Loopable flag

23Jan09

how to make a loopable cloth simulation using 3ds max

1. Simulation

Make a hi-res 2:1 plane, and add some geometry details for the seams.

Choose cloth settings for a whole flag (e.g. silk or satin).

Make two cloth groups – one for a cloth preservation near a flagstaff (with a small soft selection), and another for a heavier cloth at the seams imitation.

Change the seams group cloth settings to a more rigid (e.g. burlap or rubber).

Set up the gravity and a wind with the turbulence. Animate the wind’s direction and strength. For a better turbulence settings control I made a simple particle system and bind it to the wind space warp.

We are ready to run the simulation. You can also play around time scale to make the flag looking magnificent.

2. Point cache

When simulation is over – it’s time to make a point cache from it.

Apply the point cache modifier over the cloth.

Save the cache to the HDD and put the files to the network folder for a distributed render or backburner (For some reason exporting directly to the network folder doesn’t seem to be working).

Now get rid of the cloth modifier from the stack for a file size economy.

Make a copy of cached flag and choose a pair of the most epic simulation parts for a future loop using a playback type – playback graph.

To get a proper loop, the playback graph frame number of the first flag copy in the first frame needs to be equal to the playback graph frame number of the second flag copy in the last frame.

3. Morphing

As I noticed, simple morphing is not enough for a proper looping of the cloth anmation, so for the more natural cloth motion use the “wipe” morphing transition described below.

Apply the Vol.Select modifier to the first copy of the flag under the point cache. Animate modifier’s gizmo motion in the wind direction. It should come over to the flag with a huge selection softness.

Put the morpher modifier over the pointcache and choose the second flag’s copy as a morph target.

Turn on the automatically reload targets switch for an animated result.

4. Wrinkles

As seen on the reference videos there are small wrinkles appears around a seams which are looking good, however we still don’t get them so far.

Simulate the thin cloth stripe with fixed top vertices (selected every second vertex). Add some wind with small strength and huge turbulence.

Render the simulated stripe with self illuminated gradient material applied across and get the wrinkles displacement map.

Assemble looped construction from the rendered stripes and put it to the map slot in the displacement modifier over couple of turmosmooth iterations.

5. Texturing and render

Make the diffuse, bump and opacity textures from the cloth photos in Photoshop.

Make a vray2sided material with a vray material inside. Put the maps to the corresponded vray material slots.

Set up the lighting and render.

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