Hey all,

I wanted to talk about realistic lights for a minute.

The following is quote from Bagginsbill:

"Because, as an example, real ceiling lights are rectangular or round boxes, not infinitesimally small points. The reflections from such lights are not rendered correctly when modeled as points.

Lights with a non-zero area (in some renderers these are called area lights) do not exist in Poser. But glowing props of any shape and size do exist, and I prefer to use them over point or spot lights."

That quote is from this thread:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2880290&page=2

But that got me to thinking about the actual structure of real lights, and the fact that we dont' really use anything like that in Poser at the moment.

Doesn't that seem odd to anyone else?

A standard lightbulb is comprised of a small tungsten wire suspended inside a glass bulb that is filled with an inert gas. We apply a current to the tungsten wire and the bulb lights up. So while the tungsten wire is not infestismally small, it is rather tiny and the actual source of the light.

We talk quite a bit about how truly realistic renders rely on proper lights and accurate materials. So why aren't we using accurate lights?

How hard would it be to build some realistic light props? And I ask that as a person that is completely incapable of producing that prop. :P

Anyway just thinking out loud and I was curious what other folks thought about the topic.

use poser capped cylinder to simulate fluorescent tube.  use hi-res ball to sim bulb light.  set ambient = ~10 or 100 or more; leave other channels zeroed. enable IDL as per settings in bill's marble thread.  they may have posted freebie realistic light props here or on sharecg.

p.s. recommend not using tungsten-filament bulbs. prefer LED bulbs, which contain array of flat surface-mount diodes, each ~5 mm square.

Bagginsbill is absolutely correct in his assertion and that fact is what prompted me to write Reality.

Lighting is 80% of your image and without realistic lighting it's very, very hard to achieve beliavable images.

The size of a light determines also the softness or harshness of the light. I see often that some people think that the harshness of the light depends on the brightness or the distance of the light to the subject. Both options are not correct. The harshness of a light depends on its size in relation to the subject. A large light generates soft shadows and a small light generates sharp shadows. 

Now, a light becomes larger in relation to the subject as the light gets closer. That's the only effect that the distance causes and it's usually the opposite of what is thought by artists who don't have photography experience.

In addition to those factors the color temperature of the light has to be beliavable and the exposure of the frame has to be set correctly. Let's take, for example, a scene set a midday, full sun. How do we control the brightness? In real life we cannot "dim the sun", that's an absurdity. Still, ask 10 photographers to shoot that scene and you will see 10 different exposures. Exposure is the way we control how much light we let go inside the camera. Not having that control is another limitation for the 3D artist.

In the pursuit of photo-realism the closer we are to the conditions of real life, the easier our job is.

Answering your question on why Poser doesn't have physical lights, the situation evolved over the years. Poser, like the majority of 3D programs developed in the past 20 years, uses a biased rendering approach. Biased rendering was designed to deal with the processors and technology available 10, 15 or 20 years ago. There were no expectations of photo-realism from the 3D programs back then so creating an infinitesimmaly smal light was no concern.

Cheers.

Yes but mostly it's the luminaire or light fixture that we notice in reflections.

Check this out - I finally got my Python library to cut round holes in walls. They work great as ceiling luminaires. Inside each is a point light. I could model an actual light bulb but it wouldn't make much difference unless I point the camera into the luminaires up close.

those cuts look great!  now you can do the screw holes for the hinge.

Yes indeed. I'm pretty stoked about it. I still would like the generalized boolean subtraction, but this is mostly what I need for a bunch of situations.

Those are absolutely awesome renders!!

I've had a similar thought in regards to regular lightbulbs, so you're probably right. It probably isn't worth the effort to recreate an exact replica when a point light inside a proper looking container will do.

What about fluorescent lights though? The glowing box is pretty simple, but it doesn't really give that multiple bulb effect that an actual light fixture would. Though I guess that just comes down to doing 3 glowing cylinders inside of a square fixture.

I'd love to know more about how you are making those holes btw, and an up shot into one of the light fixtures would be interesting to see as well.

Quote - Though I guess that just comes down to doing 3 glowing cylinders inside of a square fixture.

Yep.

I've been experimenting in a hobbyist kind of aimless fashion for about five years doing procedural geometry generation. What I like about it is the ability to model a family of objects with morphs so that I have a morphing prop.

This prop has morphs to change the dimensions of the box, the dimensions of the holes (diameter and depth), and I just added also a ring around the hole.

The cutout for the circle is done as follows:

Given any rectangle, I alter it to have a square hole in the middle by replacing it with four rectangles - left, right, top, and bottom.

Then I add four triangles to the hole, one in each corner, making it an octagon.

Then in each of those corners, another triangle to make 16 sides.

And so on, until I have 64 sides. Or 128. Or whatever.

The inner points I then extrude to form a cylinder. I close the back of the cylinder with a simple quad.

Then I add a lathed shape to make a nice rim around the opening.

All of these steps are controlled by python statements with dynamic parameters so I can change my mind about things without having to redo the model. I edit the script and run it to get the new model.

I modified the script to generate each step one at a time for this illustration.

The one with the light is blown out and all we see is white.

Here I tested my ceiling prop with 12 luminaires - in each is a point light.

The room is the Raleigh Tavern set that comes with Poser. I didn't yet fix the materials, which need a lot of work to be realistic, but the overall lighting looks pretty good to me.

then your geomatic method gives clean cuts without generating spiky triangles.  it's very ingenious!  in theory, user could do this with group editor, but would be extremely slow process without script.

perhaps another script could place array of point lites as desired.

I can't even being to explain how far over my head all of this is...

Very cool though! :D

Quote - perhaps another script could place array of point lites as desired.

Already did that as I said in last post.

Quote - Already did that as I said in last post.

oops, I missed that!  they are definitely gonna want this script.

Quote - I adjusted a few materials. Not bad. Unfortunately, the geometry of the room itself is wonky and not correct for Poser. So I'm not gonna waste more time on it.

Can I ask what you mean by that?

This causes havoc with how the shader interprets interactions with light. By me putting a proper wood shader here, it becomes clear that the geometry is totally messed up.

I marked up some of the issues I saw on just one section (fireplace).

The wood panels on the right here are behaving correctly. Those on the left are not.

And the fireplace has issues, too.

Quote - Well there are numerous places that either seem to twist from one set of normals to another, or actually have entire polygons with reversed normals.

This causes havoc with how the shader interprets interactions with light. By me putting a proper wood shader here, it becomes clear that the geometry is totally messed up.

I marked up some of the issues I saw on just one section (fireplace).

The wood panels on the right here are behaving correctly. Those on the left are not.

And the fireplace has issues, too.

Thanks for replying!

That's really interesting. I've had some serious issues with messed up geometry when trying to use Reality 3. I sent two of the sets to Paulo at Pret-a-3D and he said that the normals were all wrong. About 33% of the content that I've tried in Reality 3 has issues such as that, which is another reason that I gave up on using it.

I've had no such issues in Poser, as of yet.

Thanks for all the useful tips.

It is a shame that reversed normals are so pervasive in the poser world. Just sloppy modelling really.