Daylight system & Interior

[ninghai]

I tried to construct a very simple scene. A 4m x 5m x 2.2m box with flipped normal, and an opening, default material with "2-sided" selected assigned. Daylight systems, radiosity and logarithmic exposure control set.

 

image 1 is rendered in max with "Render Direct Illumination" option selected in the Radiosity paramenters.

image 2 is rendered in max with "Re-Use Direct Illumination" option selected.

image 3 is rendered in Lightscape using the model exported from max, and the default daylights in lightscape.

 

 

A couple of questions:

 

1. In image 1, why are there light leaks at the edge of the room? This should not be a modeling problem since I simply flipped the normal of a box. Image 2 doesn't have the leak. Why? (I used "Ray Traced Shadows" for the sun light, and the "Ray Bias" was set at 0.1.)

 

2. In image 1, why the anti-aliasing isn't at work?

 

3. In both images, why the room is still fairly dark? Should I simply tweak the exposure control? Or is there something I am missing like increasing the bounce strength? What should I do to make it brighter without adding fake lights?

 

3. A more general question, do you mostly use daylight system alone with radiosity on interior scenes, or do you add other lights?

 

4. Is it possible to achieve what lightscape does with just the daylight system in max? The lightscape image has both clear shadows and bright bouncing lights. Image 1 and 2 seems can only achieve one of them. I attached my max file too. Can some one help me to set it up correctly and post it back? I would learn a lot that way.

 

Coming from a Radiosity background in Lightscape, the max controls are really baffling me. I hope I am just one thin layer of paper away, and would really appreciate if someone can poke it through for me.

 

Thank you.

 

- Harry

[Juan Altieri]

1- with the daylight system, use logaritmic exposure control on environment settings to adjust the contrast and brigthness of the scene (you can make more brightness), on the rediosity parameters, you have 2 options to make the image looks better..

the first one i to have a very densee mesh (in subdivision meshing parameters put a small value), the second one is to use Regathering direct ilumination (adjust rays per sample similar than the skylight system)...

the first option means: more processing time for radiosity and less for the render (useful to make more than one image with the same radiosity calculation)

The second: low radiosity time calculations, so long rendering times....(depends on the rays per sample value)

 

I made some images only using a PHOTOMETIC dayligth system and the images looks real good.......(symilar than the lightscape sample you make)

 

Good luck!

[ninghai]

Juan, thanks for your reply. Can you post a real simple sample that you have? Or maybe you can download my sample and tweak it and post it back here. I would really appreciate that.

 

- Harry

[Fran]

Hi Harry,

 

Using a 2-sided material will slow things down when you render. Don't use it if you don't need it. Set your raytraced shadow bias to .01. If that doesn't get rid of the light leak, try enabling the 2-sided option in the shadow parameters.

 

You need to supersample the materials that sunlight falls on in order to get rid of the jagged light. See if enabling supersampling with the default settings for your material gets rid of it.

 

The amount of light that bounces up onto the wall from the floor depends on the reflectance value of the material.

 

Hope this helps.

[ninghai]

Fran, thanks for the message. I was able to get rid of the jagged shadow by turning on the the supersampling of the default material. Great tip!

 

However, I still can't get rid of the light leak after trying your suggestions.

 

I use the default material which is of type "standard". How can I increase the reflectance level of it? I can't seem to find a control for that except there is a "Refl. Level" in the "Reflection Dimming" group which didn't do anything for me even after i maxed it to 1.0.

 

Thanks again.

[Fran]

Hi Harry,

 

What kind of intersection exists between the floor and wall? Is the floor a separate slab? Does it overlap or meet the wall at an edge?

 

To display reflectance values in the Material Editor, go to the Radiosity tab of the Preferences dialog in the Customize menu and enable that option. You control the Reflectance value of a material by adjusting the Diffuse color or the Output parameters of a bitmap.

[ninghai]

Fran,

 

The scene is just a box with its normal flipped. So the wall and the floor are two planes that have a clean intersection on a line. You can download the max file I uploaded in the begining of the thread and take a look.

 

I was able to see the reflectance/Transmittance value in the material editor. However, after I change the diffuse color to a light gray (80% reflectance), the scene just become a bit brighter but still very bland. There is no comparison to the image generated by light scape.

 

What is the appropriate mesh size? My room is 4m x 5m x 2.2m (or roughly 12'x15'x7').

 

If you have a similar simple scene with the correct setup of the radiosity, I'd very much appreciate it if you can post here. You can also download the zipped max file and tweak it and post back. I think that may be easier for me to find out what was wrong.

 

Thank you.

[Fran]

Hi Harry,

 

I see that the window opening has a thickness. Does the entire box have a thickness? Single-thickness structures will leak light.

[ninghai]

Fran,

 

Ah, you are probably right. Since the room is just a box with normal flipped, it does NOT have any thickness. I will change that and give it a try.

 

Meanwhile what I am most concerned about is the lighting. Your image is so much closer to the Lightscape image I posted up there, and so much better than I have gotten so far in max. Did you use a single daylight system with radiosity? Do you think you can post or send me (ninghai@gmail.com) the max file you used to render them? I think by studying the max file I will learn the quickest of how to set up max correctly.

 

Thank you.

[Juan Altieri]

hi, i post an image made only with dayligth system and radiosity, i use a lighting override material in floor wood to increase the reflection (if you have dark floor colours you need that to make the image looks more brigther)

Rendered with regathering (250 rays per sample) and a mesh of 0,5 mts)

[Juan Altieri]

here the settings for radiosity and dayligth

 

BYE!!

[ninghai]

Thank you Juan. It is a very beautiful image. Thanks for the tips on material too. I am sure it will come in handy.

 

However what I really need at this stage is a sample max file. It could be as simple as a square room with a window. If you can make such a model (or use mine from the zip file) and set up the daylight system/radiosity correctly so that it can render an image closely to the lightscape image I posted, I would really appreciate. I know this is probably too much to ask, but i think that is the best way for me to learn.

 

Thanks again.

[Fran]

Hi Harry,

 

What version of Max are you using? I can only save to Max 6, but I'm happy to post the little sample scene that those test images came from.

 

One thing - be sure to use IES Sun in your Daylight system if you aren't already.

[ninghai]

Fran,

 

yes i have 6 too. and i am using IESun.

 

thank you.

[abicalho]

Hi there,

 

1st, the light leaks in your file come from the simple fact that your wall only has 1 face: the internal face. Make sure you model the wall as it is - with an inside and an outside - this way you will not have light leaks.

 

2nd, you cannot compare MAX and Lightscape if you have different light positions, different exposures, different meshing etc.

 

3rd, using a meshing of 0.5 is what's causing the lack of detail in your scene - use a smaller mesh size, but only for the objects that need it.

 

4th, why are you set to Exterior/Daylight? It is an interior shot.

 

5th, Ambient Color should always be black

 

I'm attaching a file here that makes things look nicer.

 

Hope it helps,

 

Alexander

[Fran]

Yey Alex! I couldn't find that scene I was talking about.

[ninghai]

Alex,

 

Thank you very much for posting the modified file. It is indeed remarkably better now.

 

i followed the Montree T.'s tutorial on this site for builing a quick model for a room. that's why i used single face wall with 2-sided material. i didn't realize this could cause light leak until you and Fran pointed out.

 

i guess the biggest problem with my original scene was the mesh size. now the image looks much more interesting with the finer mesh.

 

when u say the ambient color should always be black, do u refer to ALL materials? why?

[Fran]

...when u say the ambient color should always be black, do u refer to ALL materials? why?

 

I think Alex means the Ambient in the Environment dialog. For Max 6 and Viz 2005, Ambient and Diffuse colors should be locked in the Material Editor.