Pinpointing the source of light in an HDRI

[DJ-Studd]

Hi Guys,
first post as a VRay Advanced user .

Is there some kind of setting you can enable in Max/Viz to display where the primary source of light is coming from when using a HDRI? Or infact any other easy methods to see this?

Cheers
-- DJ

[DaForce]

no there is nothing in max/viz that can show you that. Its not really possible as such. I guess you could make a program that could make a best guess off the pixel values and track down the brights area or something.

You could try making a JPG version of the HDR and mapping it to a sphere then change the mapping to spherical environment and that way you shoule be able to see where the light source would be?!?!?!
Not sure just an idea... havnt tried it.. hehe

Hopefully someone else will have a better solution

[powerandrubber]

You could load the hdri in hdrishop and lower the exposure until the brightest spot is the only thing visible. Once you've identified that you can render a chrome ball in the top viewport and locate the spot in your 3dsmax environment. And/or hunt for it in a perspective viewport,

[chicoone]

Maybe some useful info on that subject:
LightGen Plugin for HDRShop
http://gl.ict.usc.edu/HDRShop/

LightGen importer for Max
http://www.cgtechniques.com/goodies/lightgen/

More on the same
http://gl.ict.usc.edu/HDRShop/

[olitech]

-or- if your HDR is loaded into the max enviro slot, go to Views>Viewport background>Use Environment Background>Display Background...then you'll be able to see your HDR in the viewport

[RErender]

Render a top down of a 1x1 box (at right angle to the scene) on a plane note the prevalent shadow in the scene. Measure the angle of the shadow compared to the adjacent side of the box, this will give the location on the xy plane. Then measure the distance from a corner of the box at the base of the shadow to the top of the shadow, solve for A using Pythagorean's theorem, this will give you the angle of incidence from the xy plane. Now simply construct a line from the same corner to the previous xy coordinate in the corresponding angle.

Heheh, just kidding

I like the olitech's viewport background idea.

[olitech]

OMG! Rerender...
i thought you were serious! lol...you forgot about sacrificing a rooster on the full moon while jumping on one foot.

The viewport trick does the trick...to line up your sun, just isolate your direct light and manually guide it to line up with the sunspot in the HDR.

Pythagoean's theorem......classic! :P

[DaForce]

ah cool.. didnt know you could show HDR's in viewport.. that that was limited to 8bit type image formats... well then yeah that is the better option

[olitech]

ah cool.. didnt know you could show HDR's in viewport.. that that was limited to 8bit type image formats... well then yeah that is the better option

Absolutely can....and if you reduce output amount (using max regular bitmap loader) you can actually see where the sun is

[DaForce]

Nice ... although having it mapped to a big ass sphere is probably easier in terms of aligning your light but your viewport way is easier and faster to setup.

[olitech]

"Easier"...that must be the best word in the world...

[DaForce]

I would say so

[DJ-Studd]

Thanks heaps guys,
this gives me a lot to go off. Now to find a rooster....

Is there a hotkey or some command to force a refresh of the viewport? Every time you move the camera, you have to tick and untick the "Show Background", otherwise the HDRI background doesn't update.

Hooroo!
-- DJ

[DaForce]

by default i think its 5 which redraws all views.. there is probabaly a more approriate one but that may work.
Unless of course you have changed that key to be something else.

[RErender]

Also works to scrub the timeline