Prim floating text fades prematurely over distance from camera

Environment

Second Life Release 7.1.11.12363455226 (64bit)
Release Notes

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Second Life Preflight 2025-01-17.12835327626
Release Notes

CPU: Apple M1 Pro (2400 MHz)
Memory: 16384 MB
OS Version: macOS 15.3.0 Darwin 24.3.0 Darwin Kernel Version 24.3.0: Thu Jan 2 20:24:16 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6000 x86_64
Graphics Card Vendor: Apple
Graphics Card: Apple M1 Pro

OpenGL Version: 4.1 Metal - 89.3

Window size: 1174x752
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February 20 2025 16:22:27

Description

Floating text on prims fades at a much shorter distance than the PrimTextMaxDrawDistance parameter would suggest. It appears that some 2nd, undocumented parameter is causing text to fade at 16m distance, even when PrimTextMaxDrawDistance is set to a large value.

In some cases (like for server testing), it would be valuable to allow higher-than-default values of PrimTextMaxDrawDistance to allow the user to see floating text at great distances, but this is currently not possible.

Reproduction steps

Repro:

1. Login, and set the PrimTextMaxDrawDistance debug setting to its default value of 64m
2. Rez a box and put the 'floating text test' script in it (shown below)
3. Sit on the box and note the opacity of the 'camera distance' floating text above the object as you move your camera nearer or further from the object
4. Set PrimTextMaxDrawDistance = 10 and repeat step (3)
5. Set PrimTextMaxDrawDistance = 300 (any higher is clamped by the viewer) and repeat step (3)

Expected results:

• With PrimTextMaxDrawDistance = 64, I expect floating text to become invisible when the object is >64m from the viewer camera position. At least that's what https://github.com/secondlife/jira-archive/issues/11995 seems to suggest.
• Similarly, text should fade out around 10m when PrimTextMaxDrawDistance=10, or 300m when PrimTextMaxDrawDistance=300

Actual results:

• With PrimTextMaxDrawDistance = 64, prim floating text starts to fade at around 12m distance, and is fully transparent at 16m
• Setting PrimTextMaxDrawDistance to a smaller value like 10 causes floating text to toggle be either fully opaque or fully invisible at 11-12m distance (it's not 100% consistent)
• Setting PrimTextMaxDrawDistance to its maximum value of 300 causes no change in behavior compared to the default of 64 - text is still invisible beyond 64m

// When an avatar is seated on the object, set floating text to indicate camera distance from object

default
{
    state_entry()
    {
        llSitTarget(<0,0,1>, ZERO_ROTATION);
        llSetScale(<2,2,2>); // so it's visible from afar
        llSetTimerEvent(0.5);
    }
    
    changed(integer change)
    {
        if(change & CHANGED_LINK && llAvatarOnSitTarget() != NULL_KEY)
        {
            llRequestPermissions(llAvatarOnSitTarget(), PERMISSION_TRACK_CAMERA);
        }
    }
    
    timer()
    {
        key a = llAvatarOnSitTarget();
        if(a != NULL_KEY) llSetText((string)a + " camera distance: "
            + (string)llVecDist(llGetCameraPos(), llGetPos()), <1,1,1>, 1);
        else llSetText("Nobody seated.", <1,1,1>, 1);
    }
}

Start by reproducing the issue with the PrimTextMaxDrawDistance setting and the supplied floating-text test script, comparing values of 10, 64, and 300. Trace the viewer's prim floating-text rendering and distance-fade behavior. Done means text fades at the configured distance, including values above the default, without the reported 16m limit.