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slepalex

19.04.2024, 05:01

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Rainbow Room 1

Rainbow Room 1
Description:	More indirect light study with flattened spotlights The exact same scenario as the original, based or inspired by David's recent indirect light submissions. All indirect light is provided by soft edged spotlights. In the original the caustic "shadow" the glass ball cast on the sphere was a major giveaway of my spotlights, that there was only one light per wall. Each wall had a single light strength 100 with square fall-off. In the current example I have used 5 lights per wall each strength 20. The lights are arranged like a diamond shape with 1 at the top, 3 along the middle, and one at the bottom of the wall, creating a diamond or a tilted square. The idea being that the corners of the walls need less illumination. Anyhow the result is much better indirect light and the caustic is corrected. Increasing the number of lights 5 fold greatly increased render time so I lowered the rpp from 64 to just 16, thus the noisy shadows. The original took 20 minutes, this one took 51 minutes. Adding more lights even though they are weaker still adds greatly to the render time when premium settings are involved. Still I think it is a more plausible render than the original. I will e-mail this source file also for comparison. Feedback is surely appreciated.
Added by:	rashadcarter1
Keywords:	Rashadcarter1, bryce6.1
Date:	05.14.2008 19:32
Hits:	3122
Downloads:	68
Rating:	0.00 (0 Vote(s))
File size:	509.2 KB

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davidbrinnen
Admin

Join Date: 01.03.2004
Comments: 2224

This is certainly more plausable. I worry though that this would be out of the range of most users given that the render time on anything but a state of the art render machine would be prohibitive. Consider the pay off between getting rid of the soft shadow option on your spots and premium effects and increasing the number of spots. Possibly a ring of spots per face, say about 36, very weak, coloured, rendered in a standard way? On balance I've found increasing the number of lights to simulate soft shadows produces less noise and renders faster than the alternative.

05.14.2008 22:31

rashadcarter1
Admin

Join Date: 06.04.2006
Comments: 2610

Agreed once again. I am testing that very notion of many weak hard shadow sources. Basically it still creates a form of noise but it looks alot like an IBL with bands.

The more lights that are used per wall the better and more accurate the light bounce can be faked. For example I would assume the part of the wall nearest the light source would reflect more light than the areas farthest from the light source. I assume this should create a gradient of light intensity fading from brighter to dimmer over the surface of the wall. I do not think a ring shape would be proper, it would ned to resemble the shape of the wall itself with the points of light as evenly distributed as possible in distance from one another. A Ring would be hollow in the center and that would not be quite right. The greates intensity is usally concentrated at the center of the wall.

It is like creating a light dome but instead of a sphere it is shaped like a cube with six major sides. The idea being that light domes are still the best way to go.

05.15.2008 00:22

davidbrinnen
Admin

Join Date: 01.03.2004
Comments: 2224

Hmn... but given that the spots are very shallow and that the objects are some distance from the wall, a ring would simulate a hot spot in the middle because of the overlap. The main reason for suggesting a ring is because it is quite good at creating soft shadows. I have used grids of point lights before and found that the lights in the middle of the grid need to be weakened because of the overlap of surrounding lights. Could be though that I did not have things balanced correctly to have the desired effect. However by the time hunge numbers of lights are being employed with carefully tweeked settings then the method is in danger of becoming a bit too labour intensive. Light domes are good, but often even slower to render than IBL.

05.15.2008 08:26

Render Man
Member

Join Date: 11.10.2007
Comments: 358

I am still here and have been watching to see what you two are going to end up with on this bounce lighting. I like the idea of using radials and also faster render time. The question that I have and which I posted in the forum is what is the whole purpose of bounce lighting. When I was trying to do my Sedan scene with what I thought was going to reflected or bounce light so the main object (Sedan) would have more detail and a more natural lighting. At least this was my understanding or Richter's comments.

I was wondering why you are showing the lights in these trials as in photography bounce lighting is more about the subject and not seeing the lights. Is the whole purpose of bounce lighting is to create a more natural light and to bring out more details? Perhaps the lights in Bryce already do this without having to bounce them but again those of you who understand the science of lighting would know this better than myself.

My suggestion would be trying filters with radial or flattened lights in combination of low HDRI and forget faking a bounce. But again I am a novice at this so it could be I am not really understanding the problem totally.

05.15.2008 14:11

rashadcarter1
Admin

Join Date: 06.04.2006
Comments: 2610

RenderMan,

I know it seems hard to fathom why we need to bounce light but I can only say to you that without bouncing light stragetgies the render will never approach true photorealism. Reality is harsh and not easy to reproduce at least in Bryce. You have been with Carrara so long you may not even realize just how good it is as the task David and I are struggling to reproduce with these tests in good old Bryce. After clunking around in Bryce for a while you will gain a new and profound respect for Carrara, I am sure of it.

Did you ever read this wiki on Global Illumination?

http://en.wikipedia.org/wiki/Global_illumination

When you read this over and observe the images included in the article you will see what David and I are after. It is simple, real life features bouncing light and a 3d render in order to look as real as possible needs to bounce light as well. Bryce can only reflect colors this is not the same as light because light casts shadows, even weak lights cast weak shadows. This then is how I find myself using spotlights to help me recreate the example used in the Wiki report.

You perhaps are still not appreciating that Bryce is not Carrara and it is not doing things the way Carrara does them. Carrara bounces light when Gi and indirect are engaged, Bryce does not bounce light under any circumstance unless you place spotlights or reflections to fake that bounce. I think the issue for you is that you are still not making a clear enough difference between your direct light and indirect light sources. Right now you are seeing all lights as the same and you are even tuning them to very similar intensities. This is the flaw, the indirect lights should be much much weaker than you direct light sources. Instead of starting the scene with indirect light, you must first place your bright direct sources, then only introduce weak indirect sources as necessary. Hope this helps.

05.15.2008 18:39

Render Man
Member

Join Date: 11.10.2007
Comments: 358

I think that global illumination on this site you shared states. "Theoretically reflections, refractions, and shadows are all examples of global illumination, because when simulating them, one object affects the rendering of another object (as opposed to an object being affected only by a direct light). In practice, however, only the simulation of diffuse inter-reflection or caustics is called global illumination." So I think we are thinking the same thing I was only suggesting and was not clear that making the subject center of the effect as the light seemed to distract from how good the effect was. But I could be wrong as I don't have the understanding of the skills of those of you who have been working on this for some time.

I was trying to look at the main goal to be achieved rather than duplicate the method if this makes any sense. In other words think outside the box, if I may use this expression. Ha

I do like the lighting in Carrara but needed some better terrains so purchased Bryce and then come to like the materials and volume for making some neat effects. I am hoping that in the future the programs will integrate.

05.15.2008 21:14

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