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"Bald Eagle" <cre### [at] netscape net> wrote:
> I'm sure everyone has seen this at some point:
>
> When you look at a light source's reflection on a smooth piece of glass
> or metal or plastic, the scratches all tend to appear as a series of
> arcs and lines roughly in a circular pattern centered around the "hotspot".
>
Sometimes, spider webs look like that too. Which gave me the idea to do someting
similar to the twigs code already posted. Mine conists of just a bunch of
cylinders randomly arranged, with a 'moon' reflected in them. But the cylinders
aren't round, they're more like a flat oval shape-- to present more of a surface
for the moon to reflect off of. (I'm using reflection rather than phong or
specular.) It's not very good, but works. The reflections are VERY 'thin' and
noisy, due to the extreme angle of incidence with the moon.
Here, the light source itself doesn't really produce the 'tunnel' effect, it's
mostly the moon reflection. I also used max_trace_level of only 2, to try and
keep secondary reflections to a minimum.
-----
global_settings {assumed_gamma 1.0 max_trace_level 2}
camera {
perspective
location <1.5, 1.5, -4>
look_at <1.5, 1.5, 0>
right x*image_width/image_height
angle 67
}
light_source {
0*x
color rgb 20
looks_like{sphere{0,7 pigment{rgb 1} finish{ambient 10
emission 0 diffuse 0}}}
translate <15, 20, 100>
}
background{rgb 0}
#declare S = seed(13);
#declare STRAND =
cylinder{-10*x,10*x, 0.008 scale <1,1,15>
texture{
pigment{rgb 0.03}
finish{ambient 0.09 diffuse 0.05 reflection {0.0,0.6}}
/*
normal{
gradient x // try z too
scale .001
sine_wave
bump_size .5
}
*/
}
}
union{
#for(i,1,150)
object{STRAND
rotate 720*rand(S)*z
translate <-4 + 8*rand(S), -3 + 6*rand(S), 1 + 2*rand(S)>
}
#end
}
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This scene comes close to the initial examples given. I still have
trouble to get the reflection of the light to be broader to right and left.
//start code
#version 3.8;
global_settings {
assumed_gamma 1.0
}
camera {
location <0, 100, -100>
look_at <0, 0, 100>
direction z
right x*image_width/image_height
angle 54
}
light_source {
<0,0,0>
color rgb <1, 1, 1>*1
translate <0, 50, 100>*100
}
sky_sphere {
pigment {
gradient y
color_map {[0 rgb 1] [.5 rgb <0,0.3,1>]}
}
}
#local N_scratch =
normal {
bump_map {png "scratches.png" gamma 1}
rotate 90*x
}
plane {
y, 0
pigment {rgb 0.3}
normal {
average
normal_map {
[1.0 N_scratch scale 50 bump_size -1]
[1.0 N_scratch scale 40 bump_size -0.8]
[1.0 N_scratch scale 30 bump_size -0.6]
[1.0 N_scratch scale 20 bump_size -0.4]
[1.0 N_scratch scale 10 bump_size -0.2]
}
}
finish {
specular albedo 0.1
diffuse albedo 0.9
roughness 0.001
metallic
reflection {0.5, 1.0 metallic}
conserve_energy
}
}
//end code
--
Thomas
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On 25-1-2019 9:51, Thomas de Groot wrote:
> This scene comes close to the initial examples given. I still have
> trouble to get the reflection of the light to be broader to right and left.
>
Well, that last one is simple: change the finish roughness to a higher
value, e.g. 0.005 .
Also, build a pseudo orthographic scene:
camera {
location <0, 100, 0>
look_at <0, 0, 0>
direction z
right x*image_width/image_height
angle 54
}
light_source {
<0,0,0>
color rgb <1, 1, 1>*1
translate <0, 500, 0>
}
--
Thomas
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The latest variant, as shown in p.b.i, using the same scratch image_map,
results from the following code:
//start code
#version 3.8;
global_settings {
assumed_gamma 1.0
radiosity {
pretrace_start 0.08
pretrace_end 0.004
count 50, 1000
nearest_count 10, 5
error_bound 1
recursion_limit 1
low_error_factor .3
gray_threshold 0.0
minimum_reuse 0.015
maximum_reuse 0.1
brightness 1
adc_bailout 0.01/2
normal on
media off
always_sample off
//max_sample 1.0
}
}
camera {
location <0, 100, 0>
look_at <0, 0, 0>
direction z
right x*image_width/image_height
angle 54
}
light_source {
<0,0,0>
color rgb <1, 1, 1>*1
translate <0, 10e6, 0>
}
sky_sphere {
pigment {
gradient y
color_map {
[0.0 rgb <0.6,0.7,1.0>*0.7]
[0.7 rgb <0.0,0.1,0.8>*0.7]
}
}
}
#local N_scratch =
normal {
bump_map {png "scratches.png" gamma 1}
rotate 90*x
}
#local Strength = -1;
plane {
y, 0
material {
texture {
pigment {srgb <1.00, 0.62, 0.28>}
finish {
diffuse albedo 0.01
brilliance 1
specular albedo 0.7
roughness 0.00001
metallic on
fresnel on
reflection {0.0, 0.9 metallic on fresnel on}
conserve_energy
}
}
interior {
ior 1.5
}
}
material {
texture {
pigment {srgbt <1.00, 0.62, 0.28, 1>}
normal {
average
normal_map {
[1.0 N_scratch scale 50 rotate 30*y bump_size 1.0*Strength]
[0.5 N_scratch scale 40 rotate 60*y bump_size 0.8*Strength]
[0.4 N_scratch scale 30 rotate 90*y bump_size 0.6*Strength]
[0.3 N_scratch scale 20 rotate -90*y bump_size 0.4*Strength]
[0.2 N_scratch scale 10 rotate -60*y bump_size 0.2*Strength]
[0.1 N_scratch scale 1 rotate -30*y bump_size 0.1*Strength]
}
}
finish {
diffuse albedo 0.01
brilliance 1
specular albedo 0.1
roughness 0.001
metallic on
fresnel off
reflection {0.0, 0.9 metallic on fresnel on}
conserve_energy
}
}
interior {
ior 1.5
}
}
}
//end code
--
Thomas
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Note: To be entirely orthodox, the specular and reflection values should
be identical. So, in the lower of the layered materials given above set
them to e.g. 0.5, and in the upper material to e.g. 0.7
--
Thomas
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"Bald Eagle" <cre### [at] netscapenet> wrote:
> I'm sure everyone has seen this at some point:
>
> When you look at a light source's reflection on a smooth piece of glass or metal
> or plastic, the scratches all tend to appear as a series of arcs and lines
> roughly in a circular pattern centered around the "hotspot".
>
> I was wondering if anyone has ever attempted to replicate this effect, and
> perhaps has an optical explanation for why the scratches appear in a circular
> pattern.
This effect is the base for "scratch holograms"!! Have a look at
http://amasci.com/amateur/holohint.html
igmar
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On 16-5-2019 9:19, IGM wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
>> I'm sure everyone has seen this at some point:
>>
>> When you look at a light source's reflection on a smooth piece of glass or metal
>> or plastic, the scratches all tend to appear as a series of arcs and lines
>> roughly in a circular pattern centered around the "hotspot".
>>
>> I was wondering if anyone has ever attempted to replicate this effect, and
>> perhaps has an optical explanation for why the scratches appear in a circular
>> pattern.
>
>
> This effect is the base for "scratch holograms"!! Have a look at
> http://amasci.com/amateur/holohint.html
>
> igmar
>
>
>
LOL This is brilliant!
--
Thomas
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