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

Attached Images

	room1.jpg (3.8 KB, 79 views)
	room2.jpg (3.4 KB, 60 views)
	room3.jpg (16.5 KB, 121 views)

Attached Files

Room.zip (98.6 KB, 14 views)

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!

__________________
There is a light (in your eyes) that never goes out...............

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.

__________________
- Fran
If you must reinvent the wheel, remember that it works best if it is, like, roundish.

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.

__________________
- Fran
If you must reinvent the wheel, remember that it works best if it is, like, roundish.

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.

Attached Images

	no_shell.jpg (16.6 KB, 81 views)
	shell.jpg (16.0 KB, 83 views)

__________________
- Fran
If you must reinvent the wheel, remember that it works best if it is, like, roundish.

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.

__________________
- Harry

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)

Attached Images

1def.jpg (82.7 KB, 117 views)

__________________
There is a light (in your eyes) that never goes out...............