What is TONE MAPPING and WHITE POINT

FauvistFauvist Posts: 1,029

I keep hearing it mentioned, but there seems to be tone mapping and white point meanings that are different than the ones for 3D renders.  Does anyone have an easy explaination for the 3D meaning?

Thanks!

Comments

  • grinch2901grinch2901 Posts: 1,175

    I use the white point to correct for color in an image I don't want. For example some of my HDRI leave a yellow or orange hue to the image. If I set the white point to a similar yellow (or orange as the case may be) it tells the renderer to shift it's perception of color such that the yellow shade will be considered white and essentially it removes that shade from the image. Basically it gets rid of the tint I don't want. I don't know if I'm really using it right but I think that's more or less what it's doing in real life too.  You calibrate your camera to some object that is to be considered the reference white and it adjusts the colors accordingly except in a camera it's called "white balance".

    But I'm not a photographer or a particularly good 3D artist so you may want to seek other opinions!

  • nemesis10nemesis10 Posts: 1,479
    Fauvist said:

    I keep hearing it mentioned, but there seems to be tone mapping and white point meanings that are different than the ones for 3D renders.  Does anyone have an easy explaination for the 3D meaning?

    Thanks!

    Imagine that you are watching a black and white movie.... there is a value for the darkest color, the brightest point (the white point) and the 50% grey.... when you adjust those, you are adjusting contrast.... So in a 3d scene, you rendere a scene as bright as you can while retaining the detail, choose the brightest value you want (the white point), choose the dark est you want, and then adjust the midrange to make a room that is blindingly bright or a gloomy near midnight or anything in between. That is one method of tone mapping as used in movies and tv where even night scenes are filled under very bright lights.  A second method is to render the scene under very bright conditions, very dark conditons, and something in between, and combine them using an image editor to create an hdr (high dynamic range) image where nothing is too bright or too dark.... I use Aurora https://aurorahdr.com to do this; the link will show some examples.  In iray, the HDRI backgrounds are the summation of a few images including bright bright sunlight, normal ambient light etc... so that they can act as light sources.

  • Joe WebbJoe Webb Posts: 786

    Tonal Rage is very very handy for this. And if you apply the presets and review the Tone Mapping in the Render Settings editor, you get an idea of how things work.

    Or you can just start messing with those settings. But I think the presets in that product are pretty good.

  • macleanmaclean Posts: 2,161

    Tone Mapping is probably the most essential (and misunderstood) control for Iray. I keep hearing ppl talk about ramping lights up to billions of lumens for interiors. This is completely unnecessary. If you set Tone Mapping to a value for the scene, you shouldn't need to add more power to the lights. Remember that the default value of 13.0 is for a bright cloudy day - not indoor scenes. You can find a guide to the values here.

    https://en.wikipedia.org/wiki/Exposure_value#Tabulated_exposure_values

    As Grinch said, white point is used to correct color bias in HDRIs. Set it to the color you want to get rid of to get a neutral white tone..

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