Class Summary

Class 6: Flexible Prims


Flexible prims are prims that… are flexible That is, they can move and interact with the environment around them – Wind, Gravity, Tension, Force.

For example, a flag waving in the wind, long hair that moves around as you move your head, a skirt or scarf that moves in the wind, curtains, a tablecloth, flowers, tree and plants - these are all examples of Flexible prims.

Adding the Flex to Flexi-prims

So far, we have been working with regular prims that have no special features. The position arrows intersect a regular prim through its centre and it behaves in a predicable manner in relation to the SL environment.

Regular Prim

To make this normal prim flexible, we tick the Flexible Path box that is located in the Features Tab on the Edit window.

Features Tab

There you go - one click and you are done! Your prim is now Flexible.

Have a look at your new Flexi-prim. Not much has changed?

Click on one of the red, green or blue position arrows and move your prim.

What do you see now?

Wobbling Flexi Prim

Another indicator of the changes to your prim are the position arrows. They normally intersect a prim through its centre, but for a Flexi-Prim, the position arrows intersect at the bottom of the selected prim.

Flexible Path setting in Features Tab

This bottom edge of the prim is the anchor for the prim; the rest of the prim will flex from this anchor point. Of course, if you want your prim to hang downwards, rotate the prim 180 degrees so the anchor is located at the top.

By default, Flexi-prims are phantom objects, that means that they do not collide with solid objects - they pass right through them. You can see this phantom behaviour with Flexi skirts and Flexi hair as they move around and through the avatars wearing them, the chairs they are sitting on or even other people that touch or collide with the phantom prim.

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Which Prims can Flex?

Not all prims can be made Flexible. If the Flexible Path option is greyed out in the Features Tab, that means the prim cannot become a Flexi Prim.

My general rule is that the prims in the first row of the Edit window can be made into Flexi-prims, and not the prims in the second row.

Flexible Prims Non-Flexible Prims
Box Torus
Prism Ring
Cylinder Tube
Sphere Sculpties

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Flexible Options

Let's have a close look at all the Flexible settings in the Features Tab and experiment on our prim.

The image below shows the Flexible Path options and their default settings. As you can see, there are quite a few settings that we can adjust to change how our Flexi-prim behaves.

Flexi Settings in the Features Tab


The Softness setting lets you set how much bend your Flexi prim will have. The default is 2.000 and settings can range from 0.000 to 3.000

A low Softness setting of 0.000 means that there will not be much flex to your prim - only bending at the bottom and not for the rest of the prim. the highest setting of 3 means you prim will flex like a wet noodle

It has been noted in another blog that a Softness setting of 3.000 requires extra processing for your computer and to anyone around who's computer is looking at your Flexi-prim. So I guess, use it sparingly, and take advantage of the other settings to create the soft Flexi effect you want.

Softness settings

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The Gravity setting lets you choose how much your Flexi-prim will be pulled downwards by Gravity.

The default setting is 0.300 and setting options range from -10.000 to 10.000.

The positive numbers pull your prim downwards towards the ground.

The highest setting of 10.000 means that the full forces of gravity are working on your prim. When you move your prim, it will revert to the downwards pointing direction very quickly.

The negative numbers are a sort of an anti-gravity setting, allowing your Flexi-prim to point upwards, away from the ground and into the sky.

The zero value applies neutral gravity forces to your prim, it is neither pulled down by gravity nor floats up by anti-gravity.

Gravity settings

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The Drag setting controls how much resistance an object has to movement.

The setting options range from 0 to 10 and the default value is 2.000.

Low drag numbers let the prim bounce around easily and without resistance as it moves back into its original position.

A high drag value like 10.000 will make your prim move more sluggishly as it slowly returns back to its original position, like pulling through water.

Have you seen those Flexi skirts that take forever to gently fall to the ground? They have a high Drag setting, err... when SL is not causing lag!

Flexi Settings in the Features Tab Flexi Settings in the Features Tab

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Wind is a cool setting :) It determines how much the environmental wind in Second Life affects the Flexi prim. Yep, there's a wind that constantly blows through SL. It changes direction all the time. And the strength of the wind varies as well. And oh BTW, the SL wind goes right through walls (so its blowing indoors as well :P).

The Wind setting gives your Flexi prim a natural movement. This is great for hair. It's especially important for stationary Flexi prims, like flags or ribbons; otherwise, stationary Flexi prims won't move at all.

The Wind setting can range from 0 to 10.

A setting of 0 means the SL wind has no effects on the Flexi prim.

A setting of 10 means the Flexi prim will flap wildly to the slightest SL wind. It will also be very sensitive to direction changes in the SL wind. Great for things like ribbons :)

Flexi Settings in the Features Tab Flexi Settings in the Features Tab

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Tension determines how stiff the Flexi prim is and how quickly it will spring back to its original position when moved.

Tension settings range from 0.000 to 10.000 and the default is 1.000

A setting of 0 means there is no tension and the prim will fall down and stay there.

A setting of 10 means a very stiff Flexi prim. It will act almost like a spring, and will try to maintain its shape by snapping back quickly into position when moved.

Flexi Settings in the Features Tab Flexi Settings in the Features Tab

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Force X, Y, Z

The X, Y, and Z settings gives a push in the respective direction. The settings can be -10 to 10, so it could be a positive or negative push (or pull, so to speak).

For stationary Flexi prims (like Flexi prims on buildings), these might be useful in creating an effect. For example, you can use the X setting to make a flag point towards the east, unless there's a very strong wind in another direction.

Note that these settings are always relative to the sim. So, if you add a setting to the Y Force of your Flexi skirt prim, then it would always want to point and flex towards the West....

The Z setting is almost identical to Gravity (so you might as well use Gravity).

Flexi Settings in the Features Tab Flexi Settings in the Features Tab

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Wrap Up

As you have seen from this brief overview of the Flexible settings, you have a lot of scope to add some interesting Flexible features to your prims.

Common uses for Flexi Prims include skirts, hair, trees and plants, flags, ribbons, curtains.

I am sure there are many, MANY other examples that you can use in your own builds.

Click on the image link below to go to the Flexi-Flag project page where you can practice making some Flexible Prims for your flag and flagpole.

Flagpole with Flexi Flag

Next Class: Class 7: Let There Be Light

Previous Class: Class 5: Transparent Prims

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