Date Assigned Jan 23 2001

Due Date:  Jan 30 2001

Reading: Using Maya Dynamics, Part 4 (particle collisions), Part5 (goals), part 6 (soft bodies), part 7 (springs), part 8 (rigid bodies), part 9 (rigid body constraints)  in  D:\AW\Maya3.0\docs\en_US\html\UserGuide\Dynamics\Dynamics.htm

Now press F8 to return to object mode. 

Next, switch back to your front view. Select the flag surface and in your dynamics menu click on Bodies>Create Soft Body-Options.

In the option box set the following:

• Creation Options to Duplicate, Make Copy Soft
• Hide Non-Soft Object to On
• Make Non-Soft a Goal to On.
• Goal weight to 1.0.

Setting the creation options Make Copy Soft to On makes a copy of the object a soft body without altering the original object. Switching Hide Non-Soft Object to On will hide the non-soft copy of the object so that only the soft body is shown. Turning Make Non-Soft a Goal to On to on will make the soft body trail or move toward the goal object made from the original or duplicate geometry. You are able to control how closely the soft body follows the original by adjusting the goal weights on the C.V.s. A goal weight of 1.0 follows the original exactly, a goal weight of 0.0 will not follow the original and will be completely influenced by dynamic forces.

Create explanation of gravity, turbulence, air, & drag

Use the Outliner window to select the air field. Move the air field to the middle of the flag in the front view, and slightly behind the flag in the top view. 

Select and move the turbulence field into the the very center of the flag. 

The next step is to tell Maya to have the fields influence the soft body. Select the Windows->Relationship Editor->Dynamic Relationships. menu option. Scroll down to select copyOfFlag, highlight the fields in the right hand window.  Now, close the window. The fields will now influence the flag.

Set the Max Distance to 1.0, and set the Wire Walk Length to 3. Click on Create. 

The Wire Walk Length determines how many springs are created between edge particles. For instance, for each edge particle, the value 3 creates springs to all edge particles within a distance of three particles.  These springs will give the flag internal structure and will improve upon the deformation control. The Max Distance attribute tells Maya not to create springs if the distance between the two particles that may be potentially connected by a spring is greater than the number specified in the field.

Playback your scene. While these forces are connected and acting on the soft body, you are not getting any results. This is because of the fact that when you created the soft body, you assigned a goal weight of 1, which results in the soft body always achieving its goal of maintaining it's original shape. You will need to adjust the goal weights of the individual particles so that the soft body will not always achieve its goal. For this you will use the component editor to assign goal weights to the vertices of the flag.  

Hold down the Shift key, and select all of the particles in the first 2 columns, except for the first two vertices in the upper left hand corner, and the first two vertices in the bottom left hand corner (see figure).  Select Soft/RigidBodies -> Paint SoftBody Weight Tool options box.  Choose 0.3 for Radius (U) and (L), this determines the radius size of your paint brush.  Since our flag CV's are relatively close to each other, we want to choose a smaller/finer brush.  Under Paint Operation, select Replace.  Enter Value - 0.2, Min/Max Value 0 and 1.  Select Close.  Now you should be able to paint on the flag.  Do so for the entire flag.

First select the turbulence field, and then select Windows->Attribute Editor. In the attribute editor, set the magnitude to be 30, the attenuation to 0, and the frequency to 3600.  

Now select the air (wind) field. In the attribute editor, set the magnitude to 30, the attenuation to 0, and the direction to 1.0, 0.0, 1.0.

Finally, select the gravity field. In the attribute editor, set the magnitude to 1.

The turbulence field causes random distortions over the surface of the flag. The air field simulates a wind coming from behind the flag and to the left. Finally, the gravity field causes the free end of the flag to realistically dip down relative to the end at the flagpole. The attenuation of zero means the forces will apply equally throughout all space instead of dying off.

Play back the animation. 

Adjust the frequency of the TurbulenceField to reach desirable flapping effect.

Next, you will need to scale and move the plane to the proper location. With the plane selected, enter the following values in the channel box:

• Translate X: -17
• Translate Y: 56
• Translate Z: -2.7
• Rotate X: 0
• Rotate Y: 0
• Rotate Z: -140
• Scale X: 56
• Scale Y: 23
• Scale Z: 13

You will now noticed that the plane has been scaled and positioned above the flag.

• Under Emission Attributes change Rate to 0.8.
• Under Emission Speed Attributes change Speed to 20.

Set both the Radii of the Tube attribute, Radius 0 and Radius 1, to be 0.05.

You will now create an expression for the Tail Size of the particles. In the box next to Tail Size, right click and select the Expression Editor. Set the tail size of the rain to be a random function between 0.3 and 1, using the rand function. In the expression editor, enter the following line:

particleShape1.tailSize = rand(0.3, 1);

In the Add Dynamic Attributes section, Click the LifeSpan button, and select the checkbox to add a Per Particle Attribute. This will determine the amount of time the particles will travel before they die out. Again we will create an expression for the lifespan.

In the Per Particle (Array) Attributes, right click in the lifespanPP box, and select the expression editor. In the expression editor, enter the following line

particleShape1. lifespanPP = rand(3,4);

This will assign the lifespan of the particle to be a random value between 3 and 4.

Now playback the animation. You should see rain particles being emitted from the plane toward the ground.

First open the Multilister Window by selecting Windows>Rendering Editors>Multilister. 

In the MultiLister, create a new Particle Shading Group (Edit > Create > Volumetric Materials; the new group will be listed in the materials section of the MultiLister) and name the ShadingGroup particleRainSG.

Open the Attribute Editor for particleRainSG by double-clicking on the shader icon in the MultiLister Window.

Set the Color Attribute of the shading group with RGB values of 0.73, 0.895, and 1.0.  

Next map the Transparency attribute of the shading group with a ramp texture. 

Set the ramp texture with the following values:

Finally, set the Noise to 1.0 and the Noise Frequency to 0.15.

Now that the shader is complete, assign it to the Rain Particles. 

When you playback the animation at this point you will see that the flag is now fluttering in the wind. Go to a frame where the forces have evened out and in the menu go to Solvers > Initial State > Set for all dynamic. You now avoid the first couple frames where the forces need to start up.