Uniform sky

Hi Radiance experts,
I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or -c
option can give me a uniform cloudy sky and maybe give me the ground truth
values. I tried both of them but always get 'no lighting source warning'
and a very dark scene when I try to use rpict and pfilt on the .oct
generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

Hi, Vera, may I ask what you mean by "ground truth pixel value"?

- JS

Vera Liu <[email protected]>于2014年5月5日星期一写道:

···

Hi Radiance experts,
I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or -c
option can give me a uniform cloudy sky and maybe give me the ground truth
values. I tried both of them but always get 'no lighting source warning'
and a very dark scene when I try to use rpict and pfilt on the .oct
generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

Hi Joe,
For the ground truth I'm thinking about just the surface lit by the light
at each pixel without any ray tracing. Basically, the RGB of the surface as
it would be if it were directly lit by the light without any
interreflections or specularities. I figured that a uniform sky would do
the trick.

Best,
Vera

···

On Sun, May 4, 2014 at 7:08 PM, Joe Smith <[email protected]> wrote:

Hi, Vera, may I ask what you mean by "ground truth pixel value"?

- JS

Vera Liu <[email protected]>于2014年5月5日星期一写道:

Hi Radiance experts,

I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or -c
option can give me a uniform cloudy sky and maybe give me the ground truth
values. I tried both of them but always get 'no lighting source warning'
and a very dark scene when I try to use rpict and pfilt on the .oct
generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Vera,

I am not sure this will work, but I would tune a gray "Ambient Value"
instead of using a Uniform Sky.

Try something like

"rpict -ab 0 -av 1 1 1 octree_without_light_sources"

A "pi" (3.1415) might be needed somewhere. But I think this is the way to
go instead of using a uniform sky.

Bye!

···

2014-05-04 22:50 GMT-04:00 Vera Liu <[email protected]>:

Hi Joe,
For the ground truth I'm thinking about just the surface lit by the light
at each pixel without any ray tracing. Basically, the RGB of the surface as
it would be if it were directly lit by the light without any
interreflections or specularities. I figured that a uniform sky would do
the trick.

Best,
Vera

On Sun, May 4, 2014 at 7:08 PM, Joe Smith <[email protected]>wrote:

Hi, Vera, may I ask what you mean by "ground truth pixel value"?

- JS

Vera Liu <[email protected]>于2014年5月5日星期一写道:

Hi Radiance experts,

I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or -c
option can give me a uniform cloudy sky and maybe give me the ground truth
values. I tried both of them but always get 'no lighting source warning'
and a very dark scene when I try to use rpict and pfilt on the .oct
generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

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Vera

This sounds like you are trying to create something like an "ambient
occlusion" or "clay rendering"; the closer you are to an object the more
obstructed the view of the sky is and so the ground gets darker.

You can indeed create this using a uniform sky but you have to use "-ab 1"
for your rendering or the sky will not contribute to the scene. The "no
light sources found" warning comes up because a "glow" material that is
used for the sky technically does not count as a light "source" Radiance.

If you plan to use the rendering for analysis you can set the sky
brightness to a known quantity so that the rendering can be interpreted as
an absolute value of the obstruction of the sky. I think John Mardaljevic
wrote down the math for this in the Rendering with Radiance chapter on
skies/daylight. You should also add "-av 0 0 0" or the added ambient value
will skew your results.

Regards,
Thomas

···

On Sun, May 4, 2014 at 9:50 PM, Vera Liu <[email protected]> wrote:

Hi Joe,
For the ground truth I'm thinking about just the surface lit by the light
at each pixel without any ray tracing. Basically, the RGB of the surface as
it would be if it were directly lit by the light without any
interreflections or specularities. I figured that a uniform sky would do
the trick.

Best,
Vera

On Sun, May 4, 2014 at 7:08 PM, Joe Smith <[email protected]>wrote:

Hi, Vera, may I ask what you mean by "ground truth pixel value"?

- JS

Vera Liu <[email protected]>于2014年5月5日星期一写道:

Hi Radiance experts,

I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or -c
option can give me a uniform cloudy sky and maybe give me the ground truth
values. I tried both of them but always get 'no lighting source warning'
and a very dark scene when I try to use rpict and pfilt on the .oct
generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Thank you all for the replies! I got it working now. I can see that -ab set
to zero indicates no indirect calculation so I think this should give me
the ground truth values. Thank you all very much.

Best,
Vera

···

On Mon, May 5, 2014 at 7:02 AM, Thomas Bleicher <[email protected]> wrote:

Vera

This sounds like you are trying to create something like an "ambient
occlusion" or "clay rendering"; the closer you are to an object the more
obstructed the view of the sky is and so the ground gets darker.

You can indeed create this using a uniform sky but you have to use "-ab 1"
for your rendering or the sky will not contribute to the scene. The "no
light sources found" warning comes up because a "glow" material that is
used for the sky technically does not count as a light "source" Radiance.

If you plan to use the rendering for analysis you can set the sky
brightness to a known quantity so that the rendering can be interpreted as
an absolute value of the obstruction of the sky. I think John Mardaljevic
wrote down the math for this in the Rendering with Radiance chapter on
skies/daylight. You should also add "-av 0 0 0" or the added ambient value
will skew your results.

Regards,
Thomas

On Sun, May 4, 2014 at 9:50 PM, Vera Liu <[email protected]> wrote:

Hi Joe,
For the ground truth I'm thinking about just the surface lit by the light
at each pixel without any ray tracing. Basically, the RGB of the surface as
it would be if it were directly lit by the light without any
interreflections or specularities. I figured that a uniform sky would do
the trick.

Best,
Vera

On Sun, May 4, 2014 at 7:08 PM, Joe Smith <[email protected]>wrote:

Hi, Vera, may I ask what you mean by "ground truth pixel value"?

- JS

Vera Liu <[email protected]>于2014年5月5日星期一写道:

Hi Radiance experts,

I want to get the ground truth pixel values of a scene generated by
radiance and I figured the best way is to use a uniform sky where the sky
it's 1,1,1...everywhere. The way I'm currently using is by specifying a sun
!gensky 4 1 12 +s -a 40 -o 98 -m 105
skyfunc glow sky_glow
0
0
4 1 1 1 0
sky_glow source sky
0
0
4 0 0 1 180

This results in shadows in the final scene. I found that -u option or
-c option can give me a uniform cloudy sky and maybe give me the ground
truth values. I tried both of them but always get 'no lighting source
warning' and a very dark scene when I try to use rpict and pfilt on the
.oct generated. I think I might be understanding something wrong. Could you
please give me a hint on this? The two options I tried are:
!gensky 3 20 12 -a 40 -o 98 -m 105 -u -B 100
and
!gensky -ang 45 0 -c -b 1

Thank you very much!
Best,
Vera

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general