Danny nous apporta ses lumieres ainsi en ce 2004/05/18 15:08... :

>"Danny" <danzaetz> wrote:
>  
>
>>Alain <aze### [at] qwertygov> wrote:
>>    
>>
>>>Danny nous apporta ses lumieres ainsi en ce 2004/05/17 16:39... :
>>>
>>>      
>>>
>>>>Alain <aze### [at] qwertygov> wrote:
>>>>
>>>>
>>>>        
>>>>
>>>>>Danny nous apporta ses lumieres ainsi en ce 2004/05/17 05:23... :
>>>>>
>>>>>
>>>>>
>>>>>          
>>>>>
>>>>>>Alain <aze### [at] qwertygov> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>I used exactly what you told me, and I got a cylinder with white edges that
>>>>>>fades to nothing in the middle (without any red at all), and even those
>>>>>>white edges disappear as the cylinder continues on.  I'm using POV-Ray 3.5,
>>>>>>and here is the code I used:
>>>>>>
>>>>>>cylinder{<100,0,0>,<0,0,0>, .20
>>>>>>       texture {
>>>>>>  pigment { color rgbt 1}
>>>>>>  finish{reflection 0}}
>>>>>>     interior{media{emission rgb 1
>>>>>>     density{ cylindrical
>>>>>>     color_map{[0 rgb 0][0.5 rgb<1,0,0>][0.98 rgb 1][1 rgb 2]}
>>>>>>     }}}
>>>>>>     hollow
>>>>>>     translate<0,0,2>
>>>>>>     }
>>>>>>
>>>>>>Can you tell me what I'm doing wrong, and how to fix it?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>            
>>>>>>
>>>>>Set the radius of the cylinder to 1, then rescale it by scale<.2,1,.2>
>>>>>just before you rotate it.
>>>>>You don't need to set finish{reflection 0}}, it's the default value.
>>>>>Set your cylinder verticaly, as it's the orientation of the cylindrical
>>>>>pattern, then rotate the whole thing.
>>>>>...
>>>>>scale<0.2, 1, 0.2>
>>>>>rotate -90*z
>>>>>translate<0, 0, 2>
>>>>>}// that's the last brace
>>>>>
>>>>>Alain
>>>>>
>>>>>
>>>>>          
>>>>>
>>>>OK, now it looks good when I don't scale it, but scaling it seems to mess it
>>>>up.
>>>>When I scale it up it still seems to look OK, except the inner white part
>>>>has become enlarged disproportionately.  But when I scale it down, I lose
>>>>the white part completely, and all I have is a very dimly red cylinder.
>>>>Can you explain why it's doing this and how I can make it scale down right?
>>>>
>>>>
>>>>
>>>>        
>>>>
>>>Try lowering the 0.98 to a smaler value, thus enlarging the central
>>>part. As it is now, the white center part only have a radius of 0.02
>>>units and may disappears when scaled down or if the image is generated
>>>at a low resolution.
>>>Don't scale only the media but the whole cylinder containing the media.
>>>
>>>Alain
>>>      
>>>
>>Thanks a lot for all your help!  I managed to fix the scaling problem by
>>multiplying the brightness of all the color map values by 5.  I guess this
>>is because there is less matter in the media to show up if I scale it down
>>to a fifth of its size.
>>    
>>
Good guess

>>Thanks,
>>Danny
>>    
>>
>
>I've got another problem. For some strange reason, my media cylinder is
>acting like a convex lens. It's showing an narrowed image on the right side
>of the cylinder of an object behind and to the left of it.  It's refracting
>(not reflecting) light, I think.  When I zoom out, it looks like ugly white
>lines on the side of my laser. How do I get rid of them?
>
>Danny
>
>  
>
With emissive only media, the beam is effectively transparent, that is, 
you see anything that may be behind. That was (barely) visible in the 
small sample as a slight discontuity near the middle of the image. You 
may want to add some absorbtion and/or scattering, it's not realistic as 
the beam is only light, but may be more aestetic.

Alain

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