursion level is /only/ increased by 
genuine "radiosity bounces".

Conversely, however, radiosity bounces /do/ affect the /general/ trace 
level, so a max_trace_level barely enough to reach through a pane of 
glass will not be enough for radiosity to "see" through it. (POV-Ray 3.6 
and earlier also added other troublesome issues in this context, leading 
to the infamous black-splotch artifacts.)

(Your statement was actually true for some older POV-Ray 3.7 betas, but 
this has been changed again.)

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>clipka wrote:
> Alain schrieb:

Thank you Alain and clipka, you guys are superb, very helpful explanations by
both of you.

ibrahim

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