Light Portal extended - Light environment

[Micha_cg]

Hallo,

today I was fighting with the lighting of a big room with big windows and a terrace outside. Area Portals in the windows dosn't work, because there was a break in the lighting between the room and the terrace.

I like to use HDRI environments. It is very helpful to get a natural lighting. Also the area light portal are great as turbo for the GI. (Thank you for the tool.)

My current scene works with big portals around the house with the room. The lighting looks good for my eyes. I'm happy. Now I ask me, could I use a big light portal box around my scene? Or is it a catastrophe for the render time?
It seems to work good with my three big portals and I ask me, could it be possible to enable a direct lighting calculation at the environment options? I could save to build a light box around the scene.

-Micha

[corey]

Light Portal extended - Light environment

Micha,

Can you give us a screenshot or two showing your scene?

Just curious, are you using any color mapping at all? Do you have a direct light acting as a sun?

Best regards,

Corey

[Micha_cg]

Light Portal extended - Light environment

Hi Corey,

no sun, only big light portals and a plane with light material as background.
I don't like to post WIP images, if I have not done anything I can, but I'm curious what you think.

At the moment I'm working on the fireplace. The goal is to get a feeling for the room. The furniture should be so neutral as possible. It's my first interior and I try to find a workflow for anything.

-Micha



PS: The frame in the image is from a "_renderwindow" test rendering. For the final I will use better GI and AA settings.

[Thomas An._cg]

Light Portal extended - Light environment

Micha,

How many subdivs did you use for the glossy parts of the fireplace ?

[Micha_cg]

Light Portal extended - Light environment

Thomas, I have used 20. You feel it could be more? Any suggestion how much?

[Thomas An._cg]

Light Portal extended - Light environment

Thomas, I have used 20. You feel it could be more? Any suggestion how much?

I think it looks good. There is a little bit of grain but it is not bad.

The reason I asked is because I am still trying to figure out a good range of subdivs for blured objects (anything above 40 is getting slow... I have gone up to 80). If you remember my coins scene, there were problems. Your scene does not have other metalic objects reflecting against the blurred object and it does not have caustics so at 20 subdivs it looks good so far.

[flipside]

Light Portal extended - Light environment

Hi Micha, of course you can use HDRI, but it will take a bit longer. The light portals are a trick to get more light into the room. Many people also use normal rect lights in the windows. Do you have store with ir map checked? If no, this gives you raytraced shadows, so very detailed.

Here is your image after 2sec of PS work.


Maybe I exagerated, but with such big windows, this lighting seems much more correct than your rather dark image with dark corners. I mainly adjusted gamma. You can do the same in vray by using gamma color mapping: dark=1 and light=0.455 (dark is a global light multiplier, light is the gamma control, 0.455=1/2.2). But your textures and colors will be washed out because they are not gamma corrected the other way around, so they get double corrected. If textures have a gamma control you can correct for this. You can do it in PS too but then you have to convert each texture first... Same for colors, you need a gamma 2.2 display curve to be able to adjust colors properly.

I use this technique in max all the time, and since then, I have no problems anymore with light not going deep enough in the room. For now it is a bit difficult to do in rhino, but this will maybe change one day. I choose gamma 2.2 because it is a standard.

I posted this link already a few times, but I believe this is very important so I'll do it again
http://www.gijsdezwart.nl/tutorials.php

[flipside]

Light Portal extended - Light environment

With that workflow, you'll be able to use hdri's much better too. Because hdri's are gamma 1.0 by default, while all your textures are probably around 2.2. If you use this hdri in a normal workflow, you'll get very colored lighting and high contrast, looking completely wrong.

[Micha_cg]

Light Portal extended - Light environment

Thank you Wouter to bring it here again. Yesterday I was working on the scene and I have wonder me, because something goes wrong. The textures looks dull or the lighting. Now I understand the gamma problem. I hope Joe can implement a texture gamma control in the next time.

What can I do now? I think, I will build a gamma 2.2 HDRI befor I start my final rendering.

[joe_b]

Light Portal extended - Light environment

I hope Joe can implement a texture gamma control in the next time.

Yeah I should be able to. At this current point the gamma will not read what the actual image gamma is, you will have to specify it explicitly each time. I think this will probably be fixed sooner rather than later. Baby steps right?

[glen5700]

Light Portal extended - Light environment

Hi Micha,
Nice rendering, I really like the couch modeling and the fabric.

Glen

[Micha_cg]

Light Portal extended - Light environment

Hi Micha,
Nice rendering, I really like the couch modeling and the fabric.

Glen

Thanks. But the couch models are free from www.ultra3d.com.

[Micha_cg]

Light Portal extended - Light environment

In the first image at the right side below the window are some GI artefacts. In this image I have used -3/-1, so it is ok. But now I have used -3/0 and get some artefacts again. What is the best way to avoid it - -3/1 or more IM subdivs?

[Thomas An._cg]

Light Portal extended - Light environment

In the first image at the right side below the window are some GI artefacts. In this image I have used -3/-1, so it is ok. But now I have used -3/0 and get some artefacts again. What is the best way to avoid it - -3/1 or more IM subdivs?

A few things to look:
Try leaving it at -3/-1 but use subDiv=80 for the IrMap and use QMC 0.85 and 0.002. You may also try to increase the density of the Distance parameter (Dist=0.5 or so). Also if you are using lights try setting their subdiv=20 (I think 10 is a little low sometimes ... but more than 20 doesn't help much either)

How are your LightCache settings ? I would try 1000 and 0.002

[Micha_cg]

Light Portal extended - Light environment

Thank you Thomas, I will try it. My LC parameter are 800-0.001. Do you have tested different subdivs for the secondary engine LC? I'm curious to know what will be the effect of a low subdiv.