Infrared Houdini render

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Hi!

Is it possible to render images that look like infrared images with Houdini?
I don't know if it's possible and how to attack this problem. My first thought was to write a shader for every object (in my case, one for the ocean and one for a boat).

Had someone the same problem?

I hope someone with more experience can help me.

Thx
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I would just do it in post. You can easily accomplish that type of look in AfterEffects, and I assume Nuke and Fusion have similar Colorama-type of nodes.
>>Kays
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Infrared doesn't look that much different than a regular black and white image expect for objects that have very different absorption spectra than under visible light, such as green foliage. You can fake it by using just the red channel and using alternate textures for those objects that are extraordinarily reflective in infrared.



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Thanks for the replies!

I will try it with a python script.

However, many users said it's impossible to get an infrared image out of an rgp image.

Thanks!
Edited by MEder97 - Oct. 28, 2020 03:22:57
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depending on how “real” you want it to be you may need some attribute on your geo representing temperature and maybe a custom shader, or at least an AOV for that attribute as in reality the color of the pixel doesn't necessarily represent the temperature
for reflective surfaces like your ocean you may need to have separate pass (or within shader), rendering just reflected temperature based on fresnel combined with the temperature of the ocean for the rest or maybe some refracted ones also if there are some temperature differences within the body of water itself
Tomas Slancik
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tamte
depending on how “real” you want it to be you may need some attribute on your geo representing temperature and maybe a custom shader, or at least an AOV for that attribute as in reality the color of the pixel doesn't necessarily represent the temperature
for reflective surfaces like your ocean you may need to have separate pass (or within shader), rendering just reflected temperature based on fresnel combined with the temperature of the ocean for the rest or maybe some refracted ones also if there are some temperature differences within the body of water itself

why would the temperature matter? Water looks the same under infrared as it does visible, since it's just reflecting the environment, and dielectric reflection is not wavelength-dependent. The scattering and dispersion in the water might be a little different though, but not much. It will probably look slightly more clear as the water scatters longer wavelengths less.
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jsmack
why would the temperature matter? Water looks the same under infrared as it does visible, since it's just reflecting the environment, and dielectric reflection is not wavelength-dependent. The scattering and dispersion in the water might be a little different though, but not much. It will probably look slightly more clear as the water scatters longer wavelengths less.

well, infra light is not visible, so the “temperature” attribute would represent those invisible wavelengths

if ocean reflects cold boat with a warm human body on the deck then you would see the difference, imagine both boat and human have the same color in visible spectrum otherwise or a lot more detail like textures, etc…. so even for direct rays the temperature and the visual texture can also differ a lot as a pattern on your sweater doesn't necessarily represent different temperature radiation
also lighting may not contribute to temperature change of a surface as much as to the visual color, or at all

so because we are dealing with different spectrum range you may need to account for that, obviously it doesn't have to be secial atttribute, you can just tweak material or use Cd directly to represent temperature
Edited by tamte - Oct. 28, 2020 17:49:15
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Thanks for all of your answers

jsmack
tamte
depending on how “real” you want it to be you may need some attribute on your geo representing temperature and maybe a custom shader, or at least an AOV for that attribute as in reality the color of the pixel doesn't necessarily represent the temperature
for reflective surfaces like your ocean you may need to have separate pass (or within shader), rendering just reflected temperature based on fresnel combined with the temperature of the ocean for the rest or maybe some refracted ones also if there are some temperature differences within the body of water itself


We need these images to train an object detector. It should be a good trade-off between realistic output and workload.

I will try to implement a python script and see how realistic the results look. I also got masks where the objects are. This will be much easier with this information.

Thanks for your opinion on this problem. I don't have much knowledge about shaders and Houdini.
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