Iray Spotlights vs Mesh Lights

tl155180

Hi All,

I'm back from my Fallout 4 binge with questions about the different lighting methods in Iray.

I've noticed that photometric spotlights seem to produce a lot more specular light and slightly more colour depth than something like a plane primitive mesh light, which produces softer, more realistic shadows. However, I often find that lighting a scene with spotlights looks less realistic. Does anyone know how to increase the specular effect of a mesh light?

Edit: Or maybe its more a matter of light dispersal than specular. Maybe because the light is more forward-focused in a spotlight it highlights the specular areas more...

Thanks!

peteVault

My only advice is to decrease the area of the mesh light. The smaller the mesh, the sharper the shadow....perhaps through experimentation, you can find a compromise between the mesh and photometric light.

evilded777

Its a combination of things.

 

I recommend spotlights for lighting figures, meshlights for environmental lighting or background lighting.

You have a great deal of control over the spotlight.  Try increasing the size of the "mesh", or widening the Spread Angle. Unless you have an IES profile on your meshlight, you are getting basically 180 degrees of light projection, where as a spotlight's default is in a 60 degree arc.  That's one of the big differences as to why the lights function differently.  180 degrees is not particularly efficient.

Oso3D

There IS a middle ground. I prefer to use spots with geometry, which is sort of... a directed meshlight.

 

tl155180

Thanks for the suggestions. Yeah, I agree with you all. It does seem to be something to do with how the light is directed. Mesh lights direct light in 180 degree direction, whilst spotlights are more focused.

I might try a larger geometry for the spotlight in combination with a wider spread angle. Maybe that'll help. Thanks.

evilded777 - I've been using mesh lights for backgrounds and spotlights for figures too but I found that the figures kept coming out looking a little too cartoony in comparison to the scenery, whereas if I highlighted them with a mesh light plane instead (attached to the camera) the softness of the light looked more realistic. But I do like the way spotlights pick out the highlights better, makes them look more 3D, so I'm trying to find a happy medium between the two.

Oso3D

I've had decent results with 'spots' as 100-200 diameter just off camera. Good luck. ;)

 

tl155180

timmins.william said:

I've had decent results with 'spots' as 100-200 diameter just off camera. Good luck. ;)

 

Thanks Will. I'll give that a try when my current never-ending render finishes.

I was experimenting with geometries of about 50-100 diameter, so perhaps I just need to go bigger and wider. Oh the joys of time-consuming experimentation!

Oso3D

I also keep reminding myself that in the 'real world,' photographers and film-makers make use of all SORTS of tricks to get around the limitations of realistic lighting. Heh.

 

Tobor

Mesh illumination will always be diffuse; it's engineered in the Iray materials definition for them. So they'll never have the highlights a spotlight will have. As others have noted, you can change the spotlight to be an area light, which is then a cross between a focused spotlight (directional infinitely small point light source), and the diffuse light from a mesh.

If you must use meshes, there are some techniques where you can shape the light using IES profiles, but the exitance of the light from the geometry is still diffuse.

fastbike1

In photographics terms, a spot with geometry is essentially a softbox. Works the same as, but faster than, a meshlight.