Sky Shader issue

[Nizar]

Hi to all.
Actually I'm studying a I3d tutorial: Rendering with softimage XSI Vol.1 A nice set of tutorials.
I'm at second Tutorial, the Dungeon, and here starts my problems: in the video tutorial, they use a Sky Shader (under Render>Pass>Edit), the first issue is about difference from object tabs: I have a different tab for my sun light, in video they have a standard light tab (with all the usually sliders like Umbra, intensity, angle ecc.) all under tab "soft light", in my sun light tab (this new light is automatically called XSI Physical Sun), I have not the usual Soft light tab with all the usual parameter, but a new tab and its name is Physical Sun Mia. My render is more darker then video tutorial example, I have different parameter (some like Haze and Red Blue shift cannot be cage and turn automatically zero) and, most important I can add other lights but no one appears in my render regardless the setting I doing (no effect if I add a high intensity value, or umbra or other), work only the Sun Light (and it is really too low and poor light). I have Softiamge 2011, tutorials are based on Softimage 7
Any idea about?
Thanks in advance

[Rork]

There have been changes in the sky/sun setup since v7, so that explains the difference in PPG layout and light behavior.

This shouldn't be any problem following the tutorial though, workflow will be mopre or less the same.
For the sunlight, the Haze and other parameters in the light are linked to the same parameters in the Sky system, so they work together.
That's why you cannot change them, the '=' in the animate widget will tell you this.

Regarding the dark renders have a look at these things:
- Are you rendering with FG turned on? If not, that will explain some of the issues.
- Also, the new settings in 2011 will add a tonemapper to the camera.
- Do you have the 'linear rendering' settings turned on in SI?

All these things are interconnected and have a big influence on your render.

I also recommend reading the part on the Sun/Sky bit in the mental ray PDF on the 'Architectural and Design Visualization Shader Library'. It's part of the SI install, or get the latest version at the mentalray website.

rob

[Nizar]

Thanks Rob for your time
I read the Help guide but under the Physical Shader Mia, and there is no answer about my issue (why cannot cage the Sun light intensity and why cannot render other lights)

This shouldn't be any problem following the tutorial though, workflow will be mopre or less the same.

Unfortunately no, this cage. In this tutorial after applying the sun sky, they add another Spot Light. I cannot use the spot light (or other light), because SI don't render it, regardless its setting.

Regarding the dark renders have a look at these things:
- Are you rendering with FG turned on? If not, that will explain some of the issues.
- Also, the new settings in 2011 will add a tonemapper to the camera.
- Do you have the 'linear rendering' settings turned on in SI?

- FG turn on or off don't cage the result (this confusing me)
- I don't know what is tone mapper, a fast search in F1 help PDF tell me it is a camera material, but in my render tree camera has not this node.
- Again, sorry, I'm a newbie, so don't know what is or where is linear rendering... if search on PDF guide I find too many voice about (render is a too used word)

[Rork]

Hi Nizar,

A lot of questions with no simple answers I'm afraid. I'm quite busy atm, so I don't really have time to go into all this any deeper.
I'll have a look into it upcoming weekend if you can wait that long, and provide you with some links and more detailed information.

In the meantime you can follow the link in my footer for some info on linear rendering etc.

rob

[Nizar]

Hi, don't worry, I will try again and take a look at your site.

[Hirazi Blue]

I think Max' post ("Reply #1") in this thread over at XSIBase might help you understand the "render other lights" issue a little better.
Two notable additions to the Physical Sky/Sun setup in SI2011 are AFAIK a change of shader for the physical sun (this was a "normal" soft light, but now is a "Physical Sun (mia)") and the fact that the setup "automagically" adds a "Photographic Exposure (mia)" to the lens shader stack of the selected pass.
;)

[Nizar]

Yes, it is exactly my issue
Thanks very much Hirazi! You save too many time

[Nizar]

Hi again. I found another issue in Dungeon Tutorial (video 2):
volumic area light, when apply this effect (from Render>Get>Property) we don't see nothing, regardless our setting (reflection, map size or other). Cannot use this in a scene where applied Physical Sky?
And SI give us a strange "orange" message in low bar: RC warn 0.4 area light ignored.

[Rork]

Hi Nizar,

I'll try to have a look at it today and see if I can translate the old to the new ;)

rob

[Nizar]

Hi Rork
thanks very much for your interest
I found this thread on XSI Base, a usual, useful post by Max:
http://www.xsibase.com/forum/index.php? ... #msg273923
If I try to separate in a different render pass the light it may work, but physical Sky look really hard to master if you want add non natural effect.

[Rork]

Hi Nizar,

Yes, after some fiddling with the volume light I found out the same thing ;)

I'll try to post my thoughts on the video somewhere at the end of the day, including some workarounds for some stuff.

For the Sun/Sky system, like Max stated, it was designed to be 'physically correct', and work in tandem with the architectural shader.
All light FX are basically all tricks..
And the Sun/Sky system is contolled by the position of the sunlight, just in real life. That's all the control you get.


rob

[Nizar]

Yes, after some fiddling with the volume light I found out the same thing ;)

Ok, so I'm not totally stupid

I'll try to post my thoughts on the video somewhere at the end of the day, including some workarounds for some stuff.

Thanks very much!

[Rork]

Hi,

I had some time to look at it before work found me again ;)

Here are some thoughts/notes:

Part 1 - Sunlight system:
- A tonemapper is now added to the renderpass in SI2011, and that is heavily changing the values for the lighting. Be sure to turn check your gamma correction in the preferences or tonemapper.
- The system is different from XSI 701, and now properly interlinked with sky.
- No value slider for the brightness for the sun. This is controlled by the position of the sunlight. Higher is brighter, lower less bright.
- Also the brightnes of the sky color changes when moving the sun. Like the real thing ;)
- FG has to be turned on for the Sun/Sky system to work properly.
- Shadow is turned on by default in Sun/Sky system

Part 2 - Volume Spotlight:
- You don't have to use the Area Light option for Soft shadows in SI2011. You can also use the Raytraces Soft Shadows option now with some low values forSoftness ands samples.
- Or still use the Area Light option and change it's values so it looks good.
- The volume/tonemapper combo is more or less broken, or never meant to work together. It's like mixing old and new.
You can test it though on a new scene without any Sun/Sky system or mia_tonemapper to the pass.
- Volume property. the values needed are way smaller now than the ones needed in the PPG or video. Start off with something like .04 for the Reflectance to get something similar.
- But it's better to use something like the parti_vol shader on the pass>volume to get similar results. Try creating a separate pass for this, so you can tweak it later in a comp.

I'll have a look later on, but I have to get to work now ;)

hope it helps,

rob

[Nizar]

- No value slider for the brightness for the sun. This is controlled by the position of the sunlight. Higher is brighter, lower less bright.
- Also the brightnes of the sky color changes when moving the sun. Like the real thing ;)

Nice, but IMHO a bit awkward, in Modo i.e., you can setting manual day time (insert hour, month ecc.)

Thanks very much for your help

Actually I have another issue: importons and final gathering cannot be used together? If I doing I receive an error message: "scene 04 warn 072134: importons and final gathering are on, globillum off", any idea about? This "globillum" do not compare in F1 help pdf
In tutorial are used together without any error message.

[Hirazi Blue]

Did anyone already log this issue with the volumic property as a potential bug officially?

[Nizar]

The volumetric is a problem only if you use physical sky, in other condition it work fine. So I don't know if it is a bug or not. IMHO, the real issue is in physical sky, pretty useless.