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jrandom
02-13-2010, 11:36 AM
I'm trying to replicate realistic sunlight in space. I'd like to use a light with an image map where that image map is a white HDR image at full brightness and then use HDR exposure compensation (or whatever it's called in Lightwave) to hopefully get realistic-looking exposures in both exposed surfaces and surfaces receiving bounced light from radiosity.

1. The only material I've found so far is on how to combine multiple photographs in programs like HDR Shop, but nothing on creating an HDR image from scratch without using pictures. Is there a way to do this?

2. Are there any tutorials on adjusting the HDR exposure from within lightwave? I feel like I'm drowning in information, so any pointers to good, concise references would be appreciated.

The only imaging software I own right now is Photoshop CS4, although I'm willing to plunk down my hard-earned cash on other software if it is absolutely necessary.

8~

UnCommonGrafx
02-13-2010, 01:19 PM
Make a white picture at the highest bit level you can. A plane in lw with luminosity turned up real high so as to white out the pic comes to mind.
Save as hdr or exr.

jrandom
02-13-2010, 04:15 PM
Make a white picture at the highest bit level you can. A plane in lw with luminosity turned up real high so as to white out the pic comes to mind.
Save as hdr or exr.

Interesting, I shall have to try that.

What about painting my own light probes?

UnCommonGrafx
02-13-2010, 04:19 PM
You have to be able to "paint" in a color greater than 256/100%. As I understand, that is what will give you the "dynamic range" in HDRI: some of the image goes really low and some really high -- all of it preserved in the image and capable of being exposed all together, at once.
Blochi wrote a book of which I would suggest for anyone who wants to play with hdris and photographers.

jrandom
02-13-2010, 06:54 PM
You have to be able to "paint" in a color greater than 256/100%.

Yes, but how would I actually go about doing that? All my searches for creating HDRI lightprobes return results that center around combining multiple exposures from a camera, not painting in Photoshop or other software.

SplineGod
02-13-2010, 10:27 PM
You can for example use skytracer to make a sky with sun etc. LW will render that out in one of several HDR formats. You can use ACT with a spherical lens to create a light probe or replicate how its done in the real world with a reflective ball. :)

jrandom
02-13-2010, 11:21 PM
You can for example use skytracer to make a sky with sun etc. LW will render that out in one of several HDR formats. You can use ACT with a spherical lens to create a light probe or replicate how its done in the real world with a reflective ball. :)

... !!

So... If I were to create a luminous ball that was really bright (to represent the sun in space, no atmostphere), moved it a distance from the origin, then rendered with an ACT to a sphere out to an hdr format, I could then use that as an HDR lightprobe?

Cool.

toby
02-14-2010, 12:27 AM
The sun is approximately 65,000% white - trying to get that to look right in LW will have you throwing fits, and would take days to render 1 frame even if it did work. LW's not designed to do real simulations, they're not practical anyway. Use a cg light, it's indistinguishable from sunlight in renders.

jrandom
02-14-2010, 01:10 AM
The sun is approximately 65,000% white - trying to get that to look right in LW will have you throwing fits, and would take days to render 1 frame even if it did work. LW's not designed to do real simulations, they're not practical anyway. Use a cg light, it's indistinguishable from sunlight in renders.

So if I use a regular light set to above 100% and render out to HDR, I could (in theory) use some other program to properly expose the frames?

SplineGod
02-14-2010, 01:10 AM
You can set the sphere to a luminosity higher then 100%
The idea is to render something t hat looks correct or looks good rather then focus on making an accurate simulation. :)

jrandom
02-14-2010, 01:12 AM
You can set the sphere to a luminosity higher then 100%
The idea is to render something t hat looks correct or looks good rather then focus on making an accurate simulation. :)

I get that part, I'm just trying to figure out how to render with a higher dynamic range for later exposure so I can get more realistic-looking light for scenes where I wouldn't have an HDR lightprobe made from photographs.

SplineGod
02-14-2010, 01:43 AM
Lightwave internally stores the render as floating point (HDR).
The file format that you save the images in determine if that floating point data is preserved or not.
For example, TGA, JPG, BMP etc are not floating point and save out as LDR (Low Dynamic Range) or 24 bit only.
Radiance, Tiff(FP), SGI(FP), Cineon(FP), EXR etc do save out as floating point (HDR) data.
So if you have high luminosity surface, textures etc those renders will be saved with the HDR data if you
save in the proper file format :)
Also remember that lights themselves arent visible which is why you want to use high luminosity polys.

Kevbarnes
02-14-2010, 03:31 AM
These might help you.

http://zbyg.deviantart.com/art/HDRi-Pack-1-97402522

these are medium rez Image files about 3.5Mb see attatched Thumbnail Previews


There are hi-rez versions available also, but can't recall where I got them from now.They are public domain free Licence. I have the collection of hi rez versions, file size about 16 Mb each.

feelthefear
02-14-2010, 04:45 AM
I think this one will answer your questions: http://www.except.nl/lightwave/hdr/index.htm

feelthefear
02-14-2010, 04:47 AM
Basically, save as .hdr open in Photoshop, go to Exposure and shift gamma around.

*Pete*
02-14-2010, 05:48 AM
These might help you.

http://zbyg.deviantart.com/art/HDRi-Pack-1-97402522


thanks man...ill put them into good use right away.

jrandom
02-14-2010, 10:02 AM
These might help you.

http://zbyg.deviantart.com/art/HDRi-Pack-1-97402522

these are medium rez Image files about 3.5Mb see attatched Thumbnail Previews


There are hi-rez versions available also, but can't recall where I got them from now.They are public domain free Licence. I have the collection of hi rez versions, file size about 16 Mb each.

Oooo! Thank you!

jrandom
02-14-2010, 10:04 AM
I think this one will answer your questions: http://www.except.nl/lightwave/hdr/index.htm

Excellent! There's some great info there. The radiosity page is fantastic as well.

Y'know, this on-line community was one of the major deciding factors in my decision to buy Lightwave. You people are great.

shrox
02-14-2010, 10:56 AM
Excellent! There's some great info there. The radiosity page is fantastic as well.

Y'know, this on-line community was one of the major deciding factors in my decision to buy Lightwave. You people are great.

Word

toby
02-14-2010, 07:40 PM
Thought I'd try some ridiculous settings just for the funkovit.
Sun polygon at 65,000 luminosity (but oversized, larger than the sun, so that more rays would hit it)
Radiosity - brute force MC, 1 bounce
Rays per evaluation - 100,000 (yes a hundred thousand)
AA - none
Rendertime - 1hr 2sec. on an 8-core

LW actually managed a hard shadow! It's faint, to the right going back.

jrandom
02-14-2010, 07:48 PM
Thought I'd try some ridiculous settings just for the funkovit.
Sun polygon at 65,000 luminosity (but oversized, larger than the sun, so that more rays would hit it)
Radiosity - brute force MC, 1 bounce
Rays per evaluation - 100,000 (yes a hundred thousand)
AA - none
Rendertime - 1hr 2sec. on an 8-core

LW actually managed a hard shadow! It's faint, to the right going back.

Yikes!

I've not used luminous polygons yet. What are the luminosity units in? (eg. lights are a percentage... does 100% equal 100 (or 1) in luminous polygon units?).

What would that image look like rendered with the default ray counts using Final Gather? (eg. why are so many rays needed when using a very bright luminous polygon?)

Cool render test, though. What kind of computing power did you throw at it? (Eight cores, but at what speed? 32-bit or 64-bit?)

toby
02-14-2010, 09:29 PM
Oh don't worry, using luminous polys ("lumigons") doesn't really require extreme settings like those. The only reason I used 100k rays is because an object that is very small like my sun, in terms of the amount of area that affects the lighting of the subject, rarely gets hit by the rays that determine the lighting on a surface.

The direction of lighting with radiosity is the opposite of what you might think. Rays are fired from the shaded polygons in a 180 hemispere, to sample the environment that it's in. That's a huge area, so if you only use 256 rays, the odds of hitting something like the sun (which fills about 2% of the sky) are very small, and being hit by only 1 ray wouldn't change much anyway.

Lighting with lumigons is usually used for big diffuse light sources, like florescent lights, and can't give you the hard shadows of direct lights, because they can't be very small. They should be well above 100 luminosity to be considered light sources, 1000 is not unheard of. It just depends on your scene. I don't know if anyone's figured out the equivalents, but it's nowhere near 1 to 100, cg lights are far brighter than the lumigons.

jrandom
02-14-2010, 09:33 PM
Oh don't worry, using luminous polys ("lumigons") doesn't really require extreme settings like those. The only reason I used 100k rays is because an object that is very small like my sun, in terms of the amount of area that affects the lighting of the subject, rarely gets hit by the rays that determine the lighting on a surface.

Ah hah! Makes complete sense. Really freakin' obvious in hindsight.

I've just found the HDR exposure filter and it does exactly the sort of thing I was looking for. As George Carlin once said, "It's amazing how often the obvious solution eludes us."

toby
02-14-2010, 10:50 PM
Glad that made sense! I'm not the best at explaining things :P

Eagle66
02-16-2010, 01:17 PM
I recommend "Blochies HDRI SmartIBL" Tool for LW by Christian Bloch from Eden FX :dance:

Here is full Page of Tutorials to HDRI and a 20-minute tutorial screencast:
http://www.hdrlabs.com/news/index.php

Here is Loader Smart IBL for Lightwave:
http://www.hdrlabs.com/sibl/loader.html

Here is the HDRI-Handboock
http://www.hdrlabs.com/book/index.html

And here are HDRI Sets:
http://www.openfootage.net/?cat=15

Happy HDR :thumbsup:

http://www.hdrlabs.com/sibl/index_assets/sibl_lightwave.png

UnCommonGrafx
02-16-2010, 04:08 PM
Yeah, that stuff.

jrandom
02-16-2010, 04:15 PM
Here is Loader Smart IBL for Lightwave:

Interesting! I note that they set up a dome... is this so different maps can be used for color, specular/reflection, and lighting? Is there a method for this that works with using the regular background environment so that the HDR maps are at an infinite distance? (Good for scenes with a wide range lateral movement, I would think.)

I just thought of something else: What if you have an environment complex enough to require multiple HDR maps... how would that be set up?

For example, the movie "Moon" used multiple HDR setups to replicate the light for the entire moonbase so the robot/computer thingy could be lit correctly. Is this just a matter of applying the HDR maps back onto the geometry?

What about an outdoor scene... say a highway where a short section has trees casting shadows (altering the light for that section of road). What would be the preferred method of setting up the HDR environment so that the lighting would be correct for all CG elements, regardless of where they are on that road?

toby
02-16-2010, 04:46 PM
If you have the time and resources to make an animated HDR sequence, that's all you need. A hobbyist could make a cg sequence with a bit of work, but a photographed sequence is pretty much out of our realm. An easier way would be to use one base hdr and add low-res buildings or trees to affect radiosity as the subject moves. That wouldn't work with SIBL afaik, you need a real radiosity bounce.

jrandom
02-16-2010, 05:24 PM
If you have the time and resources to make an animated HDR sequence, that's all you need.

What if you have a single object that spans the entire length of road, or multiple objects (say, a traffic jam of cars) covering that area?

I'm trying to get a handle on HDRI lighting and there's just so much I don't know!

toby
02-16-2010, 05:33 PM
What if you have a single object that spans the entire length of road, or multiple objects (say, a traffic jam of cars) covering that area?

I'm trying to get a handle on HDRI lighting and there's just so much I don't know!
Well if the cars are not in the hdr already you'd have to add them anyway - that's when you'd use the low-res objects.

jrandom
02-19-2010, 12:04 AM
Here is Loader Smart IBL for Lightwave:
http://www.hdrlabs.com/sibl/loader.html

Urgh... I can't seem to figure out how to install this. I grabbed the script but don't know where to put it. I tried several locations within the Plugins folder but can't see anything in Layout that references it.

Edit: Nevermind, found it in Utilities->Plugins->Additional

alexos
02-19-2010, 02:34 AM
You know you can add it as a button, don't you? Just in case, edit-edit menu layout (or alt-F10), find it in "plug-ins" on the left and drag it under one of the "main menu" items to the right...

ADP.

jrandom
02-19-2010, 10:37 AM
You know you can add it as a button, don't you? Just in case, edit-edit menu layout (or alt-F10), find it in "plug-ins" on the left and drag it under one of the "main menu" items to the right...

Whoa... I can alter the entire button/menu layout?... I CAN! Go figure.

Tobian
02-19-2010, 12:00 PM
HDR point sources and radiosity just simply don't work together as others have said. If I want an HDR bright source, like the sun, I simply put a light, with inverse squared falloff next to a plane, and render that, save out the HDR and voila one sun light. If you make it slightly coloured then you can make colour temperature lights. I map the image to a inverse dome section, and then group a light with it. the HDR map is just used for reflections, so I tick the 'unseen by radiosity' setting for the object, and use the light to create the actual 'light' You could also use a dome light with a low angle, as they aren't too bad for speed either.

Using the HDR map for lighting alone results in BLOTCHES FROM HELL :D for HDR images to light scenes nicely they need to have a large but smooth dynamic range, but almost always the sun in them is not sufficiently bright to cast a hard shadow, it just doesn't work, and if it does, it'll be horribly blotchy because of the way LW calculates radiosity, or ultra-grainy if you don't use interpolation.

So long as you sufficiently naturally light an environment, you could use it's UV map to generate a baked environment, but except for simple scenes it's almost never of use, and you still need lights if you want to cast hard shadows. It's why you'll notice SIBL still uses them.

jrandom
02-19-2010, 12:12 PM
... the HDR map is just used for reflections, so I tick the 'unseen by radiosity' setting for the object, and use the light to create the actual 'light'...

Ah HAH! I was wondering how to solve that particular problem once I realized that a lot of what I called "specular highlights" were actually reflections of the original light source -- but could never figure out how to mimic that with the fancy new energry-conserving materials and regular lights.

Do you parent the dome directly to the light or do you wire it up some other way?

Edit: So if I use a dome light or DP Infinite light with a small angle setting, will this give me the proper "specular" sizes in reflective objects?

Tobian
02-19-2010, 01:07 PM
In my case the dome is a section of a sphere, so its centre is 0,0,0. The light is parented to it. If you rotate the dome, the light goes with it.

be careful to not confuse terminologies. There are principally two types of light reflection: Diffuse and specular reflection. 'specular' is a shader which (badly) fakes the effects of a specular reflection, but the illusion breaks down if the light is anything other than a point source. The 'size' of a light in no way affects the size of a specular highlight. That's controlled by the glossiness attibute.

If you're using a HDR to light, and surfaces which respond properly to reflection, then you should completelly disable specular, as it looks quite fake especially when shown next to real reflection based specular highlights. In terms of LW settings, 'glosiness' is analagous to 'reflection blur, but inverted. 99% glosiness will give a small very sharp hotspot reflection, in much the same as 1% reflection blur will give a small and sharp reflection of physical objects in the scene. In other renderers 'glossiness' is used to control both the ammount of reflection blur and the sharpness of the specular highlight. If you use materials nodes, they do the inverse and have a 'roughness' setting, which is basically the same as an inverse glosiness attribute.. a low value will yeild a tight reflection and a high value will yield blurry reflections and wide soft specular attributes.

Dpinfinite lights create a 'size' to the light source, but this only has any effect on diffuse shadow falloff and does nothing to either the specular shading or the reflections. it creates the nice soft shadows you get from area lights, but designed with a sun light in mind.

It's a pretty tough subject to get your brain round, other than to say to get realistic shaders you really need to ditch specular all together, and just use luminous polygons to act as reflector objects. Just remember that small tight luminous objects which are right enough to light a room, need to be several thousand percent bright, which looks fine in reflection but creates a horrible radiosity solution, so you are better off coupling them with real lights. Have the light cast diffuse light, and have the luminous object be your 'specular' and disable specular in the scene.

The next thing you need to work out is using Fresnel energy conserving methods, so you get realistic surface shading, but I think this already quite a long post! :)

jrandom
02-19-2010, 01:34 PM
In my case the dome is a section of a sphere, so its centre is 0,0,0. The light is parented to it. If you rotate the dome, the light goes with it.

Got it. I wasn't sure if you were doing anything fancy or not. Simple parenting of objects even I can do!


be careful to not confuse terminologies. There are principally two types of light reflection: Diffuse and specular reflection. 'specular' is a shader which (badly) fakes the effects of a specular reflection, but the illusion breaks down if the light is anything other than a point source.

Yes, I've already discovered that. :) I'm focusing my shading attempts using the energy-conserving materials almost exclusively now: Delta, Conductor, Dielectric.

There's a "specular" component, but it doesn't mean the same thing as the standard surface specular setting and I'm unfamiliar with how this new setting interacts with lights.

I'll be experimenting around with lights this weekend but was curious if you had an answer: Using the node materials above, if I use a dome light with a narrow angle or DP Infinite, will I get an appropriately-sized specular highlight or do I have to use a very bright poly so that the surface can reflect it? (eg. the difference between using an area light 3cm across and using a luminous sphere object 3cm across when simulating a light bulb.)

Should I be combining these, using a light source for illumination and a lumi poly solely to reflect in objects w/out affecting the rest of the scene?

Tobian
02-19-2010, 02:00 PM
Ahh the thing is you don't need to use the 'materials' at all, you can relatively easily make them yourself, and the 'materials' render slower. Of course I say 'easy' but then if you don't know what you're doing it's hard :D

the specular component in all materials is actually based on the cook-torrence specular shader, and in all cases is slightly broken, because Cook torrence is slightly broken, for very techy reasons haha. But suffice it to say you simply use the 'roughness' to alter the ammount of 'specular' but the values work roughly the reverse of the glossiness value, so the more roughness, the more spread out the specular gets, which is the opposite to 'glossiness'. I've found through experiment though that it's hard to get like-for-like correlation, so I am not sure how exactly they are done. If you're using HDR's and luminous polygons, just ditch spec all together. Solved :D

If you are simulating small lights then use very bright polygons. In LW terms a 'lightbulb' would be several thousand percent bright. The best results will probably come from a combination of real lights and reflector objects for your reflection-based speculars.

jrandom
02-19-2010, 02:37 PM
Now I'm really confused! Or rather, I'm confused about what I should be using to set up my surfaces. I'm feeling pretty solid on how the light itself gets bounced around.

1. Don't use Materials? Okay, so say I'm looking at an empty Surface node. What do I plug into it if I'm not using any Materials nodes?

2. If I'm using a Material such as Delta, you're saying to leave the Specular at 0 and control everything via the Roughness setting? (Assuming non-1D light sources, eg. luminous polys.)

My goal: I'm going to be doing a few CG establishing shots for a friend's short film. These all take place in space so I don't have to worry about atmospheres or multiple light sources. What I need is a way to have photo-realistic sunlight and materials, and I'm not afraid to throw more CPU cycles at rendering instead of taking "short cuts". (I'll learn the short cuts after I know how to do it the accurate, more render-intensive way.)

Tobian
02-19-2010, 03:03 PM
I was actually rendering up some basic sphere examples :D but my surfaces always end up looking really complex :D

When I say don't use spec.. you can actually turn spec off on the lights themselves, so you don't need to set up that property. In materials you can't disable 'specular' so don't bother trying too. you need to use roughness value to get non-mirror reflections, which you do need for realistic surfaces.

You know all that said about Spec. For a simple point light source it's not so bad to use, for space shots and such. It's just to get realistic surfaces you need reflection enabled too, and using reflection properly, with energy conserving is a little more complex.

jrandom
02-19-2010, 03:18 PM
Partway there! Yay!

Okay, so for, say, the Delta node, Reflection is controlled by the Specular setting... so how would one make a reflective Delta node? Would this be accomplished by turning off specularity in the lights and then up the Specular setting in the node to affect reflectivity?


Ahh the thing is you don't need to use the 'materials' at all, you can relatively easily make them yourself, and the 'materials' render slower.

I still don't understand this. What am I missing? How do you create an energy-conserving surface w/out using an energy-conserving material node?

Tobian
02-19-2010, 03:51 PM
Ugh, I think I am just confusing you haha.

Ok Materials work by pairing 'specular' and 'reflection' together. So if you increase the roughness, the specular highlight gets more spread out, and so do the reflections. They are twinned together so you don't need 2 values to do 1 thing. If you don't use the materials system, you need to do that yourself.

The term 'energy conserving' is a logic to building a material, and it is not a 'magic' thing you can only get by using the material nodes.. you can build your own energy conserving shaders without using 'materials'. It's just a little more timetaking, however it has some advantages, such as render speed.

'Energy conserving' is a term which basically means that no more than 100% of some light can be reflected off a surface. Bearing in mind 'reflections' and 'diffuse' are both kinds of light bounce/reflection. If you had 100% diffuse and 100% reflection, then you have a nonsense, because that's like saying you shine 100% light on a surface, and get 200% back again. When you are using 'specular' it's a fake effect, so it's kind of irrelevant that it doesn't balance with diffuse properly.

The thing which confuses some people here is that they assume that reflection is a 'value' either with textures, or with a single number, like say 50%. You shouldn't set your reflection like this, because it will make the diffuse look wrong. What you need to be doing us using a Fresnel curve falloff. In the node editor it's as simple as falling off a log :D Ok a little harder... You use a maths>scalar>Fresnel - and put a value into it. What the value is depends heavily on what kind of material you are making, which is the confusing part. Something like a paint, or ceramic, or indeed glass, it's set to about 1.5. Something like a metal will vary from about 2.7 up to about 20 for quite reflective chrome like materials. You feed the output into reflection. You then use an inverse node and feed the result into diffuse. This means that the remainder of 100% is in the diffuse shading, so whatever is not being reflected specularly, is being reflected diffuselly.

If you want to use textures.. Colour goes into colour as normal. 'gloss' or bluriness is fed into reflection blur and reflection variation is multiplied with the Fresnel node.

It's a fairly huge subject and you will probably find yourself messing on for ages trying to get it all right. The one thing I will tell you though is the preview sphere has to be ignored to a certain degree with 'realistic' shaders, because it can't show you what's in the environment, so unless you have an HDR map in your environment it would be that informative, and even then it's not telling you about how it's going to reflect what's around it, only the sphere. So the reflection Fresnel of 1.5 looks quite weedy and like it won't do much, but ignore that, it's going to look good when rendered :D

Tobian
02-19-2010, 04:23 PM
Ok here's some of what I mean. I started out with an energy conserving material (as I just showed up above) with a Fresnel of 1.6.

made a plane set to 100% luminosity, and parented a similarly sized area light with it, so the light would adjust with the plane..

Ok first render, looks nice, low reflection blur, and without any radiosity. the light spills out and gives a big soft shadow.

Next render, I enabled radiosity and disabled the light. Not quite as bright, but with a similar type of falloff and the reflections are not affected.

I increased the reflection blur in the next render, to simulate a low glossy value on a specular.

Next I shrunk the scale of the plane to 25%. The reflection is likewise smaller and the power of the light is much reduced. This is the thing about using radiosity or realistic light emission. LW lights would not lose energy like this, they just have a tighter umbra shadow, but remain the same same brightness.

To fix the power issue, I made the polygon 1200% bright. Now the light is much more powerful, but likewise the specular hotspot is much punchier. This is realistic. If something small is giving off enough light to fill an area, it should be giving off a very strong specular reflection.

You will also notice 2 things with the images though... 1) the light actually took longer to render and is a little granier, but the shadow is quite pleasing and crisp. 2) the radiosity engine is struggling to make the light falloffs 'smooth' and the brighter and smaller the light emmitter is, the blotchier the shadows and light appear.

Tobian
02-19-2010, 04:32 PM
Ok 2 more images going on with the same sequence.

Just messing on I made the surface more sophisticated, and layered 2 reflection shaders using a set of Fresnels to create a BRDF 'car paint' type shader. where you have a crisp reflection and a fuzzy one underneath, representing a 'gloss coat' over another softer metallic paint layer beneath.

Finally, I told the luminous polygon to be unseen by radiosity and enabled the light again. As you can see the light again has a lot more 'power' than the luminous polygon, even though it's set to 1200% brightness, and all of the blotchiness has dissapeared.

So basically polygons can provide faster and softer illumination, when using radiosity, but the fringe benefits only work for quite large areas of luminous polygons, otherwise you suffer from a power falloff issue, and blotching. If I had quartered the polygon again, the light would have been as crisp, but with sharper shadows, and the polygon's power would have dropped again. Turning up it's brightness a lot would have made a really powerful reflection (which would have been really grainy on the soft reflection) and made the radiosity solution really horrible and blotchy.

jrandom
02-19-2010, 04:36 PM
Oh oh oh! I get it! I GET IT!

Woo!

*bounce* *bounce* *bounce*

Now, about them luminous polygons vs lights... in that first render you're using a light w/ no specular and a luminous polygon w/ no radiosity? Is that the correct light/poly combination if one doesn't want to use only a lumi poly and absurd radiosity settings?

Also, would a... what was it called... a "lumigon" work here? Isn't that some kind of lumi poly to light conversion? I can't quite remember what the manual said.

jrandom
02-19-2010, 04:38 PM
Something like a paint, or ceramic, or indeed glass, it's set to about 1.5. Something like a metal will vary from about 2.7 up to about 20 for quite reflective chrome like materials.

I don't suppose there's a list of "correct" values for various materials, is there?

Tobian
02-19-2010, 04:55 PM
I sometimes say lumigon. It's just meaning a luminous+polygon, a portmanteau word (yes I had to look that up too haha :D) smushed up word.

What you might be confusing it with is the term 'luxigon' which is a tool within lightwave for converting polygons into lights, but for this type of thing is not quite what you need. It's a cool tool, look up the tutorials on what it does though :D

The final render uses the best combo for quality vs speed. A light which does not have specular turned on, and a luminous object which has 'unseen by radiosity' selected. So it can be very bright for specular hotspots on properly energy conserving materials, but doesn't lead to a blotchfest :D

as for the relationship between how luminous an object is and how bright a light is, that's a black art in LW - and best left to software that deals with such things, like Kray or or one of the fancy physically based unbiassed renderers, like Fry-render or Maxwell, of which LW is not :D

jrandom
02-19-2010, 05:01 PM
A light which does not have specular turned on, and a luminous object which has 'unseen by radiosity' selected. So it can be very bright for specular hotspots on properly energy conserving materials, but doesn't lead to a blotchfest :D

In your examples, are you using an area light the same dimensions as the luminous polygon? (If so, I may have to learn LScript so I can automate the process.)

I shall look up Luxigons as that was indeed the word I was thinking of.


as for the relationship between how luminous an object is and how bright a light is, that's a black art in LW - and best left to software that deals with such things, like Kray or or one of the fancy physically based unbiassed renderers, like Fry-render or Maxwell, of which LW is not :D

Crud. Not in my budget at the moment, but I'll put them on the list for future purchases. I think the next on my list is LWCAD. I'd like to get Vue as well, but I'm not sure if I want to get it soon or if I should just wait until CORE is out and Vue updates their product.

Any idea how Kray compares to FPrime?

(Setting a luminous polygon to 1000% luminosity isn't the same as setting a light to 1000%? That's gonna complicate things...)

You've been more than helpful. Thank you!

Tobian
02-19-2010, 05:01 PM
Erm I left them in my other pants? :p

Actually there are lists... If you have a look around, you will find pages full of 'ior' data, or index of refraction. Now like myself you may have wondered why there were ior values given for say brushed aluminium or Chrome, since IOR is for transparent materials? Well the IOR is the value you put into the Fresnel input, hence why they exist for non-transparent materials! :) There's some lists of them floating about...

Tobian
02-19-2010, 05:06 PM
Meh don't obsess too much about it. LW is not a physically accurate renderer, but it is a hell of a lot faster than using Maxwell :D Kray is a lot better, and I hear very good things about it, but like yourself I have limited funds :D

Just because it's a black art doesn't mean you can't do it, it's just a.. fudge about with it so it looks good kind of thing :D It's just if you're using energy conserving and reflection blurs instead of Specular it's going to look a WHOLE lot better than without...