Timeline for Spectral path tracing - image color/brightness incorrect
Current License: CC BY-SA 3.0
19 events
| when toggle format | what | by | license | comment | |
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| Mar 21, 2016 at 14:18 | answer | added | ivokabel | timeline score: 7 | |
| Mar 21, 2016 at 12:29 | comment | added | ivokabel | Let us continue this discussion in chat. | |
| Mar 21, 2016 at 10:13 | comment | added | Fabrizio Duroni | In fact if I multiply the material->le with a multiplier the scene become more bright. Here are some rendered images drive.google.com/drive/u/1/folders/0BxeVnHLvT8-7Ty1jTVM5U1JJdms. They are not totally correct (as I expect the floor to be white), but maybe i just need a higher multiplier. Do you see any error in code that could avoid this multiplier (some error in the pdf/BRDF calculation)? Thank you very much again @ivokabel. | |
| Mar 21, 2016 at 10:10 | comment | added | Fabrizio Duroni | This is an example scene generated with a different illuminant SPD and the Whitted model raw.githubusercontent.com/chicio/Spectrum-Clara-Lux-Tracer/… | |
| Mar 21, 2016 at 10:09 | comment | added | Fabrizio Duroni | @ivokabel scene->light->spectrum and material->le contain the same value, the D65 SPD. In the scene init I give to the material of light object the SPD of the scene light. My scenes supports only one light. The normalization in CIE1931XYZ::tristimulusValues() follows the standard conversion from spd to CIE XYZ that you can found here scratchapixel.com/old/lessons/3d-basic-lessons/… or on the wiki CIE XYZ page. Is this passage not correct? I don't think so because my engine supports also the whitted ray tracing model that seems to be ok. | |
| Mar 21, 2016 at 10:01 | comment | added | ivokabel |
After re-reading your code, it is unclear to me what is the relation between scene->light->spectrum and material->le in PathBRDF::shade. Is it the same value? If yes, do you allow just one light source in your scene? Moreover, why do you normalize your XYZ values with illuminant luminance in CIE1931XYZ::tristimulusValues()?
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| Mar 21, 2016 at 0:11 | comment | added | ivokabel | I might get to it tomorrow... | |
| Mar 21, 2016 at 0:05 | comment | added | Fabrizio Duroni | @ivokabel can you just write a response to my question? In this way your answer an the other (if someone else would response) will remain as reference, and the user will not have to search in the :) thank you. | |
| Mar 20, 2016 at 23:58 | comment | added | ivokabel | ...and sorry for the confusion about exposure. What I meant is the image value which maps onto maximum value in the resulting picture, 255 in your case. Don't worry about that at this point. | |
| Mar 20, 2016 at 23:58 | comment | added | Fabrizio Duroni | @ivokabel what about the render exposure value? Where do i take 1? | |
| Mar 20, 2016 at 23:55 | comment | added | ivokabel | Yes, multiplying the SPD of your illuminant with a value (whether constant or variable) during or before the ray tracing is the way to go. | |
| Mar 20, 2016 at 23:45 | comment | added | Fabrizio Duroni | Thank you @ivokabel for the suggestion about the parameter radiance. Could it be just a constant that will be multiplied with the spd of the illuminant during the tracing of rays? Or do i need to multiply the spd of the illuminant during the conversion from spd to cie xyz? Also I don't understand what you mean with renderer exposure value. Where do I take 1 as its value? | |
| Mar 20, 2016 at 23:37 | comment | added | ivokabel | If I am not mistaken, D65 only defines the shape of the spectrum, not the intensity. Therefore, you will really have to add a parameter telling the amount of emitting radiance, or something similar. Related topic is the renderer exposure value, but I saw that you take 1 as the limit value, so you don't have to bother with this one. | |
| Mar 20, 2016 at 23:21 | history | edited | Fabrizio Duroni | CC BY-SA 3.0 |
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| Mar 20, 2016 at 23:17 | comment | added | Fabrizio Duroni | @ivokabel Do i need to define a brightness paramter and use it somewhere? | |
| Mar 20, 2016 at 23:17 | comment | added | Fabrizio Duroni | @ivokabel but my materials should look white and light gray. The SPD of the illuminant used is the D65. Do i need to tweak the spd of the light in some way? | |
| Mar 20, 2016 at 23:14 | comment | added | ivokabel | It is perfectly OK if your material looks dark gray if you illuminate it with weak light source. What is the brightness of the light source? | |
| Mar 20, 2016 at 21:40 | history | edited | Fabrizio Duroni | CC BY-SA 3.0 |
added 28 characters in body
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| Mar 20, 2016 at 21:24 | history | asked | Fabrizio Duroni | CC BY-SA 3.0 |
