[스크랩] Expressions to scale, rotate and spin by Aziz Khan, Afghanistan

Expressions to scale, rotate and spin by Aziz Khan, Afghanistan



Hello every one!! And welcome to Maya expression tutorial, in this tutorial I will show you how to rotate, scale,
and spin your objects thorough expressions using Maya, this tutorial is very handy to create, explosions like tank explosion, asteroid explosions so on and so forth. So let’s get started.

Step 1: Create any object you like to experiment with, in this I have created a piece of stone, as shown in the image below.



Step 2: Now go to your Dynamics module by holding down the (H) key from your keyboard and click. Select Create Emitter option box from the Particle drop down menu.



Step 3: Now change the following settings as shown in the image and Select Hit Create button.



like the following image. Then first select your object which you are going to instance then go to Particles drop down menu again then choose the option box for Instancer (Replacement).



The option box will appear for Instancer (Replacement) keep everything as default and then hit create, the picture is illustrating down.



Step 5: Now hit play button you can see the objects are emitting instead of particles and the size of objects are all the same and there is no rotation or spinning, so let’s start working on them.



Step 6: Go to the Window menu and bring up the Outliner to select the exact object, from the outliner window click on the Particle1 to select it on the viewport like the image below.



Step 7: Now open up your Attributes editor by (CTRL+A) from your keyboard, and then scroll down to button to find out (Add Dynamic Attributes) when you find it just hit the (General) button to create new custom attributes, so in the Attributes name choose any name you like it does not matter what you are naming it, but always keep the names close to what you are doing with it, since we are first dealing with (Scale) I will name it (Scale_new) so you can name it anything you like, if you are new to expressions I suggest you follow along with me to avoid any confusion.



Step 8: Ok now if you see in (Per Particle (Array) Attributes) you will see new name, the name will appear according

what name you have given in Attributes name, like the image below.



Step 9: Right click in the box of Scale_new then choose (Creation Expression) and write the following expression.

float $anything= rand(6,3);
particleShape1.Scale_new= <<$anything,$anything,$anything,>>;

if you want to play with the size of objects you can play around the numbers on the rand,





Step 10: Scroll up to find the (Instancer (Geometry Replacement) tab then on the (General Options) on the Scale drop down menu choose newly created name. In this case mine is (Scale_new).



Step 11: Now, if you play then you will see some random sizes of objects are coming out of emitter. It’s time to deal with rotation of objects so let’s create another (Custom Attribute) like we did before for Scale, again go to (Add Dynamic Attributes) tab and do the same as we did before, but the name should be different since we are dealing with Rotation, I name it Rotation_new so you can go regardless with any name you prefer.





Step 12: Now write the following expression.

particleShape1.Rotation_new= <>;



Step 13: Now go back to (Instancer (Geometry Replacement) tab on the (Rotation Options) choose (Rotation) then from drop down menu choose your custom name.

Now if you play then you will see on the objects they are not rotating instead they are oriented in different direction, that what we need next we will deal with spinning of objects.





Step 14: Ok last but not the least create one more custom name for our object spinning, name it as anything you prefer, but in this I have named Rand_rotation, now you have to change the vector radio button to Float radio button since we will deal with (Creation Expression) and (Runtime Expression).



Step 15: Write the below expression...

particleShape1.Rand_rotation= rand(-50, 40);

if you think these numbers too high you can decrease it to any satisfactory numbers.



Step 16: Anyway play your animation as you can see there is no changing on the spinning of the objects, ok we will add the expression for the spinning of the objects, ok open up your expression editor by default the radio button is set to (Creation) since we will deal with (Runtime Expression) ok hit the button called (runtime after dynamics) and then add this expression below...

particleShape1.Rotation_new += particleShape1.Rand_rotation;

With this you will be able to spin your objects.



I hope you find some thing new, so here is the small animation of my scene below.

* Related Links
Scene Setup: Download here
Authors Website: http://www.3dgroup.3dk.org
출처 : http://www.cgarena.com/freestuff/tutorials/maya/expressions/

Expression, 익스프레션