Best Practice for pointing an IRay mesh light

tring01

Recently become interested in mesh lights again since there are some really well designed ones for sale in the Daz store.  Pointing them seems to boil down to trial an error though.  Wish there were a better, faster, more accurate way.  Any advice?

SickleYield

Are you familiar with the Iray preview mode in your 3D window?  If you go to the Draw Settings tab with it on (or create one from Windows--Panes/tabs) you can set the scene to Interactive instead of Photoreal.  It won't look as awesome as your final render, but it'll give you a great idea where the lights are pointing in viewport, and it's faster than a test render.

SimonJM

You could also parent a camera to the mesh and use the camera to help the pointing and positioning

tring01

I think I totally figured this out.

1. Create a primitive plane as your emissive
2. Create a standard spotlight
3. Rotate the spotlight 90 degrees in X
4. Parent the plane to the spotlight
5. Aim the spotlight at your subject as normal (or point it at your subject).  It will bring the plane with it in perfect orientation.
6. Once you have everything set up, just hide the spotlight.  Only turn it back on if you need to reset your mesh light.
7. Enjoy!

 

 

tring01

SimonJM said:

You could also parent a camera to the mesh and use the camera to help the pointing and positioning

Yeah, thanks.  That sent me in the right direction.

Richard Haseltine

If you emitter is a primitive a) remember that lights can be assigned a shape and b) the Create Promitive dialogue allows you to choose which axis and facing the primitive has. For Point at to work with a plane set it to Y Positive.

tring01

Richard Haseltine said:

If you emitter is a primitive a) remember that lights can be assigned a shape and b) the Create Promitive dialogue allows you to choose which axis and facing the primitive has. For Point at to work with a plane set it to Y Positive.

Yeah.  Next thing I want to do is test the difference between a light set to a 3m square vs. a 3m square primative.  It the results are the same - then no need to use an emissive instead of a light.  Good tip on setting Y to positive.  I will use that, thanks.

tring01

Interesting...I did two renders.  One with mesh lights and one with spot lights set to the same geometry.  I couldn't get the amount of light right, but the effect seems almost the same.  AND the amount of time to complete each render was the same.  To my eye the shadows from the mesh lights look a bit softer.  More pleasing.  But that could be just the brighter render from the spotlights tricking my eye.  Hard to say.

tring01

Richard Haseltine said:

If you emitter is a primitive a) remember that lights can be assigned a shape and b) the Create Promitive dialogue allows you to choose which axis and facing the primitive has. For Point at to work with a plane set it to Y Positive.

Absolute face palm moment.  Yes.  Just selecting Genesis 3 as my point at object for the emissive plane works perfectly.  Duh!  Thanks for the help!

Tobor

tring01 said:

Interesting...I did two renders.  One with mesh lights and one with spot lights set to the same geometry.  I couldn't get the amount of light right, but the effect seems almost the same.  AND the amount of time to complete each render was the same.  To my eye the shadows from the mesh lights look a bit softer.  More pleasing.  But that could be just the brighter render from the spotlights tricking my eye.  Hard to say.

The spot version has better highlighting and looks more realistic, apart from being a lighter higher in brightness. There is more realistic (less flat) shadow detail around the neck in the spot version. It's always good to remember that shadows are a natural product of light, and our brain expects them -- realism is robbed when they aren't there, and should be. Even with paintings (consider Vermeer) our brains expect tonal detail. 

Unless you use IES profiles, light from an emissive is diffuse, like that reflected from a large card. It's great for fill, but you really do want some highlighting detail, which naturally will also cause a few shadows. For glamour shots, obviously you want to minimize the harsh ones. If you look at the work of Peter Gowland, perhaps the most renowned pinup/glamour photographer, most every set has highlights and shadows. In fact, some of his most famous work had pretty deep shadows. 

If you use geometries at all, consider using them as fill, in which case, accurate pointing is not all that important. You have the right idea with either pointing to the subject, or parenting a camera or spotlight, so you can use their views for aiming. The spotlight idea is better because you could also use its light as a "kicker" for the reflector.

For render speed, you run into problems with the geometry is unecessary multi-faceted, and/or has conflicting settings. It's always advised to create an emissive using the emissive shader, which resets the shader dials, rather than take an existing surface, and turn on its emissive property. The latter can end up unnecessarily complicating the render calculations depending on other settings on the shader.

evilded777

As a further note, a flat emissive surface has an angle of... 180 degrees? So if you did not set the angle of your spotlight to that, the lights are not the same. That's also not too realistic.

tring01

Tobor said:

tring01 said:

Interesting...I did two renders.  One with mesh lights and one with spot lights set to the same geometry.  I couldn't get the amount of light right, but the effect seems almost the same.  AND the amount of time to complete each render was the same.  To my eye the shadows from the mesh lights look a bit softer.  More pleasing.  But that could be just the brighter render from the spotlights tricking my eye.  Hard to say.

The spot version has better highlighting and looks more realistic, apart from being a lighter higher in brightness. There is more realistic (less flat) shadow detail around the neck in the spot version. It's always good to remember that shadows are a natural product of light, and our brain expects them -- realism is robbed when they aren't there, and should be. Even with paintings (consider Vermeer) our brains expect tonal detail. 

Unless you use IES profiles, light from an emissive is diffuse, like that reflected from a large card. It's great for fill, but you really do want some highlighting detail, which naturally will also cause a few shadows. For glamour shots, obviously you want to minimize the harsh ones. If you look at the work of Peter Gowland, perhaps the most renowned pinup/glamour photographer, most every set has highlights and shadows. In fact, some of his most famous work had pretty deep shadows. 

If you use geometries at all, consider using them as fill, in which case, accurate pointing is not all that important. You have the right idea with either pointing to the subject, or parenting a camera or spotlight, so you can use their views for aiming. The spotlight idea is better because you could also use its light as a "kicker" for the reflector.

For render speed, you run into problems with the geometry is unecessary multi-faceted, and/or has conflicting settings. It's always advised to create an emissive using the emissive shader, which resets the shader dials, rather than take an existing surface, and turn on its emissive property. The latter can end up unnecessarily complicating the render calculations depending on other settings on the shader.

Spent some time online looking at a few of his images.  It's a good benchmark for pinup work.  Thanks for the tip!

tring01

evilded777 said:

As a further note, a flat emissive surface has an angle of... 180 degrees? So if you did not set the angle of your spotlight to that, the lights are not the same. That's also not too realistic.

Quite correct.  Thanks.