Animated Textures – Tutorial 2

In the previous blog you saw how to use the SMOOTH option for simple animation. Although this is useful, it is also rather limited. The usual way of creating animated textures is by way of a texture which contains a set of ‘frames’, in a way very similar to that used in traditional animation.

Note: the examples from this blog are available as full-perm pre-built prims at the Templar Creations sandbox (behind the main store), for you to copy and experiment with, and use in your own builds if you wish.

Let’s have an example. Here is a texture which has three frames, to create a rotating gear:

Let’s assume you are starting from scratch. When you apply the texture to the prim, all three frames will be displayed (and will be ‘squashed’ horizontally):

This will be corrected when the animation starts running, but it is often useful to have a single frame displayed when the animation is not active. To do this for this particular texture (and any texture which has just three horizontal frames), you need to set the horizontal repeat to 0.333, so that just 1/3 of the texture is displayed. Set the horizontal offset to 0.666 to display the first frame (understanding the offsets, and how to calculate the offsets you need in order to display specific parts of a texture is an entire future blog article in itself!).

When the texture is not being animated, it will revert to this display.

To start the animation, you need a script. On the Contents tab of the Build dialog, click the New Script button, and double-click the script that appears, to edit it.

For this demonstration, the script will switch the animation on and off when the prim is clicked on, so delete the contents of the script, and replace it with the following:

[sourcecode language='cpp']
integer isRunning = FALSE;
default
{
    touch_start(integer count)
    {
        if (isRunning)
        {
            llSetTextureAnim(0, 0, 1, 1, 1, 1, 5.0);
            isRunning = FALSE;
        }
        else
        {
            llSetTextureAnim(ANIM_ON | LOOP, 0, 3, 1, 0, 3, 5.0);
            isRunning = TRUE;
        }
    }
}
[/sourcecode]

The script uses the isRunning variable to keep track of whether the animation is on or off. When someone touches the prim, if this is FALSE (the animation is not running) it starts the animation, otherwise it stops the animation.

So, what are the parameters?

The first parameter is a set of flags, which in this case switch the animation on (ANIM_ON), and set it to play continuously (LOOP). The next parameter is the side of the prim which is to be animated. Use ALL_SIDES to animate all the sides of the prim. In our example, only side 0 is animated.

The next two parameters describe the layout of the frames — how many there are horizontally (3 in this case), and how many there are vertically (1 in this case).

Suppose we had a texture which contained two vertical rows of three frames each. The frames in this texture would get displayed in the following order:

The next two parameters are the first frame, and the number of frames. This means that you can display only part of an animation if you want to. Some of the animations in the Animated Texture pack make use of this by having the very first frame as the ‘off’ frame, and displaying frames 2 to the end for the actual animation.

Note that the frames are numbered from 0, so in our three-frame example the frames are 0, 1, and 2.

The last parameter is the frame-rate — the number of frames per second.

In the previous blog post, the animation used the SMOOTH flag to scroll a single frame smoothly across the prim surface. Let’s take another look at this, because there is a little more to the SMOOTH option.

To demonstrate this, let’s have an image of 6 numbers:

Apply this texture in place of the original and replace the second llSetTextureAnim call in the script with the following:

llSetTextureAnim(ANIM_ON | SMOOTH | LOOP, 0, 6, 1, 0, 6, 0.5);

Save it, and touch the prim again to restart the animation. This time, you will see each number smoothly scroll into view.

In the next tutorial blog, I’ll show a third way of animating textures, which doesn’t make use of llSetTextureAnim() at all.