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**dalomar_cg** · 07-06-2009, 09:30 PM

Re: Workflow, Lighting and Plugin

Well, glad to see you've given the world of biased renders a try

Originally posted by Pierredenorvege

I'm currently experimenting with vray and seriously concidering to switch from the oh-so realistic and simple, but rigid and fascinatingly slow Maxwell Render, to Vray. Mainly because a) I soon won't have access to a 100 core render farm, but also because b) a week or so of experimenting have scattered my negative view regarding biased renderers (really not dull, washed-out, fakes afterall

), c) the fact that my outdated, 3 year old laptop can make useable renders in 20 minutes, and d) the great flexibility it seemingly provides for the artist (compared to Maxwell).

Those seam like some pretty good reasons

I'll keep those in mind the next time someone asks me about the pros/cons of bias vs unbias rendering.

I've been reading alot the last week, and this forum, the vrayforcinema4d forum, and others, have been of great help, but i still have quite a few questions...

1. LWF (again). Am I right if i assume that the latest "Vray for Rhino" plugin takes care of this aspect for me or do i have to adjust the gamma of each bitmap and color separately? Do displacement and bump maps have to be gamma adjusted to be 110% correct with LWF?

Out of the box V-Ray takes care of all the LWF stuff for you. You have control of your input and output gamma values (which are at 2.2 by default), and V-Ray automatically corrects all textures AND picked colors. It does NOT adjust any colors that are used as grayscale representations of material parameters, so the transparency value of a layer is not gamma corrected because it doesn't "appear" in the rendering. So in short, its not something you really need to worry about.

2. Should Physical Sun and Sky multipliers be set to 1 (default value) for the most physically realistic result?

Yes, leave their intensities as they are for results being at physical levels. As you hopefully know, you will need to use the physical camera to properly expose the image.

3. I've read that Perfect White should be somewhere around 220,220,220. Does this meen that no separate rgb value in the entire scene should exceed 220 (color (219, 123, 67) is ok, while (232, 198, 54) is physically unrealistic)? What about black? I guess it's not physically realistic to use 0,0,0? What other "rules" should one consider when aiming for 100% realistic materials? (i really love this kind of information)

Ah, this is one of my favorite "unbiased" rendering "misconceptions". It is true that "Perfect White" is NOT 255,255,255, but to say 220,220,220 is "perfect" is a little misleading. Ultimately, if you're using a physical camera and adjusting exposure, then where that "perfect white" actually is is more or less up to you. Basically the biggest issue with having whites that bright is that the amount of light energy that is retained through the calculations is probably more than what you would see in real life. I think that unbiased renderers are very quick to draw a line somewhere in the sand (and they've chosen 220 apparently)...with biased rendering it is about what looks good and what fits with your scene. I'd advise against using 255,255,255 but by all means find out where that "perfect white" is for yourself

BTW, all those statements go just the same for 0,0,0...it just doesn't happen in real life. Personally, I'm much more likely to set a color closer to white than I am closer to black, but that's just me.

4. Is there a way to make sure that the exposure of a scene is "correct"? Like f.ex make a white plane perpendicular to the Physical sun vector, render, take a color sample of the plane and the adjust ISO or SS to make sure the rendered color = the material color? What when you use a non-linear color-mapping, like Reinhard? How do you "Vray Veterans" do it?

I would say make it perpendicular to the camera myself, but other than that it seams like you've got the process. Any math that you do will probably only hold up though with fully linear color mapping, but I'm sure with Reinhard at a medium burn value you'll be in the ball park. Again, I don't think that there are many people here that are doing exposure measurements on their scene to get correct exposure values. When I train users I generally introduce them to an exposure table (http://en.wikipedia.org/wiki/Exposur...amera_settings) as a way to "get their bearings" when setting exposure values.

What about color clamping? the 8. death sin or nothing more than a mater of artistic concideration?

I generally advise against color clamping unless there are artifacts showing up in the rendering. With V-Ray specifically, clamping colors, especially on an overexposed scene, will speed up a rendering, but this is at the expense of loosing that information. If that information is important to you, then you probably shouldn't clamp, but if it isn't, than do what you need to do.

And what about lighting a scene? I guess you override the materials with some shade of white, like (128,128,12

, and then start adjusting and adding lights. Is this mainly trial and error or do you follow specific guide lines?

I don't necessarily think that you have to "divorce" the materials from the lighting as much since there will be an affect on the brightness of the scene depending on what the shade of white you choose, but that's just me. I think that its more important to understand what you're looking to get out of your lighting (these fixtures will be brighter than those...I want more light coming from here) than having a regimented process. I've seen several methods work, and when I see people struggle with lighting its more because they're not sure what they're looking for in their results rather than not having a set method.

Two things I do advise are A) light your scene from most influence to least influence and B) try and solidify the affect of a given light before moving on to another light (but understand it may not be 100% correct). Both of these help prevent "bouncing back and forth" from light to light, which is the kind of situation you don't want.

5. As I've already mentioned, Vray for Rhino is beyond all expectations. But i miss some stuff "Vray for 3d studio max" have (like the dirt, fur, volumetric light) and some bitmap correction tools (some simple level and color corrections). Is this planned within overseeable future? If so, is it rude to ask when?

Almost every feature that is currently available *through V-Ray* in 3ds Max is on the boards in some sense or another. The additional V-Ray materials, as well as per object properties and Proxies, are on the list of things that will be in the next full version of VfR. Volumetric light is something that I'd like to get in there, but depends largely on how the development for other more pressing features go. As to when, its not rude to ask, but I don't have an answer for that. At the moment the development team is in the final stages of finishing up the new core that will be a part of V-Ray for SketchUp on the Mac (a Mac version of VfR is something we're getting ready for). After that we dive head over heals into development on the next full version and as that progresses we'll get more of a timeline.

I hope it's not rude to ask these questions, and while i don't expect professionals to reveal all of their "tricks of the trade" (only if you want to

), i really hope you can help me make a potential switch from Maxwell to Vray as smooth as possible.

Its not rude at all, and any questions that you have just keep them coming. Tons of people ask a variety of questions around here, so if you're wondering about something then just ask. I'm glad that you've been having a good time with V-Ray. I think you'll find that V-Ray can pretty much be as physical as you want it to be. There actually are unbiased calculation methods that you can use, and you can even set up progressive renderings too if you so choose. Just in case you ever get "homesick"

**jrharvey** · 08-06-2009, 01:00 AM

Re: Workflow, Lighting and Plugin

Just a few things I wanted to mention about personal use. I found myslelf having to use sub pixel and color clamping on almost every single scene to get rid of artifacts. Im not sure what settings to fix it otherwise since I never have caustics on (ive heard thats what causes it) but its almost always there.

I also find myself changing the physical sky and sun intensities alot with interior scenes sometimes with a multi of 5, 10 or even 20. WIth outdoor scenes I just leave it the way it is default. Even worse, they dont always stay at a 1:1 ratio. I am guessing that it has something to do with the human eyes natural ability to adjust for many different lighting intensities and make a room seem brighter than it really is? Of course thigs act MUCH different when you are not using the physical camera, sun and sky. I know I dont always do the correct things from lack of knowledge but it gets the job done.

**thomthom** · 08-06-2009, 03:59 AM

Re: Workflow, Lighting and Plugin

Out of the box V-Ray takes care of all the LWF stuff for you. You have control of your input and output gamma values (which are at 2.2 by default), and V-Ray automatically corrects all textures AND picked colors. It does NOT adjust any colors that are used as grayscale representations of material parameters, so the transparency value of a layer is not gamma corrected because it doesn't "appear" in the rendering. So in short, its not something you really need to worry about.

Why is displacement maps gamma corrected then? Is that because you "see" the displacement?

**Micha_cg** · 08-06-2009, 04:41 AM

Re: Workflow, Lighting and Plugin

Some years befor I bought the Maxwell beta and was quite happy about the image quality - but rendering was a hoppy only. Later only VfR helps me to get images done within the time frame of my clients and the quality I liked. So, my Maxwell license was never used for a commercial visualisation. I'm a fan of biased rendering. I have the feeling, unbiased rendering is wasting time for invisible effects.

For a quick start with VfR I posted a starterkit scene at the forum tutorial section. Maybe it help you.

White materials - often I used white materials at max greylevel 230. But this cause, that textures can be looking to bright and I must set a multiplier of 0.8 for all diffuse textures. But for what is needed the 80% limit? It's needed to avoid that to much light is reflected by the indirect light calculation. I think, if you use the light cache as secondary GI engine and set the sec GI engine multiplier at 0.8, than you get the wanted limitation and don't need to keep the colors below 230.

Colormapping - "reinhard" and burn 0.8 doe's a good job. But often I like to simulate an analog film curve with a flat upper end that helps to catch high intensities, helps to get smooth transitions between burned out areas and normal exposured areas. Here you find an example of the frame buffer usage (clamp output must be disabled to get a 32bit image at the framebuffer):
http://forum.asgvis.com/index.php?to...32154#msg32154

**dalomar_cg** · 08-06-2009, 08:03 AM

Re: Workflow, Lighting and Plugin

@John
Depending on what you're doing, these will pop up more often then not. Typically when you have glossy reflections and very bright light sources, they tend to pop their head up more. The issue (more or less) is that a given sample is taken that happens to be from that very bright source, which throws off the other aspects of the calculation (the "mean" value). This typically winds up causing that sampling to take longer, and in the end the pixel winds up being too bright because too many samples were taken from the very bright light source.

Also, if you're bumping up the sun intensity for interior scenes, I think you're going about it in a backwards sort of way. The sun doesn't get brighter when we go in side, our eyes adjust to the different light intensity. So for interiors, its recommended that you keep the sunlight at the same intensity, but adjust the exposure of the camera to achieve the brightness that you're looking for. This will also help keep any lights that you add at reasonable levels.

@Thomas
Displacement maps should NOT be corrected. From my tests they aren't, so if you're seeing something different then I'd like to know. What determines whether something is gamma corrected is whether you see its COLOR in the rendering. This pretty much limits it to Diffuse Color, Reflection Filter color, Refraction Color, Fog color, and Emissive Color. All of the rest of the "colors" or maps that are there describe parameters of the material and their colors do not actually appear in the rendering. Any maps you use for environment may or may not be gamma corrected depending whether they are an HDR or LDR image.

Originally posted by Micha

I have the feeling, unbiased rendering is wasting time for invisible effects.

Or wasting time for negligible differences

**Hoop** · 08-06-2009, 08:08 AM

Re: Workflow, Lighting and Plugin

Hi Pierre,

A while back, I too, switched from Maxwell to Vray. I can get an image quality VERY close to Maxwell in a fraction of the time. My clients get their images faster which helps to speed up the design process because decisions can be made in a shorter period of time since several design iterations can be made and rendered in one day. The speed and quality that Vray allows me to obtain is one thing that helps to make repeat clients.

At first, Vray can be a little intimidating becuase of all the settings. And learning Vray takes longer than Maxwell, in my opinion, but once you grasp the basics and learn how each settings affects your final render you'll be pumping out high quality imagery very quicky. I have my saved settings that I discovered worked most of the time, and to be honest, I don't touch 90% of the settings 90% of the time. I just import my settings and go. Generally, when I'm doing something a little tricky or in a setting I normally don't render in is when I need to play with settings. My point is, that if you are doing similar types of environments and renders most of the time, then the set up time with Vray will also be fast once you get used to it.

In the end, it doesn't matter if it's a biased or unbiased rendering, it only matters that you get the look, feel, and design intent across that you want out of it.

Anyway, I've been in your situation (with regards to switching from Maxwell to Vray) and wanted to share some thoughts. Hopefully they help you in making your decision.

Best regards,
Hoop

**thomthom** · 08-06-2009, 08:28 AM

Re: Workflow, Lighting and Plugin

@Thomas
Displacement maps should NOT be corrected. From my tests they aren't, so if you're seeing something different then I'd like to know. What determines whether something is gamma corrected is whether you see its COLOR in the rendering. This pretty much limits it to Diffuse Color, Reflection Filter color, Refraction Color, Fog color, and Emissive Color. All of the rest of the "colors" or maps that are there describe parameters of the material and their colors do not actually appear in the rendering. Any maps you use for environment may or may not be gamma corrected depending whether they are an HDR or LDR image.

Check out this post: http://forums.sketchucation.com/view...art=15#p148769
It's a simple gradient from white to black LDR.

Then the same test but this time with HDR map: http://forums.sketchucation.com/view...art=15#p148831

If I take the LDR test and set the Gamma correction for the displacement map to 0.4545 it will render like the HDR test.

**jrharvey** · 08-06-2009, 08:32 AM

Re: Workflow, Lighting and Plugin

Originally posted by Hoop

Hi Pierre,

A while back, I too, switched from Maxwell to Vray. I can get an image quality VERY close to Maxwell in a fraction of the time. My clients get their images faster which helps to speed up the design process because decisions can be made in a shorter period of time since several design iterations can be made and rendered in one day. The speed and quality that Vray allows me to obtain is one thing that helps to make repeat clients.

At first, Vray can be a little intimidating becuase of all the settings. And learning Vray takes longer than Maxwell, in my opinion, but once you grasp the basics and learn how each settings affects your final render you'll be pumping out high quality imagery very quicky. I have my saved settings that I discovered worked most of the time, and to be honest, I don't touch 90% of the settings 90% of the time. I just import my settings and go. Generally, when I'm doing something a little tricky or in a setting I normally don't render in is when I need to play with settings. My point is, that if you are doing similar types of environments and renders most of the time, then the set up time with Vray will also be fast once you get used to it.

In the end, it doesn't matter if it's a biased or unbiased rendering, it only matters that you get the look, feel, and design intent across that you want out of it.

Anyway, I've been in your situation (with regards to switching from Maxwell to Vray) and wanted to share some thoughts. Hopefully they help you in making your decision.

Best regards,
Hoop

I think you hit the nail on the head. Vray is great for DESIGNERS. More time can be spent on design rather than rendering. Every part about it can be streamlined and with Vray RT coming hopefully it will really make it one heck of a design tool. Also, am I the only one that prefers the image quality of Vray's biased engine over that of maxwells unbiased? It seems that no matter how long you let the thing render in maxwell it will still have a bit of graininess that just doesn't seem to go away. Vray can really get clean even when using DMC and such that supposedly causes grainy renders. You can always adjust it to render VERY clean images and still in the fraction of the time Maxwell does it.

**dalomar_cg** · 08-06-2009, 08:56 AM

Re: Workflow, Lighting and Plugin

Originally posted by thomthom

@Thomas
Displacement maps should NOT be corrected. From my tests they aren't, so if you're seeing something different then I'd like to know. What determines whether something is gamma corrected is whether you see its COLOR in the rendering. This pretty much limits it to Diffuse Color, Reflection Filter color, Refraction Color, Fog color, and Emissive Color. All of the rest of the "colors" or maps that are there describe parameters of the material and their colors do not actually appear in the rendering. Any maps you use for environment may or may not be gamma corrected depending whether they are an HDR or LDR image.

Check out this post: http://forums.sketchucation.com/view...art=15#p148769
It's a simple gradient from white to black LDR.

Then the same test but this time with HDR map: http://forums.sketchucation.com/view...art=15#p148831

If I take the LDR test and set the Gamma correction for the displacement map to 0.4545 it will render like the HDR test.

Okay Thomas, thanks for the info. I know that the conversion of "non color" images was something that came up when we were setting up gamma correct, so I guess displacement slipped through the cracks. Would you mind sending me the scene and the maps in question. That would really help me with this one. My email is fine.

**Pierreden** · 08-06-2009, 09:21 AM

Re: Workflow, Lighting and Plugin

@Delomar:
Thanks for your brilliant reply!

@Micha:
Do you render with linear colormapping when you apply that curve or is it in combination with some other algorithm?

@Hoop:
Good to hear! From the little time i have used and experimented, it feels like the vray workflow is alot more fluid than maxwell. Especially when making new materials ( and lighting ofcourse (I guess every aspect of rendering))

@Everyone:

I see one can choose between 5 different light units (Scalar, Lumens, L/m/m/sr, Watts and w/m/m/sr). Are any of these more "consistent" or predictable than others? What is "Scalar"?

Is there a way to see and alter the placement of an enviroment HDR in Rhino? If so, cant seem to find it. And why do i have to boost the multiplier to see its effect?

Tried the DR with IM and LC. But it seems like my two pc's didn't cooperated on LC. Is this a bug, or is it recommended to use another engine than LC when DR'ing?

And what is Light Portals. I read that they take Intensity and Color from the light behind it, but why use it? Does it convert the light into a "rectangular"-type of light or something? Could someone explain this for me?

Best Regards
Pierre

**dalomar_cg** · 08-06-2009, 09:42 AM

Re: Workflow, Lighting and Plugin

Originally posted by Pierredenorvege

I see one can choose between 5 different light units (Scalar, Lumens, L/m/m/sr, Watts and w/m/m/sr). Are any of these more "consistent" or predictable than others? What is "Scalar"?

Those are different lighting units. Scalar is just "CG Units" and don't really have a physical basis. I don't think that any one is more consistent than the other, but if you don't know what those units are and what they are trying to represent, then it will probably be a shot in the dark in regards to setting levels properly

Is there a way to see and alter the placement of an enviroment HDR in Rhino? If so, cant seem to find it. And why do i have to boost the multiplier to see its effect?

Nope, not yet. This is exposed through RDK, and we'll be adding support for a number of RDK features in the next full version. If you have to boost the multiplier a lot, then you probably have the physical camera enabled. Since HDRs don't have physically based illumination levels, you will have to adjust the multiplier to match the exposure settings of your scene.

Tried the DR with IM and LC. But it seems like my two pc's didn't cooperated on LC. Is this a bug, or is it recommended to use another engine than LC when DR'ing?

This is not a bug, but it is a limitation of the way LC is currently designed. This is something that is in the hands of the Chaos Group. They are aware of it, but I am not sure of any plans to change this. Depending on how long the LC solution takes to calculate and how long a DR'd render will take with DMC it may be useful to switch secondary bounces over. LC is the only thing that DR won't contribute to, so no need to worry about anything else.

And what is Light Portals. I read that they take Intensity and Color from the light behind it, but why use it? Does it convert the light into a "rectangular"-type of light or something? Could someone explain this for me?

They've come up in discussion a few times recently, and ultimately I am completely unconvinced of their usefulness and practicality. They are more or less used as a means to "collect" light and promote what would be GI rays to being calculated as Direct Light, but IMHO the benefits stop there.

Here's a thread that discusses light portals
http://forum.asgvis.com/index.php?topic=6227.0

**thomthom** · 08-06-2009, 12:26 PM

Re: Workflow, Lighting and Plugin

Okay Thomas, thanks for the info. I know that the conversion of "non color" images was something that came up when we were setting up gamma correct, so I guess displacement slipped through the cracks. Would you mind sending me the scene and the maps in question. That would really help me with this one. My email is fine.

At the bottom of each of those two posts I linked to you can download the .skp file and the displacementmap I used.

**dalomar_cg** · 08-06-2009, 02:52 PM

Re: Workflow, Lighting and Plugin

Will do...Thanks Thomas

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