Animated Flag

This is a tutorial on creating an animated flag using the built in tools of Maya without having to resort to the memory intensive Cloth simulator.

First off, ensure that in your Preferences – Timeline settings you have Playback Speed set to “Play every frame”. This is because the Dynamics Engine needs to know the values from the previous frame in order to calculate the necessary changes for your current frame. If you have it set to “Real-time” Maya will often skip frames to keep the playback speed at real time depending on your playback frame setting. Skipping frames like this will cause Maya to calculate improper Dynamic numbers and the simulation will fail. This is also the reason you cannot scrub your timeline when working with Dynamics unless you have created a particle disc cache.

Generate a NURBS plane and scale it to x = 17, z = 10. Set the U/V patches to 17 and 10, also. This will be needed when creating the springs later. You should make your spans as square as possible and you accomplish this by setting them to the same numbers as your scale factors. Rotate your flag to x = 90 so that you are working in a vertical position along the X-Y plane.

Ensure that your disc cache is turned off by using the pull down “Solvers > Edit Oversampling or Cache Settings” and uncheck the box marked “Use Particle Disc Cache”.

Create your softbody flag by using the pull down menu “Soft/Rigid Bodies > Create Soft Bodies > Option” and set the options to “Duplicate, Make Copy Soft” check “Hide Non-Soft” and “Make Non-Soft a Goal” with a Weight of 0.5 for now. This will hide your original NURBS plane and generate a new Soft Body surface using the original as a goal object for the particles being created.

Select the particles of the soft body and apply a gravity field. Set the Magnitude of the Gravity to 100 and play your animation. You should see your flag move down and then bounce back up. This is caused by the goals on your Soft Body trying to get back to their goal positions on the original NURBS plane.

What this means is that the particles on the edge of your flag that you want to stay strong and not be affected by fields need to have high goal weights (1) and the rest of the flag should have lower goal weights (0) so they move naturally with fields in your scene. For this you need to adjust the goalPP settings. To accomplish this you want to select your particles and in the Component Editor under Particles you want to select the goalPP and change their weights to 0. Then select the two columns of particles along the left edge of your flag and change their weights to 1.