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Nano Particle avatar image
Nano Particle asked ·

Physical sky map horizon line adjustment,Physical sky horizon line 3dsMax

Hello,

I have linked an Arnold distant light to a legacy Mental Ray sun system in order to control the lighting direction by geographic location, date and time. (MR sunlight and skylight are turned off).

I have set my exposure control to be by "physical camera" but I have disabled the "use physical camera controls if available". I have set the exposure to 13.0EV.

I brought the Arnold Physical Sky Environment map into the material browser and unticked 'Enable Sun" ( I do not want to have to control the sun position using Azimuth and Elevation).

I have then dragged that map into the background environment slot and ticked 'use map'.

This set up allows me to control the light direction using the MR date time system but I also have a sky in the background.

HOWEVER, below the horizon line, where no objects are present the scene, it renders black unless the camera and its target are at the same height and / or there is a ridiculously large plane at the base to cover up the black. I would like to either adjust the horizon line to suit the camera position or at least make these black areas render white instead of black!!!!!

Any suggestions welcome.

,

Shifting the black line of the horizon

lightphysically based
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Mads Drøschler avatar image
Mads Drøschler answered ·

Since the environment does not have hooks to any uvw manipulations, you can take the spherical camera, set render resolution to what you want, render out the environment map at the settings you want.
Install it on an OSL bitmap look up node, and use an UV Transform node to offset the map, with an environment mapping node controling general layout.
It takes less than a second to render a new environment map that can get autoloaded and recalled in a master scene, so its very fast to update, if you want to adjust things, or store different variants for seperate shots.

I included a sun in this, hard light and complete control over vertical offset.

https://i.imgur.com/VARIOGg.gif

So, and when you sit and look dev, account for the changing sun if you got any at any point in some other project, you can see that when I offset to lower the horizon, the sun actually also ducks, vissible in gif. So just place your sun higher so it comes down to your wanted place after the offset is introduced ~

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Nano Particle avatar image
Nano Particle answered ·

Dear Mads,

Thank you for your reply and great gif ! (though I think I need it at about 1/4 speed:)). It is a bit to wrap my head around but I will have a go, I've not used the OSL shaders yet...... In the gif it looks like there are two shadows? One is very pale (may just be a reflection?)

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must be reflections, only 1 sun in the environment map.

Tell me, which version of max are you using? I can surply some training material and a slower video going over it, if you want.

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Went ahead and did a video from scratch.
Video

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huge thank you for the video Mads, what a work around! As you mention in your comment above, the sun dips with the change in the horizon line offset. I was hoping to control the sun position (and shadows) using the legacy MR daylight system. Do you think if I follow your workflow but before rendering out the spherical camera I uncheck the 'Enable Sun', I might be able to just have an Arnold P.Sky (with adjustable horizon) which I apply to the environment slot, then in the scene I could use the MR daylight system linked to a distant light to fake a sun? Then somehow link Sky to MR daylight?

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That'll work just fine.
I included the sun, but yes it's just a tick in the shader to remove it.
As you mention if you remove it, you can use the linked direct lamp to dictate the hard shadows live.

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