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In this section we'll be dealing a lot with Lifespan expressions, but to best show that I am going to set up an emitter and put some colors on the particles as well. So the first thing we're going to do is under Particles, we are going to create an emitter. And I am going to make a Directional emitter. I am going to call it part. Under Distance/Direction Attributes, I am going to give it a Direction of X and I am going to give it a bit of a Spread so that they don't go in a straight line, they are little spread out. Let's see if that's enough. You want to go Apply. I am going to make my scene about 600 frames long. Here is my emitter sitting right in the center.
Let's go and there are the particles coming out along the X-axis because that's the direction, the X-axis. I am going to go into the particleShape node, into the Attribute Editor of it. And I am going to change the Particle Type to Clouds, particleShape1 from Points to Clouds. And that's a bit of a big radius, so I hit the button that says Current Render Type right under the Render Attributes, Particle Render Type and I am going to add just kind of an overall Radius, for all of the particles I will make them around about .3. That looks kind of okay to start.
The next thing I am going to do is I want to disassociate the color from the shader ball. So I am going to open up my Hypershade, bring it up, make a new particleCloud, assign it to the particles, click on it. Under Color, I am going to hit the Map button, then go up to the Utilities again. And I am going to go under Particle Utilities, I am going to hit the Particle Sampler button and once again the color is now disassociated from the shader ball.
And the particle color will be ruled by the color expression, which I don't have yet. So I am going to hit the Color button and we are going to add a Per Particle Attribute. Add Attribute. I am going click right in here. This time I am going to not make an expression. I am just going to create a ramp. Now I am going to edit that ramp and you are going to see that this is where Lifespan comes into play for a ramp and for the color on a ramp. When a particle is born, it's start at the bottom of the ramp and as it lives it travels up through the top of the ramp. So for a particle's life when it's first born in this ramp it would be red and then as it lives it will be blue for the duration.
Now if all the particles live the same amount of time, they will all look similar as they travel up through there. So I am going to go once again back into the particleShape1 there. And I am going to also show you that there is a Lifespan Attribute right up here. Right now the Lifespan Mode is Constant and the Lifespan says its 1. Basically each particle is only going to be living for 1 second or 24 frames. So Lifespan 1 means 24 frames. If I made it Lifespan 10 right now, Constant, then all the frames will be living the same amount. They'll all be living for 240 frames before they die off. And you can see them dying off after 240 frames.
And so let's see what the color looks like now. And you can see the particles start out just red as they are born and as a particle ages it goes and turns into blue because that's how our ramp is set up from Red to Green to Blue. Let's go back into our ramp. Let's edit the ramp, make it slightly more interesting. Let's start them out maybe as more of a yellow hot, make them closer to black. And then kind of in the middle, we'll make them red a little bit like that. So it's kind of a little bit more of a fiery look to these things as they go.
And you can see what will happen there. I am going to add in one blue stripe in the middle of this just so we can have something to look at that will help us see what's happening. Put a little blue right in there, which is weird but... Okay. And there is that blue stripe for the particle color. Now the next thing we want to do once again is I want to go into the Attribute Editor of the particles and I want to instead, I want to put an expression here because I don't want all the particles to live the same amount of time.
I want them to vary how long they are going to live. But one of the first things I have to do for that is I have to change the Lifespan Mode from Constant to lifespanPP. Then I have to go down here and in the Lifespan PP I have to put an expression. I am just going to put in a Creation Expression. And I take that, Ctrl+C, add it here, Ctrl+V. And let's make the particles equals a random expression, 1 and 12. And let's see what that looks like.
So this would mean that the particles are going to live anywhere between 1, which would be 24 frames, and 12, which would 12 times 24 frames. So let's say we'll do a little fast render of this, get them going for a while and see what that looks like. And you can see that the particle color is starting to be mixed up because different particles are living different amounts of time. So they are going through their lifespan faster. Let's go and change the ramp even more, so it's even more apparent when we are talking about that. So I am going to put a little something here, a little green maybe right there. Oh! She is pushing the wrong thing, right here, like that green. And then make it really obvious, I am going to put something there.
I am going to make that purple and then I will make that purple. Let's see what happens. I am really hopeful the colors will be more mixed up now. So you can see how varied and mixed up the colors are because they are going through their lives. They go up this whole ramp till their changing. And it can be kind of fun but obviously if I was going to make some kind of fire effect or kind of an emission effect, I wouldn't want the randomness to be that great, because I would want things when they came out of a rocket ship at the back to start out one color and kind of all kind progress to another colors they went to the end of it.
So that's a fast look of what you can do with Lifespan expressions and hopefully you can use this as a template. And you can start playing around on your own with it.
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