[Radiance-general] rendering with environment maps

[Thomas Bleicher]

Hi

Sorry for replying late. I didn't have time for email yesterday.

1) Perhaps your use of the "glow" material for the environment box stops
the direct calculation from reaching the light source? Can you post the
definition of your light source? I know a combination of HDR mapped to a
sky dome and other light sources can be done but I'm not sure if this works
with a box, too.

2a) You can render the image of the environment map on the reflecting
sphere separately from the main scene and then just combine the two images.
You won't have the lighting pattern on the mirrored object, though. Perhaps
there is a way to capture the lighting pattern with a lambertian material
and multiply the values from both images? You'd have to make sure that your
environment texture captures accurate lighting data.

2b) Instead of reflecting a texture in the mirror ball you could just apply
the texture directly to the mirror. What real-world physical effect do you
want to simulate?

On Tue, Jul 21, 2015 at 12:24 PM, Minjung Kim <mkim85 at gmail.com> wrote:

> Thanks so much for your help, Thomas! That did the trick.
>
> I have two follow-up questions:
>
> (1) When I set the environment map, I also tried including an additional
> direct light source. Shouldn't the direct source have illuminated the
> Lambertian sphere? I tried setting the intensity of the direct source to be
> very high and the environment map to be low, just in case the environment
> map was washing out the influence of the direct source -- but still, the
> Lambertian sphere rendered completely black. Is it not possible to combine
> the environment map with additional light sources?
>
> (2) I want the lighting to be from an environment map, but there to be
> additional "environment" that the specular object reflects. More precisely,
> I want the specular object to be reflecting a world defined by a texture
> pattern, but using the lighting pattern from an environment map. Does that
> make sense?
>
> Regards,
>
> MJ
>
>
>
>
> On Mon, Jul 20, 2015 at 11:16 PM, Thomas Bleicher <tbleicher at gmail.com>
> wrote:
>
>> You need to throw in an "-ab 1" (or higher) in the rvu line. The HDR
>> image does not count as light source and so does not "illuminate" objects
>> with the default of "-ab 0". If you had more geometry in the scene you
>> would notice that everything is dark. The only thing you see is the HDR
>> image itself in direct view or reflected in the sphere (reflection is
>> calculated independently of the light distribution).
>>
>> Regards,
>> Thomas
>>
>>
>>
>> On Mon, Jul 20, 2015 at 8:41 PM, Minjung Kim <mkim85 at gmail.com> wrote:
>>
>>> Hi there,
>>>
>>> I have a question about rendering with environment maps. I set up a
>>> scene consisting of two spheres, one completely specular and one
>>> Lambertian, lit it with one of Paul Debevec's light probes (
>>> http://www.pauldebevec.com/Probes/). The specular sphere is rendering
>>> fine, but the Lambertian one is turning up completely black, and I have no
>>> idea why.
>>>
>>> My code looks like this:
>>>
>>> # make environment map
>>> void colorpict uff
>>> 9 red green blue uffizi_probe.hdr angmap.cal sb_u sb_v -rx 90
>>> 0 0
>>>
>>> uff glow uff_glow
>>> 0 0 4 1 1 1 0
>>>
>>> !genbox uff_glow boxenv 100 100 100 -i | xform -t -50 -50 -50
>>>
>>> # make materials
>>> void plastic spec # specular
>>> 0 0 5 .5 .5 .5 1.000000 0.000000
>>>
>>> void plastic lamb # Lambertian
>>> 0 0 5 1 1 1 0.0 0.0
>>>
>>> # make spheres
>>> spec sphere sph1 # specular
>>> 0 0 4 -.5000000 0.000000 0.000000 0.300000
>>>
>>> lamb sphere sph2 # Lambertian
>>> 0 0 4  .5000000 0.000000 0.000000 0.300000
>>>
>>> I then ran it like this:
>>>
>>> oconv scene.rad > scene.oct
>>> rvu -vtv -vv 10 -vh 10 -vp 0 -10 0 scene.oct
>>>
>>> When I do this, I get a mirrored sphere and a completely black sphere.
>>> To make sure that the problem wasn't with my code, I downloaded this sample
>>> code from Debevec's website (http://www.pauldebevec.com/RNL/Source/).
>>> When I changed the materials in the .rad file to be Lambertian (lines
>>> 182-190 in rnl_scene.rad), the objects rendered as completely black.
>>>
>>> Has anybody ever run into this problem before? I am using RADIANCE 4.2,
>>> on OS X 10.7 (home) and OS X 10.9 (work).
>>>
>>> Regards,
>>>
>>> MJ
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
>>> Radiance-general at radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>>
>>
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