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View Full Version : Specular and diffuse setting for lights



luka
04-11-2003, 02:03 AM
I was creating a scene as usual and found myself placing two lights one for diffuse and another for specular, then repeated this where ever I require light. Wouldn't it be cool if that could be controlled in the light attributes box so you would only need on efor the two main effects.

So in essence you have an additional diffuse setting and a specular setting of course you could apply different colours to the settings as well. Anyway just a thought.

marko
04-11-2003, 10:21 AM
sorry but i see some twisted logic here.

specular and difuse are reflection property of material not of light.

marko

ingo
04-11-2003, 10:52 AM
Well there is no twisted logic, just switch of all lights and play with your specular and diffuse reflection settings.
Instead of just switching spec and diffuse of and on i agree that an input field for % would be a nice idea. Just reminds me of the BRDF shader...

luka
04-15-2003, 08:08 AM
I should of made myself more clearer
with the diffuse setting it would be cool if you could change the settings say from a fluro tube lights to say a soft box light from a photo studio.

With the specular setting it would immitate the light source so say you set it to a fluro light well it would cast a rectangular specular shape, likewise with the soft box light it would cast a soft square shape on your object.

I have illustrated my idea for you. Just a thought.

Panikos
04-15-2003, 10:38 AM
Yes, I agree with the splitting of Diffuse and Specular values per light. I asked for this very long time ago in the old Newtek forums.

Having dual ray-tracing lights works, but is faster to have one with two separate properties. Its easy to code I assume.

Someone can say, I can adjust diffuse and specular from surfaces.
Sure, but it better to adjust one light than adjusting 100 surfaces.

Whoever doesnt like the separation, can keep the same values.

This function, will eliminate the No Diffuse/No Specular switches.

marko
04-15-2003, 12:53 PM
ok i got what you mean.

lets say that specular and difuse are nothing but reflection.
depending on surface (glossy or dull) material has specular (mirror like) or difuse reflection.

yes i agree that today specular only has point light shape, what is wrong. also i belive that lw should be able to mimic area and linear lights. Not to forget that it should also genetate correct specular from bright polygons (or could we call them object lights - IES in lightscape). Today you can turn on reflection and playing with reflection bluring you can simulate glossines! It is very slow process.

In prerendering stage lw should take care of which light types you have in scene and depending on glossines factor blur specular shape.

luka you made nice examples but there is one small mistake. soft box light would generate hard or soft specular depending on glossines of material! and it can only be controled by material glossines. if it would be controled from light menu it would be complete mess. other thing is light shape which can only be given as light property. if it was given in surface editor how could we control its rotation. etc.

to conclude:
specular reflection is property of material, and shape is propherty of light.

and newtek please support other light types as IES

marko

marko
04-15-2003, 01:02 PM
some links to old forum ;)

http://forums.newtek.com/discus/messages/2/11319.html?1012856198

http://forums.newtek.com/discus/messages/2/10940.html?1026320492

luka
04-15-2003, 02:45 PM
Hi Marko very intersting I see that was posted in 2001 and nothing has eventiated in lightwave yet. Here's hopping.

Yes I agree but I would be referring to specular transmission generated by the light. In the real world the specular highlight is the shape of the lightsource on the surface of the object correct? The objects can still have their own specular and diffuse settings. Perhaps these lights could be called geometry lights?

Panikos
04-15-2003, 03:36 PM
Marko, nice to see you around ;)
Thanks for reminding us those threads.
Rereading them, gives us more knowledge.

I was puzzled with the relation of Glossyness and Reflection, and reading those links verified that they are not related, but instead Glossyness is related to Specularity.

I was looking for such a relation, since LW Radiosity deals only with diffuse, evenly spread and unless reflection is involved you cannot control the spread of irradiance onto a surface. Adding reflections of course causes more rendering time.

Lately I needed a way to tune the brightness of reflections, and I wish I had a way to mix the influence of backdrop and RayTraced Reflection. Sometimes very bright reflection can become more even if I use a spherical reflection map. This averages the brightness of the reflection into more desirable levels.

Its a great challenge to study Light, I literally enjoy it and enjoy LWaving too :cool:

Panikos
04-16-2003, 04:08 AM
Here is a comparison of two images.

One with irradiance, and one with simulated Specular Reflection

Panikos
04-16-2003, 04:09 AM
and the other picy :)

Panikos
04-24-2003, 02:04 AM
A shader that adds white or custom color to the color channel multiplied by (Glossyness) * (by the amount of irradiance received)

After some tests, I figured that even if I use a very bright spot on the radiosity-emmitter, shading is still even on every surface receiving the irradiance.

So actually specularity is a simulation of Specular reflection that saves time, compared to soft reflection. This works on a traditional raytracer with lights.

The way radiosity is emmitted looks correct to me. The reply of surfaces to the radiosity need some extra touch to break this even look.

luka
04-27-2003, 08:54 PM
Hey I just found this it's quite interesting as it relates to what I was talking about.
Lumaobject (http://www.cebas.com/products/products.asp?UD=10-7888-33-788&PID=33)

Panikos
04-28-2003, 12:59 PM
I 've made several tests using gradients. The Specular reflection cannot exist without raytraced reflections. The way radiosity influences a surface is defined by Diffuse channel.

I think I made a cirlce, but it was fun :D