Daily Archives: January 24, 2013

Race Mark Rez

buoys

Noodle asked: “It is kinda hard to call a layline, when the buoys aren’t visible beyond 64 meters. Any idea why it is so? Do they simply need to be bigger for SL to display them properly?”

It’s pretty frustrating to sail a race course and not see the mark buoys until you’re practically on top of them. Sailors often use landmark HUDs like TRAPNAV to get around the problem (Thank you Trapeze!).

I certainly don’t pretend to know the algorithm SL uses to prioritize the order of objects as they rez in the viewer, but I suspect you are right; size matters. I remember that several of us looked into this issue back in 2007 when it was a major problem for the Starboards Yacht Club races. Since the issue is coming up again for many sailors (including me), I ran around and did a few backyard tests on it today. 🙂

view angleI tried to figure out the distance at which each of the  three buoys on the Linkous hotlaps course first appeared.

I normally use the Firestorm viewer. For all images below, I set the draw distance at 1024m and all graphics at median settings. I then emptied cache and teleported to Henker, the sim next to Trulan, where there’s a centrally-located yellow buoy.

From Henker I looked into Trulan and saw… nothing. As shown below, if you are 150m away from a buoy (and across 1 sim line), the buoy never rezzes, even with dd=1024.

If you move closer to the buoy, it suddenly appears when you are within 130m. The same thing happens with the other two buoys there; they first rez at distance of 130 m (which is across a sim line in each case).

buoys rez at 130m

To make sure this was a server-side effect, I repeated the measurements using a different viewer. The Singularity viewer features ‘draw-distance stepping‘ (that’s why Orca likes it 🙂 ). When you move to a new view region, Singularity prioritizes the objects closest to you so they rez first.

How does it do that? Easy. If you set your dd=1024, when you go to a new area Singularity throttles that dd back to a much shorter view distance in order to speed up the local rez. It then gradually returns the DD back to your preset numbers.

If you open up the map after you teleport, you can watch the draw distance in Singularity graphically expand during the first minute or two. Here’s an example:

singular vision

Using this viewer, the three buoys in Zindra all rezzed at a distance of 130 m, as they had in Firestorm. That’s no surprise; Singularity doesn’t actually change rez priority, it just sort of ‘modulates’ what you asked the viewer to do. The 130m rez limit for the buoys I looked at was apparently a server decision.

So how does the server-side algorithm decide what distance to rez something? Well, a big factor seems to be object size (meaning linear dimensions, not ‘prim count‘). To demonstrate that, I rezzed a 20x15x24m one prim box in the air over the buoy in Trulan. I then logged out, emptied cache, and came back over 256m away from the target. When I did that, the box popped into view immediately, even though I still could not see the much smaller race buoy beneath it.

256m boxThis evidence supports a fix that many sailors and estate owners are very familiar with, and have used for a long time.

buoy base

If you want a race mark to rez early, you somehow need to make it look ‘bigger’ without messing up the craftsmanship or authentic appearance of the buoy.

Probably the simplest way to do that is to attach a large, single-prim underwater extension to the buoy, as shown in the pic on the right. This simple adjustment also makes the mark more visible on the map and mini-map.

I’m pretty sure this fix also works if the large underwater object is phantom and transparent, but I haven’t tried that out yet under the current server versions, and there are reasons to think it might not work with the recent changes. We’ll see. 🙂

I also know there are probably more elegant ways to fix the buoy-rez problem, but please remember this is Jane talking here. I don’t tend to do ‘elegant‘ well. 🙂

Anyway, here’s the bottom-line result, included below. The top picture shows the yellow nav buoy in Trulan. It’s very pretty and nicely scripted by RJ Kikuchiyo, and it has multiple user- controlled options (ask your local SL Coast Guard for a box of them). 🙂

The lower picture shows the effect of the underwater attachment. You can now see that buoy two sims away and at a distance of over 400 m.

over 400m distance