Effect of materials in object editor

What is the effect of the material selection in the object editor? Or pleaswe point tme to some place that discusses it.

Thanks

the sound of collision, the inertia, friction and wxeight if i remember

yes. rubber bounces, ya know! well, if you make a 10m rubber ball and drop it from a few thousand feet.

Oh, and light pisses everyone off.

Aside from pissing everyone off, the "light" material type causes the object to emit a glow for people who have local lighting enabled in their client settings. The color of the light emitted is the color of the prim's number 0 face.

The reason light pisses everyone off is that local lighting is insanely processor-intensive to render, and with enough objects in an area set to "light", the SL client's rendering slows to a crawl. Personally, I keep local lighting turned off in my client, because even my decent gaming rig has a hard time rendering a scene with local lighting at anything faster than slideshow pace.

A secondary effect of setting a prim to "light" is that all faces of the prim are rendered with full brightness, despite the time of day in-world. This effect also works on clients that have local lighting disabled. Sometimes people will build things with light prims specifically for this effect, typically signs or vendors, so they will always be fully visible no matter the time of day.

There is a theory that you can set a prim's 0 face color to black, and set the prim to the "light" material type, and it will be rendered at full brightness without emitting lag-inducing light. While this method does work to render the prim at full brightness, and there isn't any visible light emitted if you have local lighting enabled, there is still some debate whether or not the client is still attempting to render black-colored light. I haven't tested it myself, and I have yet to read about a definitive test that proves this method actually works to prevent lag, so your mileage may vary.

I dont think it effects weight/mass or inertia

Really does. Try making a physical object that is metal or stone, then one of plastic or rubber. You can push the lighter ones around, but not the heavier ones.

I suspect this is why when you link up prims of different material types, they all become the same type as the root prim. It would be far more complicated to calculate center of mass and angular momemtum with non-uniform density.

What can sometimes bother me about objects made of light is that they can cast light far enough to cause light pollution on neighboring parcels. This is especially irritating when large prims made of light are colored, tinting the neighborhood.

The density of a prim is always the same regardless of shape or material.
http://secondlife.com/badgeo/wakka.php?wakka=mass
http://secondlife.com/badgeo/wakka.php?wakka=material

Anyone have any more information on this? I get constant complaints of "Gee, its so dark in here...." during SL Night times. However, I've resisted the temptation to set any objects to Light to overcome this - because of my lag paranoia. This would be a great workaround if it really doesn't add any lag.

Travis

Of course, even if this trick doesn't cause lag, there's another thing to consider: aesthetics during the daytime. Yes, your build will be perfectly well-lit in darkest night if it's composed entirely of light prims, but during the daytime, it won't be shaded at all. This tends to flatten the appearance of objects and make them look considerably less realistic. The effects of shading due to the position of the sun are subtle, but very noticeable when absent.

This flattening effect can be useful, though. One interesting thing for which I've used light prims is to create a white screen upon which to take screen shots for vendors and Web stores. Because the light prims have no shading, they display as a completely uniform white surface, which allows you to take a screen shot with a totally featureless backdrop. I've also seen this done with bright green or magenta instead of white, both decent colors for easy removal in Photoshop or your image editing program of choice (usually with the "magic wand" tool or its local equivalent). However, if you use something other than white, you probably want to turn off local lighting on your client before taking screen shots; colored light will radically tint the coloring of your avatar, which might not be the best way to show off your clothing, attachments, or other screen shot-worthy items.

That said, my photography studio built from light prims is in orbit at about 500 meters, generally well out of visible range from the ground, so it doesn't cause any light lag for people visiting my home.

Are there other lag issues related to material type besides light? For example, glass and water.

The fact that light is bundled with the other materials is an unfortunate coincidence.
Lights, in general, add load to any rendering engine.
The other materials have no effect on rendering.
The trick referred to above seems to be true.
http://secondlife.com/badgeo/wakka.php?wakka=light

The reason for my asking is my recollection of a post from the owner of a spa suggesting that she reduced the excessive lag experienced there by minimizing water usage. Is light tied to water? Are there ways of using water that are more lag efficient? Is it the transluscency and reflective qualities which would be shared by glass?

The material type "glass" has no effect on transparency. But alpha and transparent textures that are often used for glass and water can really lag a client. I've been told that is because it requires an expensive z-sorting step, which makes sense. Animated alpha/trans textures in particular seem to overwhelm my system, so waterfalls are brutal on it.

It's unfortunate, but usually the better something looks in SL, the slower it's going to be to render.

There is an interesting idea. Projecting black light. LOL

And I don't mean ultraviolet.

Only when dealing with pigments/paints can black can be considered a color.

But when dealing with light, black is the absence of color.