VIZ4, daylight radiosity and textures

HeDaCoM · May 15th, 2002

hi, I can't get good results with VIZ4 and radiosity with logarithmic scale exposure control (for animation) textures are too bright.. but if i turn down the brightness then the scene doesn't seem like a daylight scene... I have tried to turn down the RGB level output in the material map.. this gets good results. but I think it's very complicated to get a realistic daylight scene with VIZ4. Also with the sunlight object, it tints everything with an orange tone too much. I don't like that. of courase you can change the color of the sun. but it's annoying... and. what about a sunlight object that changes color of sun over the time? I mean if you set the sunlight with time and date, it should be more red at the damn and dusk....

in short, I don't like sunlight simulation of VIZ4.

[ May 15, 2002, 03:33 PM: Message edited by: Hector ]

nisus · May 17th, 2002

Hi Hector,

I got a few tips that might work:
- set the physical scale to 9000 for simulating sunlight.
- use a radiosity override material: although the manual claims you don't have to use it, the results are more controlable and often much better.

check the user guide for more tips

rgds

nisus

HeDaCoM · May 18th, 2002

yes, thanks for the reply. you're a great moderator

you mean... yes I use the radiosity override material. But I don't know how to set the parameters to simulate materials properly... I mean.. Why do you want a light analysis tool if you can set the light properties very well but it's difficult to set material properties?
in lightscape, for example, you had some presets for different materials,(wood, concrete, plastic, glass etc) but here in VIZ I don't know how to set the materials for radiosity. is there any tip on this? thanks

nisus · May 18th, 2002

Hi Hector,

Personally, I don't think the material setup is very difficult in viz. If you use your standard materials in viz, you got very weird results, I agree, but the radiosity override material is really good if you DO NOT use the defaults values of course!

One reason why standard materials are not useful is because it uses the color as a reflectance scale. This means that white surface reflect more light than black surface, which is absolute nonsense because a highly pollished dark floor does reflect lots of light.
So that's it for using standard materials...

Just take a standard material and add a radiosity override material. Keep the existing material as a sub-material. Than change all the following parameters!

Reflectance scale: (this is the amount of light that gets reflected): set this value not higher than 0.85, because most surfaces don't reflect more than 85% of the incoming light.
(If you set this value higher than 1 (max 5), you got a very strange fx because the surface reflects more light than it receives... Only usuable for unreal/inhuman worlds)
DO NOT use this control to increase self-illumination! Use Luminance scale instead (see later)

Color bleed: I usually set this value to 0.5 or 0.6 for most materials and up to 0.85 for colored surfaces that you do want to color bleed.

Transmittance scale: this is the amount of light that gets transmitted through transparant surfaces. Be careful if you use this value, because the sum of transmittance scale and the
reflectance scale cannot exceed 1 in real life, because otherwise you'd end up having more energy after the light hits the surface than before!
tip: It's better to make the total sum around 0.95

(The default settings for these two values are both 1, with means that if a certain amount of light hits a surface, the same amount is AND reflected a 100% AND transmitted a 100%. So basicly you'll end up having twice the amount of light after the beam hits the surface...
see why the default settings are ludicrous?)

Luminance scale: use this for self-illumination. Around 500-1000 should be ok.

Indirect Light Bump Scale: again the default of 1 is very bad. Better use something between 0.1 and 0.5

So this is it about the material setup.

Another rule of thumb is to reduce the RGB Level for a bitmapped material. (I hardly do this myself, but the user guide keeps pinpointing this)

A final very usual tip might be to read the manual/user guide. There is lots of very usefull information in there.

rgds

nisus

HeDaCoM · May 19th, 2002

Thank you for the explanation. yes. the default values of radiosity-override are quite funny... I can set the values for a proper material manually and be careful about that, but it would be nice to have some buttons in this material to set all those values to the correct ones with a simple click selecting the type of material (wood, concrete, glass... etc)
thanks

nisus · May 19th, 2002

Hi hector,

Hope you liked the info. You can always make a library for these materials

nisus

samp · June 1st, 2002

I'm trying these settings, cause I usualy have too much colorbleeding.

But I thing there is one thing that isn't totaly right ...
It's the following

Quote:

Originally posted by nisus:
Reflectance scale: (this is the amount of light that gets reflected): set this value not higher than 0.85, because most surfaces don't reflect more than 85% of the incoming light.
(If you set this value higher than 1 (max 5), you got a very strange fx because the surface reflects more light than it receives... Only usuable for unreal/inhuman worlds)
DO NOT use this control to increase self-illumination! Use Luminance scale instead (see later)

Transmittance scale: this is the amount of light that gets transmitted through transparant surfaces. Be careful if you use this value, because the sum of transmittance scale and the
reflectance scale cannot exceed 1 in real life, because otherwise you'd end up having more energy after the light hits the surface than before!
tip: It's better to make the total sum around 0.95

(The default settings for these two values are both 1, with means that if a certain amount of light hits a surface, the same amount is AND reflected a 100% AND transmitted a 100%. So basicly you'll end up having twice the amount of light after the beam hits the surface...
see why the default settings are ludicrous?)

Because the settings you choose are infecting the settings they calculate.

So when VIZ 4 says that your created material will reflect 85% of the light, and you place an override material above that material, saying that reflection should be 0,5. In that case you would get 42,5% reflection (0,5 x 85%)

So both the 'ones' at reflectance and transmittance settings in the override are possible. It means that you aggree with the settings VIZ4 calculated.

Plz correct me if I'm wrong ...
I'm still a newby if I see what Nisus can do and knows

Greetz
Samp

nisus · June 1st, 2002

Hi samp,

To be honest, I don't know what your talking about: So when VIZ 4 says that your created material will reflect 85% of the light, and you place an override material above that material, saying that reflection should be 0,5. In that case you would get 42,5% reflection (0,5 x 85%)

I just don't get it. What do you mean by 'when viz says it reflects 85%'? Do you mean the reflectance settings before you add an override?
Because as soon as you add an override, this previous value does not account for anymore.
In my thought an "override" gets rid of the 'underlaying' values.

Great thing of the override is that it reflects an amount of light that you setup indepently of the color of material.
If you don't setup an override material, it is f.e. not possible for a black floor to reflect a lot of light. While this is okay for a very flat/dull floor, it's not good for highly reflective black tiles in most hotels or commercial buildings.

If you're not sure about the override material, do check the viz4 users guide

rgds

nisus

samp · June 1st, 2002

It looks to me that it's more like an adjustive layer then an overriding layer ...

Look at my example :

This is the normal material, taken from the library in VIZ4 and a little bit adjusted

Now when I make that material into an override material, keeping the old one, I get this :

See that both Reflectance and transmittance stay the same, when I use the standard settings of 1 in the override material. (So even if both are set to 1, I still do not have more then 100% light after the bounce then before ...)

Now when I change the Reflectance settings to 0,5 (They even call it SCALE, so it's a relative setting) I get this :

The reflectance result in half as much as I got before the change. It's not 50% (like in 0,5 = 50% of 1)

And yes maybe I should read the user guide, but I'm not the kind of reading guy

This just flashed thru my head when I was trying your settings ... (VERY good help btw! Thx alot, it realy helps)

Plz tell me if I'm making a mistake, I'm in a learning process

Greetz
Samp

nisus · June 2nd, 2002

Hi samp,

Well tnx a lot for your explaination. It's very solid with the pictures and so. I haven't noticed this strange behaviour yet and the user guide did not comment on this particulair thing. I'll have to check it myself

Give me one more night

nisus

May 15th, 2002	#1 (permalink)
HeDaCoM Senior Member Join Date: Apr 2002 Location: Spain, Europe Posts: 181 Name: Héctor Corcín	hi, I can't get good results with VIZ4 and radiosity with logarithmic scale exposure control (for animation) textures are too bright.. but if i turn down the brightness then the scene doesn't seem like a daylight scene... I have tried to turn down the RGB level output in the material map.. this gets good results. but I think it's very complicated to get a realistic daylight scene with VIZ4. Also with the sunlight object, it tints everything with an orange tone too much. I don't like that. of courase you can change the color of the sun. but it's annoying... and. what about a sunlight object that changes color of sun over the time? I mean if you set the sunlight with time and date, it should be more red at the damn and dusk.... in short, I don't like sunlight simulation of VIZ4. [ May 15, 2002, 03:33 PM: Message edited by: Hector ] __________________ Héctor D. Corcín http://www.iruditek.com/hedaweb

May 17th, 2002	#2 (permalink)
nisus Super Moderator Join Date: Mar 2002 Location: Gent Flanders Belgium Europe Age: 32 Posts: 3,276 Name: Evert Vandenberghe	Hi Hector, I got a few tips that might work: - set the physical scale to 9000 for simulating sunlight. - use a radiosity override material: although the manual claims you don't have to use it, the results are more controlable and often much better. check the user guide for more tips rgds nisus __________________ www.ams.be / www.nisusarts.com http://www.youtube.com/profile_videos?user=nisusCGA&p=r

May 18th, 2002	#3 (permalink)
HeDaCoM Senior Member Join Date: Apr 2002 Location: Spain, Europe Posts: 181 Name: Héctor Corcín	yes, thanks for the reply. you're a great moderator you mean... yes I use the radiosity override material. But I don't know how to set the parameters to simulate materials properly... I mean.. Why do you want a light analysis tool if you can set the light properties very well but it's difficult to set material properties? in lightscape, for example, you had some presets for different materials,(wood, concrete, plastic, glass etc) but here in VIZ I don't know how to set the materials for radiosity. is there any tip on this? thanks __________________ Héctor D. Corcín http://www.iruditek.com/hedaweb

May 18th, 2002	#4 (permalink)
nisus Super Moderator Join Date: Mar 2002 Location: Gent Flanders Belgium Europe Age: 32 Posts: 3,276 Name: Evert Vandenberghe	Hi Hector, Personally, I don't think the material setup is very difficult in viz. If you use your standard materials in viz, you got very weird results, I agree, but the radiosity override material is really good if you DO NOT use the defaults values of course! One reason why standard materials are not useful is because it uses the color as a reflectance scale. This means that white surface reflect more light than black surface, which is absolute nonsense because a highly pollished dark floor does reflect lots of light. So that's it for using standard materials... Just take a standard material and add a radiosity override material. Keep the existing material as a sub-material. Than change all the following parameters! Reflectance scale: (this is the amount of light that gets reflected): set this value not higher than 0.85, because most surfaces don't reflect more than 85% of the incoming light. (If you set this value higher than 1 (max 5), you got a very strange fx because the surface reflects more light than it receives... Only usuable for unreal/inhuman worlds) DO NOT use this control to increase self-illumination! Use Luminance scale instead (see later) Color bleed: I usually set this value to 0.5 or 0.6 for most materials and up to 0.85 for colored surfaces that you do want to color bleed. Transmittance scale: this is the amount of light that gets transmitted through transparant surfaces. Be careful if you use this value, because the sum of transmittance scale and the reflectance scale cannot exceed 1 in real life, because otherwise you'd end up having more energy after the light hits the surface than before! tip: It's better to make the total sum around 0.95 (The default settings for these two values are both 1, with means that if a certain amount of light hits a surface, the same amount is AND reflected a 100% AND transmitted a 100%. So basicly you'll end up having twice the amount of light after the beam hits the surface... see why the default settings are ludicrous?) Luminance scale: use this for self-illumination. Around 500-1000 should be ok. Indirect Light Bump Scale: again the default of 1 is very bad. Better use something between 0.1 and 0.5 So this is it about the material setup. Another rule of thumb is to reduce the RGB Level for a bitmapped material. (I hardly do this myself, but the user guide keeps pinpointing this) A final very usual tip might be to read the manual/user guide. There is lots of very usefull information in there. rgds nisus __________________ www.ams.be / www.nisusarts.com http://www.youtube.com/profile_videos?user=nisusCGA&p=r

May 19th, 2002	#5 (permalink)
HeDaCoM Senior Member Join Date: Apr 2002 Location: Spain, Europe Posts: 181 Name: Héctor Corcín	Thank you for the explanation. yes. the default values of radiosity-override are quite funny... I can set the values for a proper material manually and be careful about that, but it would be nice to have some buttons in this material to set all those values to the correct ones with a simple click selecting the type of material (wood, concrete, glass... etc) thanks __________________ Héctor D. Corcín http://www.iruditek.com/hedaweb

May 19th, 2002	#6 (permalink)
nisus Super Moderator Join Date: Mar 2002 Location: Gent Flanders Belgium Europe Age: 32 Posts: 3,276 Name: Evert Vandenberghe	Hi hector, Hope you liked the info. You can always make a library for these materials nisus __________________ www.ams.be / www.nisusarts.com http://www.youtube.com/profile_videos?user=nisusCGA&p=r

June 1st, 2002	#8 (permalink)
nisus Super Moderator Join Date: Mar 2002 Location: Gent Flanders Belgium Europe Age: 32 Posts: 3,276 Name: Evert Vandenberghe	Hi samp, To be honest, I don't know what your talking about: So when VIZ 4 says that your created material will reflect 85% of the light, and you place an override material above that material, saying that reflection should be 0,5. In that case you would get 42,5% reflection (0,5 x 85%) I just don't get it. What do you mean by 'when viz says it reflects 85%'? Do you mean the reflectance settings before you add an override? Because as soon as you add an override, this previous value does not account for anymore. In my thought an "override" gets rid of the 'underlaying' values. Great thing of the override is that it reflects an amount of light that you setup indepently of the color of material. If you don't setup an override material, it is f.e. not possible for a black floor to reflect a lot of light. While this is okay for a very flat/dull floor, it's not good for highly reflective black tiles in most hotels or commercial buildings. If you're not sure about the override material, do check the viz4 users guide rgds nisus __________________ www.ams.be / www.nisusarts.com http://www.youtube.com/profile_videos?user=nisusCGA&p=r

June 1st, 2002	#9 (permalink)
samp Member Join Date: Nov 2001 Location: Ghent, Belgium Posts: 99 Name: Lode Blomme	It looks to me that it's more like an adjustive layer then an overriding layer ... Look at my example : This is the normal material, taken from the library in VIZ4 and a little bit adjusted Now when I make that material into an override material, keeping the old one, I get this : See that both Reflectance and transmittance stay the same, when I use the standard settings of 1 in the override material. (So even if both are set to 1, I still do not have more then 100% light after the bounce then before ...) Now when I change the Reflectance settings to 0,5 (They even call it SCALE, so it's a relative setting) I get this : The reflectance result in half as much as I got before the change. It's not 50% (like in 0,5 = 50% of 1) And yes maybe I should read the user guide, but I'm not the kind of reading guy This just flashed thru my head when I was trying your settings ... (VERY good help btw! Thx alot, it realy helps) Plz tell me if I'm making a mistake, I'm in a learning process Greetz Samp

June 2nd, 2002	#10 (permalink)
nisus Super Moderator Join Date: Mar 2002 Location: Gent Flanders Belgium Europe Age: 32 Posts: 3,276 Name: Evert Vandenberghe	Hi samp, Well tnx a lot for your explaination. It's very solid with the pictures and so. I haven't noticed this strange behaviour yet and the user guide did not comment on this particulair thing. I'll have to check it myself Give me one more night nisus __________________ www.ams.be / www.nisusarts.com http://www.youtube.com/profile_videos?user=nisusCGA&p=r

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