Digital Art Zone

I don’t know about the rest of you, but I have muddled around with the sun in the sky settings and I cannot get a general light for daytime.

I’ll digress… I move the sun so that there is normal daylight - say 3pm on a normal (for England) hazy sunny day.

Now in real terms this would mean that the front of the building (south facing) would get the full light and effect, and the shadows would not be as strong as those given by the software. Bryce seems to think of light as being ON or OFF - nothing in between.

I cannot find any way to have reasonably strong sunlight yet weak shadows.  It’s great for effect I suppose but realistically light is not just on or off. If I rotate the viewpoint to the rear of the building it is unrealistically dark - The shadows would never be that intense so that it’s almost night.

So is there a way of controlling the intensity of the darkness given by shadows?  I have a house with a porch and the shadows it’s giving off are just too direct - you’d expect some light to hit the shaded area in some measure.

Thanks in advance for any feedback

Terry

Not sure why you posted this thread here in the Free Stuff/General Freepozitory section.

Anyways in Bryce you have control over how intense shadows are in the Light Lab in the Sun section toward the bottom of the window.

Another way is to add a Fill light coming from the opposite direction to the sun or just behind the camera at about 5% to lighten shadows or use True Ambience.

This is an excellent learning resource for Bryce http://www.daz3d.com/forums/viewthread/2839/

Moved to Bryce Discussion

I sincerely apologise for posting this in the wrong group.
I had the two groups open in different windows and I guess I got it wrong.
Many apologies.

@tdrd:  You can also find several lighting tutorials here, http://www.bryce-tutorials.info/index.html .  If you search You Tube you also find several on lighting.

tdrd - 23 September 2012 05:04 PM

I don’t know about the rest of you, but I have muddled around with the sun in the sky settings and I cannot get a general light for daytime.

I’ll digress… I move the sun so that there is normal daylight - say 3pm on a normal (for England) hazy sunny day.

Now in real terms this would mean that the front of the building (south facing) would get the full light and effect, and the shadows would not be as strong as those given by the software. Bryce seems to think of light as being ON or OFF - nothing in between.

I cannot find any way to have reasonably strong sunlight yet weak shadows.  It’s great for effect I suppose but realistically light is not just on or off. If I rotate the viewpoint to the rear of the building it is unrealistically dark - The shadows would never be that intense so that it’s almost night.

So is there a way of controlling the intensity of the darkness given by shadows?  I have a house with a porch and the shadows it’s giving off are just too direct - you’d expect some light to hit the shaded area in some measure.

Thanks in advance for any feedback

Terry

To my thinking it is a mistake to think of Sunlight shadows as being too intense. Many Bryce users approach lighting in the wrong way and have earned Bryce the reputation for creating low contrast images because of lack of shadows. Instead of wondering why shadows are so intense, it is best to ask yourself where the light you’d expect to see in the shadows is actually coming from in real life. In real life the sun gives shadows 100% intensity, but the shadows are lightened by the indirect light scattered by the atmospheric gases and also from light bouncing off nearby surfaces such as the walls of a building or the ground plane. In a realistic render, the secret is interaction, and shadow casting is an important type of interaction. Shadows are not the enemy.

You can always lower your shadow intensity in the Sky Lab. The Sun Shadow intensity slider is the reference for all other lights in the scene so if you lower the shadows of the sun to 50% then your radials will also have lowered shadows. This is one reason why I think it a major mistake in most situations to lessen shadow intensity for the Sun.

There are two forms of light people need to be aware of…Direct illumination and Indirect illumination.

Clearly and obviously the default sun and the standard point radial qualify as Direct or Key light sources. But for indirect light (which by the way is where the real realism occurs) is much trickier to make choices about.

Several tools are available in Bryce to help with indirect lighting. First is the Material Ambience. Ambience from a material applies a uniform glow to an object that can help to raise the darkness of shadows to something less intense. But the trade off is that the object will have lowered bump contrast and other things. Plus if you use too much and sometimes even 10% is too much you can accidentally create a glowing object which gives the impression of thermal heat radiance (think hot coals), not what you would usually want. So use Material Ambience very sparingly if at all. I should also state that Material Ambience is governed by the color of the Ambience swatch in the Sky Lab. If you make this swatch black, no matter how high you set the ambience of a material it will not glow at all.

Another Option is in the Sky Lab called Skydome. Skydome is basically a point radial positioned high above the Bryce world, shining light down directly onto the ground. The Skydome effect does not cast shadows so it cuts through solid surfaces which is physically inaccurate, because only those surfaces which face the sky directly such as rooftops and the ground plane are illuminated, vertical walls are left totally black. But Skydome is sometimes better than nothing. For me and my lean toward realism, I dont use Material Ambience nor the Skydome feature because they both reduce the realism of a render because they destroy shadows rather than correcting them. To turn off the Skydome feature just make sure the color swatch in the Skylab is fully black.

If you want realism (which you never said you were after, I know) here are a few considerations about lighting.

1. 2/3 of the Sunlight that strikes the Earth is scattered by the atmosphere, only 1/3 arrives as direct illumination and direct shadows. That means that if you are lighting a surface and most all of the illumination is coming from the sun alone then you have technically overblown your sunlight. Instead you should lower your sunlight and increase your indirect light.

2. Considering what I just stated above, it would stand to reason that the Sky and the sky color are the primary light influences for an outdoor scene with direct sunlight giving the emphasis. Direct sunlight should be the highlight, it should be the frosting, it should not be the entire cake.

3. Bryce 7 gives some really great tools for creating realistic indirect sky light. It is important to realize that indirect light casts soft but important shadows. Shadows are what give a model contour and form so preserving model detail while lightening the shadows is a paramount concern. IBL is a great way to do this. You can convert the current Bryce sky into an HDRI (dont worry about the names for now, just focus on what they mean to the render, as explaining IBL in one shot is not wise just yet). Anyhow, once you get the sky converted Bryce will then create a network of virtual radials arranged in a globe around your entire scene. These virtual radials will cast light into the scene from many angles revealing all of the model contours which is the way indirect light should always work.

4. Bryce 7 also offers Dome Lights and 3D Fill Lights, which also can form a network of virtual radials around your scene providing indirect light from all sides in a natural looking way.

5. But the most realistic is proper use of True Ambience. I say proper use because improper use will not look good at all. True Ambience is totally different than Material Ambience, so as not to confuse them. Material Ambience renders very fast and operates by assuming a uniform color as the environmental influence that lightened shaded areas of an image. Material Ambience is a very simplified manner of accomplishing the task. But it also doesnt ever look realistic.  True Ambience by comparison, actually is a form of GI and is related to the study of black body radiation. The point being, True Ambience calculates the real world values of bounced light from surface to surface, and is by far the most realistic in terms of results. But the render time is also 10x or more. So it all depends on you.

Szark - 23 September 2012 05:41 PM

Another way is to add a Fill light coming from the opposite direction to the sun or just behind the camera at about 5% to lighten shadows or use True Ambience.

This can indeed by a quick fix of sorts. A lot of it depends on how you plan to use the camera. If like many people, you set your camera position first and then build your scene around your one fixed camera position, then it is possible to cheat the multi-angular indirect skylight into a single point light positioned opposite the sunlight or camera. But this will leave some areas of the model receiving no indirect light at all. so if you move the camera too much this lack of light might become obvious. I still consider secondary light sources to be a better option than Material Ambience or the dreaded Skydome feature because at least standard radials cast shadows which help express model contours, and as mentioned above the shadows are the key to the realism, not the other way around. Light is hardly where the secret lies, shadows are the real deal.

I used to go about doing as Szark describes, but I dont like being bound to a narrow range of camera angles. So my solution to lighting is much more global, much more about covering all my bases, even the ones that aren’t visible in this current shot. For this reason I use only IBL, Domes, 3D Fills and True Ambience. IBL, Domes, and TA take much more time to render than Material Ambience and Skydome, so speed is an important consideration. If you don’t have the computing power for the better forms of light, use the cheap ones, just use them well.

I probably did not answer your question, but hopefully I have led you toward asking better questions. You are doing a super fantastic job of this project you’ve taken on and I want the final look of the light to be on par with the rest of your work.

Best of luck.

A relatively cheap way that gives sometimes acceptable results depending on the scene is positioning a radial light without falloff and without shadow casting at the camera position. It is a bit like using a flash light when photographing a scene. I use mainly IBL to get a distributed lighting. But it tends to create banded shadows. If the skydome is used to generate an HDRI, switching Sun Visible to off is the best choice most of the time. In this way, a nice ambient light can be accomplished that matches also the sky colour. Lighting, in general, is the most important part because there is no visual art without light.

Wow! Thanks for that extensive reply above - it certainly explains a lot.

Actually I am having a problem with some of my components.
I realise that when things are in the dark, or shadows, they are glowing.

For example the window ledge and lintols and soors simply glow white when they should be in the dark.

So one component is the windows themselves. I wanted white painted woodwork, so I added ambience to make them whiter. However this had has the effect of making them glow as outlined above. I have taken out the ambience now but the window frames are a dull white.
I have set the diffusion to white - what else can I do to lighten the paintwork?

Thanks in advance.
Terry

Rashad Carter - 24 September 2012 12:01 AM

1. 2/3 of the Sunlight that strikes the Earth is scattered by the atmosphere, only 1/3 arrives as direct illumination and direct shadows. That means that if you are lighting a surface and most all of the illumination is coming from the sun alone then you have technically overblown your sunlight. Instead you should lower your sunlight and increase your indirect light.

2. Considering what I just stated above, it would stand to reason that the Sky and the sky color are the primary light influences for an outdoor scene with direct sunlight giving the emphasis.

Sorry Rashad, this is fundamentally wrong, both technically and conceptually.

Taken as wide band energy, sunlight is only approx 30 percent weaker at the bottom of the atmosphere than at the top, as a result of all interactions excluding cloud cover. If we isolate the visible spectrum, the light is even less weakened. Scattering is only one of the interactions, so your 2/3rds reduction figure is impossible.

This is borne out by direct subjective experience (sunlit surface much brighter than shaded surface) and practical measurement with light meters. If an incident light meter is suspended three feet above the ground under a summer midday sun, it’ll measure about 120,000 lux. If a second incident light meter is placed on the ground in the shadow of the first, thus illuminated only by the entire clear blue sky dome, it’ll measure about 20,000 lux.

So on a clear, bright day (I remember those) direct sunlight is approx five times brighter than the sky dome light. Direct sunlight is vastly more significant to a (clear day) outdoor scene than the sky. A photographic analogy would be the sun being the key light and the sky being an all-round fill light. The sun is the gooey, creamy, sumptuous big slice of glorious cake that you stick your whole face in and go gaaaarrgggghhhmmmmpphhhh, and the sky is the marzipan you leave on the side of the plate.

Of course it’s possible to have local effects of haze, etc, in which the proportion of direct sun and sky dome illumination are more equal, but - so long as the sun is shining directly at any level - it will always be brighter than the sky. If you can see a shadow from the sun then the sun is - by definition - brighter than the rest of the illumination.

In terms of lighting a 3D scene, it should be remembered that the human eye-brain combo has evolved to have a large latitude when it comes to accommodating different light levels (much better dynamic range handling than digital imaging sensors and photographic emulsions). So a realistic looking scene is unlikely to result from a sun brightness setting five times greater than the ambient light chosen.

_ PJF _ - 24 September 2012 06:48 PM

Rashad Carter - 24 September 2012 12:01 AM

1. 2/3 of the Sunlight that strikes the Earth is scattered by the atmosphere, only 1/3 arrives as direct illumination and direct shadows. That means that if you are lighting a surface and most all of the illumination is coming from the sun alone then you have technically overblown your sunlight. Instead you should lower your sunlight and increase your indirect light.

2. Considering what I just stated above, it would stand to reason that the Sky and the sky color are the primary light influences for an outdoor scene with direct sunlight giving the emphasis.

Sorry Rashad, this is fundamentally wrong, both technically and conceptually.

Taken as wide band energy, sunlight is only approx 30 percent weaker at the bottom of the atmosphere than at the top, as a result of all interactions excluding cloud cover. If we isolate the visible spectrum, the light is even less weakened. Scattering is only one of the interactions, so your 2/3rds reduction figure is impossible.

This is borne out by direct subjective experience (sunlit surface much brighter than shaded surface) and practical measurement with light meters. If an incident light meter is suspended three feet above the ground under a summer midday sun, it’ll measure about 120,000 lux. If a second incident light meter is placed on the ground in the shadow of the first, thus illuminated only by the entire clear blue sky dome, it’ll measure about 20,000 lux.

So on a clear, bright day (I remember those) direct sunlight is approx five times brighter than the sky dome light. Direct sunlight is vastly more significant to a (clear day) outdoor scene than the sky. A photographic analogy would be the sun being the key light and the sky being an all-round fill light. The sun is the gooey, creamy, sumptuous big slice of glorious cake that you stick your whole face in and go gaaaarrgggghhhmmmmpphhhh, and the sky is the marzipan you leave on the side of the plate.

Of course it’s possible to have local effects of haze, etc, in which the proportion of direct sun and sky dome illumination are more equal, but - so long as the sun is shining directly at any level - it will always be brighter than the sky. If you can see a shadow from the sun then the sun is - by definition - brighter than the rest of the illumination.

In terms of lighting a 3D scene, it should be remembered that the human eye-brain combo has evolved to have a large latitude when it comes to accommodating different light levels (much better dynamic range handling than digital imaging sensors and photographic emulsions). So a realistic looking scene is unlikely to result from a sun brightness setting five times greater than the ambient light chosen.

PJF,

It may well be wrong, but there are some reasons to give it come consideration anyway. The proportion described by the 2/3 skylight 1/3 direct light is not an arbitrary assumption on my part. I got the formulation from this and other articles that detail and graph how this proportion works. I assume this statistic is based on the total potential of light, not necessarily applicable to every situation. I can find other articles as well but there is a quick wikipedia reference

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

“Diffuse sky radiation

Diffuse sky radiation is solar radiation reaching the Earth’s surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. It is also called skylight, diffuse skylight, or sky radiation and is the reason for changes in the colour of the sky. Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.”

The important processes in the atmosphere (Rayleigh scattering and Mie scattering) are elastic processes, by which light can be deviated from its path without being absorbed and with no change in wavelength.

The original article details it a bit more and explains the exceptions many of those you mentioned in your post. The 2/3 to 1/3 ratio has provided me some very stable outdoor lighting rigs lately so I am beginning to support it as a general starting point. The more objects that are around to obstruct the sky the more it can throw off this proportion. We also have to consider as you mentioned the other surfaces which can bounce direct sunlight.

Rashad Carter - 24 September 2012 07:04 PM

(quoting wiki page)
“Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.”

Read that more carefully, Rashad.

It says 25% of the direct sunlight (when the sun is high in the sky) is removed by scattering.
Of that 25% scattered light, two-thirds reaches the earth.

Two-thirds of a quarter isn’t a million miles away from a fifth…

_ PJF _ - 24 September 2012 07:57 PM

Rashad Carter - 24 September 2012 07:04 PM

(quoting wiki page)
“Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.”

Read that more carefully, Rashad.

It says 25% of the direct sunlight (when the sun is high in the sky) is removed by scattering.
Of that 25% scattered light, two-thirds reaches the earth.

Two-thirds of a quarter isn’t a million miles away from a fifth…

 

Ah, true indeed. In fact the actual total of such an arrangement is actually around 1/6, you are most certainly in the ballpark. I do not intend to disagree with that part of it.

For the sake of simplicity I had not gone too far into the other issue of describing albedo and how that should be factored into the intensity total chosen for the IBL. I was explaining to the OP that IBL would be a good way to go about the indirect light. Typically, users when thinking of IBL are concerned only with the light radiating down from the sky but that is only half the picture and only half of what IBL can do. Considering the Earth’s Albedo is around. 34% meaning that there is a lot of indirect light being bounced back upward toward space that the IBL needs to also account for.

To get the total value of indirect light for a scene, the light being bounced back upward by the local environment to my mind should be added to the influence of the diffuse sky radiation which we will estimate to be about 20% which reveals a rather different total ratio for indirect lighting, though still not 2/3, it moves closer to 50/50. My goal was to encourage the OP to using the IBL for more than just the skylight, but also for ground light as well which is what I was implying but not stating properly. Naturally the albedo varies based on the brightness or darkness of the ground level components, so the 2/3 ratio I am giving is assuming we er on the side of little too much light rather than too little. In most scenes there are terrain mountains building and other items that are going to block much of the distant traveling light from an IBL probe. Using the 2/3 ratio ensures that even with fully mature shadows and lots of obstructions there should be enough light to make everything look natural even in a dense landscape or cityscape.

I should probably explain a little further what I intend. In that long post I started using the terms indirect light and skylight a little too synonymously. In my own scenes I have developed what I call the EarthGlow Dome Light Strategy. It breaks up the elements of the outdoor light into three stages, Direct sunlight, diffuse skylight and diffuse ground level EarthGlow. The current proportions for a surface illumination are 2/3 indirect light split between the skylight dome and the Earthglow Dome with the Earthglow Dome a little brighter overall than the Skylight dome. The reason is as you observed, the sky itself can only do but so much but once skylight bounces off surfaces it in a sense gets brighter, amplified. Or another way to think of it, not all skylight is absorbed the first time it strikes the Earth so how do we account for the skylight that continues to bounce around from surface to surface? Clearly sunlight is intense and bouncing from surface to surface as well.

Complicated multiple dome strategies are probably out of his league for now. But in time. For now he will probably have to try to do everything in one shot with the IBL.

When we consider a scene like the one he is constructing with lots of sky, but also lots of obstruction by buildings and trees, he will need more light than expected.

Using one of my own works as an example, I have uploaded two versions of a scene I’ve been working on for a bit.

The original version played it safe with all of the indirect light intensities right around the 1/6 range you described. Since the sky is dark blue, I assumed it would scatter only a small amount of light. The ground level light was also conservatively set. The light in this scene was intended to be that of a vivid mid-day tropical type of environment based on the basic rules. Over the next few weeks I noticed that sometimes when I re-viewed the image it no longer looked as my mind remembered it, it looked a bit like evening, like the sun was setting even though it was high in the sky, the shaded areas were just too dark. Why doesn’t it look like vivid daytime every time I look at it? What missing? God knows the sunlight is plenty bright. What must I do next?

I played around with the balance of total indirect light to total direct sunlight and discovered that to produce the vivid daylight I was after I’d need a lot more indirect light than I’d ever imagined, far beyond the 1/6 proportion because I needed to account for stray rays of light flying around all over the place.

So here is a comparison. The original render used Bryce trees, the new one uses Carrara trees and I’ve even begun a new generation of trees because I dont like the way these turned out.

Anyway, to my mind the second version does a much better job of creating that sense of vivid daylight than the original render.

As always I am open to your feedback and respect your ideals so please provide any insights you can.

I have also included a few example shots from the internet I’d like to use as references for the type of light distribution I was after.

Clearly the type of camera used for these shots has a huge impact on the way they look, so in that you can also give me advice. Thanks Bud.

Well one thing I know for sure after reading the debate you two have going is…I want some cake!

I live in the North of England, what is this direct and ambient sunlight of which you speak?

TheSavage64 - 25 September 2012 05:47 AM

I live in the North of England, what is this direct and ambient sunlight of which you speak?

The opposite of rain