Falling Feathers Part Two: Particle Systems (Basic)

Today we’re going to be looking at particle systems in order to make our feathers fall from the sky.  I maintain that they’re not falling because of an exploding bird, however if you want to believe that then go right ahead! (Possibly you could even add guts and blood in that case)  Quite a long post, it took me two and a half hours to write the first draft, so here’s a friendly warning to say not to expect this to be a quick reading.

This post was almost delayed.  Just by a week, or two, or three… you get the idea.  The reason for this is that I’ve discovered a flaw with using the feather we created last week as our falling feathers;  Because we used ‘Hair and Fur’ to create it, you can’t directly add the feather to a particle system.  After asking around on a couple of forums, someone (fongmingyun from CG Hubs http://fongmingyun.cghub.com/) was kind enough to point out the obvious step I was missing.  You would need to convert the ‘Hair’ to splines or a mesh in order to attach it to the feather properly and make them fall.

I tested this out yesterday; it works.  However we’re going to create a much more basic feather object instead because the amount of lag created just by turning them into splines was incredible (not to mention what happened when I tried to add it to a particle system, I’m actually very truly grateful that my computer didn’t blow up).  We’ll still use the feather we created last week when we tie the image together, but for the moment we’re going to hide it from our scene and ignore it.

What is a Particle System?

Particle systems within Max allow you to achieve different effects; explosions, fire, fountains, waterfalls, snow, other things falling from the sky, or even things swirling in to create another object or word (to name a few).  This is one of my favourite parts of using 3D, but it’s also one of the more technically complicated parts.

The idea is to use a system to tell the computer to move objects in a way that you dictate.  It’s easy to create something very quickly using the presets, however making a specific effect is a great deal harder as there are so many variables to tweak and keep track of.  That said, it sure beats animating every feather and will probably look more realistic too.

Preparation

As I mentioned in the introduction, the first thing we’re going to do for this tutorial is create a very simple feather model without using hair and fur.  Just hide our other feather for the moment (or hide the layer its on, if you use layers.  Don’t worry if you don’t, I’ll probably discuss them after we’re finished with the feathers project) so that we have a clear scene to work with.

Very quickly take a cube with 3 segments for height, 6 for width, and 1 for length and name it ‘feather_particle’ (or whatever you want to call it, so long as it’s named).  Convert it to an editable poly and Extrude 5 polys on either side of your new feather (one side at a time).  Move them up towards the top, then select the top vertices and move them up until it makes a curved shape.

Once you’ve done that, select the lower vertices where your extrusion joins the rest of the model and move them down.  Select the tips of your extruded surface and move them closer together, then move them up so that your feather curves from the centre.  Apply a turbosmooth modifier and you should have something that looks like our rendered image.

The Process

Now that that’s out of the way and we have something we can use as a particle, go to the creation tab and open the drop down.  We want to select ‘Particle Systems’; this will give you this menu:

From here we want to select ‘PF Source’ and draw it in the top viewport.  After you’ve drawn it, just move it up along the Z axis until it’s a little above the gridline.

At this point we could tweak parameters in the ‘Modify’ tab (red on the image), but instead we’re going to open up the ‘Particle View’ menu.  You can do this by pressing ‘6’ on your keyboard, or by going to ‘Graph Editors’ and selecting it from the dropdown.  It’ll bring up another window within Max which you can move around and resize until you find a comfortable place for it (I tend to leave mine fairly large and move it to the side away from my perspective view).

This view can be a little daunting at first if you’ve never really looked at it before, but once you get used to what some of the functions do you’ll feel a lot more comfortable with it (like anything else really).

Since I’ve used Max to create particles before, we’re going to run through some of the basic settings for my machine to make sure they match yours so we can prevent widely different effects.  I’m not going to go into too much detail on these, just have a look through the following images and check the numbers are the same.  Where an explanation is needed it’ll be on the image.

Now that we’re on the same page with our starting settings, select ‘Birth’ in the ‘Event 01’ object.  This part controls how many particles are created throughout your animation, and how long (in frames) they continue to be created.  There are two options in here that determine how the computer calculates this; ‘Amount’ and ‘Rate’.  Using Amount means that for the time period you define, you’ll create only this many particles and no more.  Rate, on the other hand, continues to create particles at a rate (hence the name) you determine for the entire time period you’ve defined (each second/30 frames it’ll produce the number).  Because we only want a simple effect, we’re going to use ‘Amount’ for this tutorial; lets set it to 20 for now.

If you move the time slider along you can see that the particles don’t start to fall until the very start of the animation, and stop appearing at frame 30 after only one second.  Sometimes this is the sort of effect you want, however we’re going to change it.  To do this we need to look at the values for ‘Emit Start’ and ‘Emit Stop’.  Because we want the particles to have already started falling by the time the animation starts, we can change the ‘Emit Start’ property to -10 – or any other negative, but since we’re using ‘Amount’ -10 is far enough back to start it without using up our entire feather quota.

Instantly you can see a change in the viewport; even if the time slider is sitting at frame 0, the feathers have already moved from their starting position.  This is exactly what we want.  Now we need to fix the ‘Emit Stop’ property because one second of animation is far too quick for the light, happy mood we want to create.  Lets set it for 75 frames (2 ½ seconds) to create a nice slow particle birth.  Have a quick look at the preview animation inside Max to see if you like the effect as it stands; if not you can always tweak it after the tutorial is finished to suit your own tastes.

The particles are still moving too fast for something as light an airy as a feather, so click onto the ‘Speed’ parameter and we’ll fix that just now.  In the drop-down for Direction make sure that you have ‘Along Icon Arrow’ selected; Direction determines how the particles move out from the particle emitter (the thing you can see in your viewport).  Its worth playing with the other options to see what they do, but for our needs the default is fine.

The Speed parameter (you guessed it) determines how fast the particles fall, and Variation determines how much of a difference from this value the particles are allowed.  Right now they’re set at 300 and 0; we want the speed to be much lower.  To speed things along a little I experimented with the values myself starting at 50 and ending up far lower than I expected at 30.0.  I may tweak this again later but for now set it to 30, and leave the variation at 0.

Now we need to delete ‘Shape 01’ from our Event; it would create the particles as cubes like the render below if we left it in, whereas we’d like to use our own geometry. Once it’s deleted the particles themselves will have no shape if you render; it’s meant to be this way, no need to panic!

From the menu below click and drag ‘Shape Instance’ into ‘Event 01’ just above Display.

In the menu it shows you, click on the button under ‘Particle Geometry Object’ and select your feather.  The button should change to show the name of your object, and the shape of your particles will be the same as your feather.

At the moment, all the feathers will be the same size as your original feather (and possibly too big).  To fix this we need to change the parameters in ‘Scale %’ and ‘Variation %’.  They’re pretty self explanatory; Scale changes the size of your object when it’s in the particle system, and Variation allows the feathers to be different sizes based on a percentage (the number you set defines how far above and below your scale percentage the particles’ size can be).

Before you start, go to ‘Display’ and select ‘Geometry’ from the dropdown menu.  That’ll let you see all the particles as they’ll appear in your render.

Since everyone will have modeled a different sized feather, you’ll need to play around with the scale to find what the right size for your normal feathers will be.  After that we’ll set the Variation to 5% to allow for a little difference but nothing too major and unbelievable.

It’s now nearly the effect we’re looking for; the feathers are falling at the right speed, there’s enough of them, and we can see that they’re the right shape.  There are now only three more problems with our animation; Rotation, Fall Type and Length.  Real feathers don’t fall straight down, they loop and twist and spiral and seem like they’re floating.  They also don’t suddenly stop falling at a certain point in midair unless they collide with something.

To fix this, we’re going to look at ‘Rotation 01’ within our event first.  Change the dropdown under ‘Orientation Matrix’ to ‘Speed Space’.  The ‘Rotation’ parameters determine the way the particles are initially rotated; for this example I’ve changed the values to 50, 80, and 40 for x, y, and z respectively.  The most important parameter on this screen is Divergence; this determines the random aspect of the starting positions.  I’ve set this to 120, but you can play around with this setting to find something more suitable for your feathers.

From the bottom menu again, click and drag ‘Spin’ into your Event.  This is what will control the rotation of the particles as they fall.  For the dropdown under ‘Spin axis’ select ‘World Space’.  Watching a preview will show you crazily spiraling feathers that look more like those funny little seed pods from Sycamore trees.

Under ‘Spin Rate’ the value is 360; presumably this represents the maximum angle of the spin.  Play around with the values and see what seems right for you; I set mine to 40, and it might still be too fast.

The other values you need to play with are the X, Y, and Z amounts in the ‘Spin Axis’ section of the menu.  Each value has a maximum of 1.0, and a minimum of -1.0.  This part is really just a case of finding out what looks best to you; my values are 0.5, 0.5 and 1.0.

The last thing we’re going to change today is the length of the animation itself; this will let the particles fall further and seem much more natural.  Once we’ve changed this you might also want to change the ‘Birth’ values for ‘Emit Start’, ‘Emit Stop’ and ‘Value’, because it will change the balance of the animation.

To do this, we need to click on the ‘Time Configuration’ button down at the bottom.

We’re going to ignore 9/10s of the information in that menu and change the ‘Length’ value to 300.  That will give us 10 seconds of animation, which should be enough time to get a feel for what we’re doing.

I’ve just adjusted my Birth values slightly so that ‘Emit Stop’ is at 200, just to give it a much more serene, floating look.  I also changed the Amount to 10, so that there was less clutter.

That’s it for this week – next Wednesday we’ll look at adding a background, textures and making the feathers drift.  Here’s a quick render of my animation to let you see what things look like at the moment; we’ve still got a little bit to go before we’re fully finished.

Final Preview

Conclusion

This was just a basic introduction to some of the particle effects you can use, initially I’d intended to go over a few of the other presets as well (exploding feathers could have been fun) but I decided to keep it fairly simple for now.  You could write entire books on how to use particle systems in 3Ds Max since there’s so much you can do with them.

Over the next two weeks we’ll be looking at how to change our feathers (including the one we made last week) into a compelling scene with lights, textures, some minor dynamic forces (we’ll get to those), and camera effects.  At the end of it we’ll have either a still image, or a short animation, dependent on your preferences.  As always, the methods here aren’t the only ways to create this effect – I’m still learning too!

If you’ve any suggestions, comments, or questions feel free to reply here (or by email if you’d prefer) and I’ll be happy to incorporate/answer them.  Hope you’re enjoying this as much as I am – See you Friday!

———-

Part One: Hair and Fur Effect

Part Two: Particle Systems (Basic)

Part Three: Setting the Scene

Part Four: [due 3rd Feb]

Part Five: [due 10th Feb]

Heather, the owner, started Shades of a Dream in January 2010 to help you fill gaps and increase your knowledge in 3D and Visual Effects. She also runs a newsletter; want a little extra punch? Sign up here

Heather Craik

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