PAGE 5

SEEING THE LIGHT

realistic sunstrength 300There are a number of other settings we can use on the light control page. Click the tab Direct Sunlight and there are two basic options - Specify Sunlight Colour and Realistic Sunlight Penetration System. So far I have used the Realistic Sunlight Penetration System, with the default settings. With most images I find that to give the most realistic rendering of the light. The picture on the left was generated with those settings, and will act as a control so that you can see the difference made by other settings.

In the picture on the right, the only change I have made is to increase the sunlight strength from the default 150% to 300%. Everything in the picture is lighter - sky, water and grass - except the shadows which are a little darker. But the overall quality is not so good. There is very little detail in the snow, and the mountains have become almost a white blob. This setting is not suited to a snow scene, but you can see that the water has in fact improved. If there were not so much snow around, the stronger sunlight might very well have enhanced the picture.

realistic sunspecifyIn this pair of pictures, as in all on this page, the control picture is on the left. On the right I have returned to 150% sunlight, but changed to Specify Sunlight colour. The differences are rather subtle and difficult to see in these small previews, but there is a little less realism in that the shadows and highlights have less shades of colour in them. If you look very closely at the shadows in the bottom right corner you can see that they appear a little darker because the reflections within the shadow are not rendered so well.

You can change the colour of the sunlight, to give more dramatic or unusual effects, but the default colour is appropriate for most natural scenes. To change it, click on the Colour of Sunlight button and move the sliders in the dialogue box which appears, till the colour you want appears in the sample box. Be sure to note the default settings, because although the Reset button will reset the strength of sunlight to the default 150%, it will not reset the colours.

Returning to the Realistic Sunlight Penetration setting, the Effect of Atmosphere setting would have little effect on a scene such as the one we have here, but it is very useful if you have a scene involving mist. I will come back to this option when we are looking at the atmosphere settings.

realistic suncloud coverIn the picture on the right I have changed Percent of Cloud Cover to 100%. This has the effect of the sky having become overcast and the scene becoming flat and dark. The sky itself is unchanged, and the visible cloud cover is not increased. The clouds actually seen in the image have to be set from the cloud generator.

70% cloudThe default setting for this option - Percent of Cloud Cover - is 20%. At settings below 100% the difference between shadow and sunlit zones is varied in a natural way, as though the sun were shining through hazy cloud. At about 70% the sunlight is weaker, and the shadows lighter. The snow is not such a bright white, but you can still see detail in both sunlit and shady areas, though the contrast between them is not so great.

The effect is more convincing if cloud cover is increased, using the cloud generator, because the very bright blue sky with few clouds does not suggest the hazy sun which would be casting these shadows.

realistic sunmulti-directThe last option on this tab is multi-directional shadow lighting. This introduces more colours into the shadows and allows for the bouncing of light within the shadow. It gives a more natural effect. The effect is particularly noticeable in the clouds in the sky, which have more subtle shades than with the single colour shadow.

The shadows are also lightened in this mode, because parts of the shadows receive light bouncing from objects within the shadow area.

darker shadowsBecause of the lighter shadows, it can be useful to darken them slightly with the shadow lightness slider. For the example on the right I took the slider to about 38%. I then saved the world setting again, to preserve the multi-directional shadow lighting and the shadow lightness setting. This will be the starting point for working on the picture from now on.

In most of these options it is possible to change the colour of the sunlight, and of the shadows. This can be useful for special effects, but for rendering of natural scenes I have never found settings which improve on the defaults.

scene 5

For the rest of the options in the Lighting Controller I am going to leave the picture I am building during this tutorial and use an image of just sea and sky, because all of the remaining options are more easily understood with the sun in the picture.

default suncorona 0For the first tab, Sun's appearance, I am also using a cloudless sky. On the left is the way the sun looks at the default settings. You can just see the disc of the sun within a wide corona. On the right is the result of setting the corona size to 0. With a full daytime sun like this, the difference is not great, but in a sunset scene the disc of the sun becomes much more distinct when the corona is removed. We shall be looking at sunset scenes in the next section, on atmosphere, and we will study these settings again in conjunction with the atmosphere settings which give the red and gold sunset skies.

In the picture below I have lowered the sun to just above the horizon and reduced the disc size to .5 of a degree. You can already see that this has begun to affect the colouring and there is already a hint of sunset there, but these settings alone will not produce a sunset without some atmosphere settings being changed.

low sun half disc

default glowglow amount maxFor the final tab on this control, Lighting of Atmosphere, I have reset the sun's appearance to the default settings, and the picture on the left shows the default settings for glow - the feature which causes the clouds, mist and so on, which are near or in front of the sun, to glare showing that the sun is there. The picture on the right shows glow amount raised to the maximum. The sun's glare is now so wide that there is very little blue left in the sky.

glow power maxamount & power maxIn the scene on the left I have reset the glow amount to the default, and set the glow power to maximum. The glare is much brighter than in the picture above, but there is still blue in the sky and the spread of the glare is more controlled than in above right

In the picture on the right, both power and amount are at maximum. The sun's glare completely fills the sky and there is no blue showing at all. In fact this setting is so extreme that the glare hardly looks like glare at all, and has the appearance of an overcast sky, were it not for the bright reflection in the sea. Under an overcast sky the sea would be leaden.

Obviously there are a huge number of combinations of glow amount and power, between the extremes, which you can juggle to get the appearance you want. There is little point in using Sun's Appearance or Lighting of atmosphere unless the sun is at least partially visible in your picture, or only just out of the picture so that the glow is visible.

In the next section we shall begin to study the effects of the atmosphere settings, on their own or in combination with other settings.

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