Linear lights and radiosity.(lightwave 7.5).

[Hector]

Hello:

 

I have a scene with several linear lights simulating large flurescent tubes in "blind boxes" along the walls.

 

I tried a test rendering using radiosity (interpolated) and I got this funny render with bright circular spots all over the place in a random fashion, as if I had many sport lights with a samall cone angle pointing everywhere.

 

The same scene rendered with raytracing produce the intended lighting efect, large bright areas over the walls. But I wanted the same effect in radiosity plus may be one or two bounces.

 

any idea why is this?

 

Hector.

[Allen]

Hector:

 

Could you post some images - may help

 

Thanks

[Hector]

Hello:

 

This is the image.

 

Thanks.

[Charles Gaushell]

Turn on noise reduction to start with.

 

It looks like your radiosity settings are all wrong. Try the default settings first and make sure you don't have too many lights in the same position.

 

Fprime will give you better results regardless. Worth going to Worley.com and buying it.

[Allen]

Yep. Have to agree with Charles.

 

If you cannot afford FPrime yet...

 

Change radiosity type to Monte Carlo. Set rays to 4x12 or 5x15. Indirect bouncing to '1'.

Then do something really obscene - increase your Ambient Intensity to 25 or 30% with a very pale blue color or colour :-).

Reduce your resolution to 360x240 with no anti-aliasing for the test renders.

 

(Actually - set the resolution to 160x120 or so - forgot how slow monte carlo is)

[Hector]

Hello.

 

Now I have another problem:

 

I have about 12 linear lights in the scene. Renderings are taking ages, even the the most basic settings with raytracing. It seems to be the reflections, if I turn of raytrace reflections in the render options panel, things move much faster. But I have some reflective surfaces and glass, so I need to render the reflections and at the same time I need to keep the linear lights.

I guess that many linear lights are not advisable but I need to achieve the effect of large fluorescent tubes.

 

The model is not very complicate. It is under the hundred thousand polygons.

 

Is there any soultion?

[Allen]

Working on the same type of project - any soft shadow type light is going to kill render times - a solution reduce the quality of the linear light to 2 or so. Also, and I'm not sure if this helps or hinders render times, set the fall-off of the light.

 

Here's a test I did when preparing for the scene I'm working on. Did this to test different fall off distances and intensities of the lamps.

 

I've got my lamps now set at Inverse falloff - 2m, intensity of 12.

[Allen]

Any luck yet, Hector?

 

Tell you, wouldn't do radiosity without FPrime. If there's any way you can afford that program - well worth the investment.

[IC]

I stay away from Linear Lights. They're unpredictable and take an age to render.

I've copied Allen's set up and used luminous glass on the lights and moving shadow mapped spots in place of linear lights with motion blur switched on.

[minus]

yup yup... I haven't used LW in a bit... (stopped only about a month ago).. but linear lights are all wonky in LW with radiosity. They take *ages* to render. You're almost better off resizing area lights if the light spread of a linear is important to you.

 

My fave settings..

 

4X12 monte carlo ... antialiasing set to low... adaptive same turned off.. shading noise reduction on.

[Hector]

Hello again:

 

Thanks everybody...

 

Things are now a little bit better. The funny "multispot" effect was due to having the antialiasing off. Setting it to low resulted in a more normal image in one quick test with radiosity.

 

However, I've been doing most of the tests in raytracing where I've managed to get decent rendering times by decreasing the Ray Recursion Limit from 16 to 8-10. (I think that helps as well with the radiosity). That's the only way I've found to make quick render tests with shadows, reflections and refraction all on.

 

I have linear lights under control as well, disabling the shadows makes render faster. The fall off is set to inverse of distance. I am getting the effect I want so far. I still have to test in radiosity.

 

I got this new book called Lightwave 8 Texturing (I am usgin version 7.5). which explains a lot of many obscure stuff (at least for me) about texturing that I had no idea how to use. So I am using now something called special buffers to soften reflections in the granite floor !!. So I've passed from "mediocre" to "poor" in Lightwave texturing, but keep learning.

 

I am going to try an overnight radiosity rendering and tomorrow I will post the image to see what you think.

 

thanks all

[duymeister]

The way I did radiosty (before fprime) was i used interpolation settings... usually something like 4x12 rpe; min. evaluation setting depends on your scene size... if it's a room, then i'd set it to anywhere between 6" to 1'0" turn OFF cache radiosity and turn ON noise reduction. go to your camera settings, turn ON motion blur. if you are doing one frame, then what will happen is that with each antialiasing pass, the computer will recalculate the radiosity and therefore give you different "splotch" patterns... but with motion blur on, it will average it all out making it look smooth. this works well for still images but will give you random splotches in animations. hope that helps...