Hi all,

I'm finally getting to spend some time learning and creating with PovRay.
Although I am reading with great interest about the many advance techniques
available with PovRay, for now I'm trying to master the basic's 1st.

Attached is one of my original efforts that is 99% primative constructive
solid geometry. Floor pump hose which is a sphere_sweep is the only non
primative.
Calender from PovRay wiki at:   http://www.wikipov.org/ow.asp?MakeCalendar

Tandem picture on imaged mapped onto calendar is same CSG object in scene,
rendered on white background with colored lights and a slight warp normal
to camera to give a hand drawn look.

I think I need another light source from say a window, skylight, or door
opening, as when this scene is dark enough to have the mood I/m going for,
it's seems too dark, and when I lighten it up with the existing light, it
seems fake.

I'd like to improve my skills and do better in the next IRTC than my 1st
entry, based somewhat on this scene.  Let me know what you think . . .

Key lighting related settings are below:

.. . .

global_settings { assumed_gamma 2.50 max_trace_level 5
    ambient_light rgb<.0, .0, .0>   // Best set to zero if Radiosity used
    radiosity { pretrace_start 0.08 pretrace_end 0.05 count 90 nearest_count
7 error_bound 1.5 recursion_limit 4 low_error_factor .6
                gray_threshold 0.5  minimum_reuse 0.013 brightness 1
adc_bailout 0.01 normal on always_sample off}
// end global settings

.. . .

#declare Dist=160; // 220;
light_source { <0,0,0>// position (translated below)
  color rgb <1,1,1>   // White light
  area_light          // slow but soft-better shadows results
  <1, 0, 0> <0, 0, 1> // lights spread out across this distance (x * z)
  6, 6                // total number of lights in grid (4x*4z = 16 lights)
  adaptive 0          // 0,1,2,3...
  jitter              // adds random softening of light
  circular            // make the shape of the light circular
  orient              // orient light
  translate <lx, ly+1 , lz>  // <x y z> position of light - match to light
fixture in scene
}
// Added lights to make scene's light fixture look more like a source of
illumination
light_source { <lx, ly+1, lz> color Gray20 fade_distance Dist fade_power 2
shadowless }
light_source { <lx, ly+1, lz> color White fade_distance Dist fade_power 2 }
// shadowless}
light_source { <lx, ly+1, lz> color Yellow fade_distance Dist fade_power 2 }
//shadowless}
light_source { <lx-2,ly-12,lz+2> color rgb < .1,0,0> fade_distance Dist
fade_power 2 shadowless }  // Brighten up light fixture pull crystal

.. . .

Comments and suggestings welcome,

M. Cv

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Attachments:
Download 'tandem_in_shed_m.jpg' (341 KB)

Preview of image 'tandem_in_shed_m.jpg'

Warning: Remarks/comments ahead.

Looks good for nighttime, to me; even if a garage door were open, if no 
nearby streetlight exists.

It shouldn't appear to be a point source, though. That area_light isn't wide 
enough, if it equaled the width of that bulb there would be softer shadow 
lines. And it ought to diffuse light from the shade, too, so it could need a 
second wider area_light for that. The pull chain's shadow would never be 
sharp. The use of so many lights might be overkill; especially the dim red 
one since you could probably change the pull chain texture (ambient or 
diffuse or ???) instead of applying a light source. But I'm not sure of what 
you were really trying with that.

Also, I could be mistaken, I think 'circular' gets cancelled out when using 
'orient' in area lights.

I like the big black ants marching across the floor. Maybe needs a large 
crumb or partially eaten donut (thinking torus here) dropped on the floor 
for them to be trekking toward.

Observation about the calendar: would be better to make it a bezier_patch 
with the image uv mapped onto it, that way it can have some curl to the 
paper.

Anyway, to my eyes and mind, the room has the right feel. I wouldn't want to 
add a window with a sunlit scene outdoors. To do so would get interesting, 
though, because then you'd be attempting to balance the appearance of a 
darkened room with daylight shining in [sarcasm] and that can be fun 
[/sarcasm].  ;)

Bob Hughes

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3D_Fusion wrote:
> Hi all,
> 
> I'm finally getting to spend some time learning and creating with PovRay.
> Although I am reading with great interest about the many advance techniques
> available with PovRay, for now I'm trying to master the basic's 1st.
> 
> Attached is one of my original efforts that is 99% primative constructive
> solid geometry. Floor pump hose which is a sphere_sweep is the only non
> primative.
> Calender from PovRay wiki at:   http://www.wikipov.org/ow.asp?MakeCalendar
> 
> Tandem picture on imaged mapped onto calendar is same CSG object in scene,
> rendered on white background with colored lights and a slight warp normal
> to camera to give a hand drawn look.
> 
> I think I need another light source from say a window, skylight, or door
> opening, as when this scene is dark enough to have the mood I/m going for,
> it's seems too dark, and when I lighten it up with the existing light, it
> seems fake.
> 
> I'd like to improve my skills and do better in the next IRTC than my 1st
> entry, based somewhat on this scene.  Let me know what you think . . .
> 
> Key lighting related settings are below:
> 
> .. . .
> 
> global_settings { assumed_gamma 2.50 max_trace_level 5
>     ambient_light rgb<.0, .0, .0>   // Best set to zero if Radiosity used
>     radiosity { pretrace_start 0.08 pretrace_end 0.05 count 90 nearest_count
> 7 error_bound 1.5 recursion_limit 4 low_error_factor .6
>                 gray_threshold 0.5  minimum_reuse 0.013 brightness 1
> adc_bailout 0.01 normal on always_sample off}
> // end global settings
> 
> .. . .
> 
> #declare Dist=160; // 220;
> light_source { <0,0,0>// position (translated below)
>   color rgb <1,1,1>   // White light
>   area_light          // slow but soft-better shadows results
>   <1, 0, 0> <0, 0, 1> // lights spread out across this distance (x * z)
>   6, 6                // total number of lights in grid (4x*4z = 16 lights)
>   adaptive 0          // 0,1,2,3...
>   jitter              // adds random softening of light
>   circular            // make the shape of the light circular
>   orient              // orient light
>   translate <lx, ly+1 , lz>  // <x y z> position of light - match to light
> fixture in scene
> }
> // Added lights to make scene's light fixture look more like a source of
> illumination
> light_source { <lx, ly+1, lz> color Gray20 fade_distance Dist fade_power 2
> shadowless }
> light_source { <lx, ly+1, lz> color White fade_distance Dist fade_power 2 }
> // shadowless}
> light_source { <lx, ly+1, lz> color Yellow fade_distance Dist fade_power 2 }
> //shadowless}
> light_source { <lx-2,ly-12,lz+2> color rgb < .1,0,0> fade_distance Dist
> fade_power 2 shadowless }  // Brighten up light fixture pull crystal
> 
> .. . .
> 
> Comments and suggestings welcome,
> 
> M. Cv
> 
> 
> ------------------------------------------------------------------------
> 
is it me or are the chainwheels different sizes ?

stephen

Post a reply to this message

3D_Fusion wrote:
> I think I need another light source from say a window, skylight, or door
> opening, as when this scene is dark enough to have the mood I/m going for,
> it's seems too dark, and when I lighten it up with the existing light, it
> seems fake.

I think that adding radiosity would probably make the lighting look 
better. Lighter, without adding a "fake" light source.

/ martin

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stephen parkinson nous apporta ses lumieres en ce 2005-06-16 23:18:

>>
>> ------------------------------------------------------------------------
>>
> is it me or are the chainwheels different sizes ?
> 
> stephen
To Stephen:
On modern tandem, there are 2 chains. The first runs between the 2 pedaliers, It use
smaller gears. 
The second one runs from the back pedalier to the rear wheel and use a larger gear.
Those chains are 
also on oposite sides, the front one been on the left side. This is to let you have a
front deraileur.

To 3D_Fusion:
You may want to tweak your radiosity settings.
ambient_light in global_settings multiply any ambient value used, set to zero, it
prevent you from 
using any high ambient object as light source. Better to set #default{finish{ambient
0}}
Setting pretrace_end to a lower value may give some improvement, try 0.02 or 0.01 (use
the 
pretrace_start value divided by a power of 2 for _end as POV Ray divide the tiles size
by 2 for each 
step)
Increasing brightness to a little over 1 will brighten the whole scene.
assumed_gamma 2.50 darken the scene, try reducing this value closer to 1.
If you don't use normals in the scene, you should set normal off, it will save you
some render time.
The 3 auxiliary lights can be replaced by one having the following colour: rgb<2.2,
2.2, 1.2> adding 
all 3 in one. This will accelerate the rendering speen by reducing the number of
lights.
In fact, I'd replace the main light and the 3 auxiliary ones by 1 much stronger one.
Keep the 
area_light, but add fade_distance dist and fade_power 1.8. Set it's colour to
something like 
rgb<120,120,100> fade_distance 1 (the extent of the area_light) fade_power 2
You can use a larger value for the area_light aray, 17*17 is a good choice, very
smooth results, not 
much longer using adaptive 0. I'd use adaptive 1, or use no_shadow on the pull chain,
now your pull 
chain will cast 2 shadows, unless that's what you want.  (small object close to the
area_light)

Alain

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Thanks for all the ideas.

Now to get busy and apply many of the suggestions to improve this image's
lighting and also learn how to do better on future PovRay renders using
your combined insights.

Thanks much to those who took the time to posted comments and suggestions,

M. Cv

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