How to Align a Shared Media Texture from Linden Script

When working with Shared Media, a common issue is getting the media to visually appear as intended on the prim. This article helps solve a common problem: how to do the equivalent of pressing the texture panel Align button from Linden Script (LSL).

Using the Align Button on the Texture Panel

First, let's put a Shared Media texture on a prim the interactive way:

1. Here I've rezzed a rectangular prim:

2. I have a web page that I want to display such that the content will take up the entire surface of the prim.

This web page is "test content" - it's just a page with a 0 pixel margin that's displaying a "test pattern" image that is 300x200 pixels. This will help make it easier to see what's happening when it's rendered inworld.

HTML:

<style type="text/css">
body {
margin-left: 0px;
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
background-color: #eeeeee;
font: .8em/1.3em verdana,arial,helvetica,sans-serif;
}
</style>
<image width="300" height="200" src="test_pattern.png" />

And here's the image, in case you want it:

3. After selecting the face, entering the URL for the Shared Media, and setting the size explicitly to 300X200, the texture does not yet appear as I want it. Notice how it's squished into the corner.

4. To fix this, I click the "Align" button on the texture panel:

And voila!

How would you do this if the Shared Media was added from Linden Script?

For example, the same "Not yet aligned" problem occurs with the script that put the Shared Media on this prim:

Here's that script:

init()
{
    integer face = 2;
    integer w = 300;
    integer h = 200;
    string url = "http://www.uccellogames.com/media_demos/test_pattern.html";
   
    llClearPrimMedia(face); // forces refresh of cache if reloading the same page
    llSetPrimMediaParams(face, [
        PRIM_MEDIA_CURRENT_URL, url,
        PRIM_MEDIA_AUTO_SCALE, FALSE,
        PRIM_MEDIA_AUTO_PLAY, TRUE,
        PRIM_MEDIA_WIDTH_PIXELS, w,
        PRIM_MEDIA_HEIGHT_PIXELS, h
    ]);
}
 
default
{
    state_entry()
    {
        init();
    }
   
    on_rez(integer start_param)
    {
    }
}

There is no LSL command that does the same thing as clicking the Align button on the texture panel. Help!

Help has arrived!

Here's some LSL that has the same effect as the texture button.

doAlign(integer w, integer h, integer face)
{
    // compute scale factors based on next bigger power of 2
    integer div;
    div = 2;
    while (div < w) div*=2;    
    float scale_s = (float)w / div;
    div = 2;
    while (div < h) div*=2;
    float scale_t = (float)h / div;
   
    // compute offset from scale
    float offset_u = -(1.0 - scale_s) / 2.0;
    float offset_v = -(1.0 - scale_t) / 2.0;
 
    // do the "Align":   
    llOffsetTexture(offset_u, offset_v, face);
    llScaleTexture(scale_s, scale_t, face);
}

This LSL does the same math that the Second Life Viewer would do internally if you clicked the Align button.

And so by adding a call

   doAlign(w, h, face)

after the call to llSetPrimMediaParams, it fixes it! Hooray!

I hope this saves you the time and trouble I spent on this issue. Happy Shared Media content building.

Edelman Linden