Second Life Prim Lights – 3

Full-bright and Glow

This is the last article in my short (and rather infrequent) series about lights in Second Life. I’m going to take a look at two elements of textures which are often used in conjunction with lights, and which are also widely misunderstood and misused.

Let’s start with Full-bright. This can be switched on or off on the Texture tab of the Build dialog, and applies to the currently selected texture, or to all the textures on the currently selected object if you haven’t selected an  individual face.

What does it actually do? The most obvious effect is that during SL ‘night’ the texture will appear bright (as the name of the option suggests). During daylight the effect is, predictably, less obvious. In fact, sometimes the object might actually appear to be darker in daylight.

Here is the same scene in both day and night. The picture on the wall has full-bright set on it, and you can probably see that the picture is displayed identically in both light settings.

Let’s step back a moment. How does Second Life create the ‘night-time’ effect? Well, apart from changing the sky, it obviously makes all the objects in the world darker. It does this by taking the colour which they should be, and blending it with the ‘nighttime’ colours.

What might be less obvious, is that it does something similar during daylight. It takes the colours, and adjusts them according to the current lighting. This is how you get the distinctive orange lighting effect at sunset that some people  complained about when Windlight was first released.

When you set a texture to full-bright, this blending is switched off for that texture, so it always displayed at it’s actual colour, regardless of the current lighting. At night, this has the effect of making the object seem to light up — in fact, it is simply not being darkened.

So much for full-bright. Now what about its companion, Glow? Unlike full-bright, this is exactly what it says. When you set a glow value for an object, it acquires a glowing halo around it. This can range from a subtle, barely visible aura, up to a near-blinding glare.

Transparency tends to lessen the effect of glow slightly (the lower row in the picture has transparency applied).

Under most circumstances, using low values is best, usually no more than about 0.25, and often less than that.

One thing to be aware of is that if two glowing objects overlap in the viewer, the glow effect is doubled. This is not always what you want to happen, so you probably need to be careful if you place glowing objects close together.

Another unfortunate effect that I’ve often seen is where the glow is being used with an object which has a partially-transparent texture. For the glow to show up in this case it needs to be set quite high. When the texture is fully loaded, the effect is subtle and often beautiful. Unfortunately, while the texture is still being loaded, the glow is in full force, and often overwhelmingly bright. There is not much that can be done about this, but if you intend to use this kind of effect, you should be aware of this pitfall.

Glow and full-bright work very effectively together when creating a light. As a simple example, rez a prim, set its transparency to 25 (if you set it too high you will lose some of the effect), then switch full-bright on and set the glow to 0.2. The result will, of course, not actually illumine the surroundings unless you set the Light feature on, but this kind of ‘fake light’ can give the illusion of there being more lights than SL actually supports, especially if you use several of these in conjunction with a single ‘real’ light.

Some SL photographers make use of a interesting effect which happens when an avatar stands in front of a ‘glowing’ texture. This is easier to show than to describe, although the effect is quite subtle, and is caused by the glow slightly spilling over the edges of anything in front of it. Here are ‘without’ and ‘with’ glow versions (this is a rather exaggerated version, with the glow set quite high to make the effect obvious):

However, if you intend to save your photos, there is an issue to be aware of, which is that the Second Life snapshots tend not to capture glow correctly. For example, the scene of streetlights on a wall (above) was captured using my computer’s screen-capture, rather than the Second Life screenshot, which looked like this:

Finally, ‘glow’ works best when it is used for subtle effect, and with some restraint. Whatever you do with ‘glow’, please don’t do this: