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nCloth Simulation in Maya

nCloth Simulation Report

Cart 434 Advance 3D Studio

By Umer Usman

Instructor: Stephan Menzies

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Index

1. Abstract

2. Introduction

3. Research

4. Tests a. Adding Backplate b. Matching camera focal length with the Backplate c. Setting up Ground plane and matching it with the Backplate d. Importing objects into the scene e. Adding Dynamics (nCloth and Fire) f. Adding Light Rig g. Final Result

5. Analysis

6. Conclusion

7. References/Inspiration

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1. Abstract

I wanted to do something in Dynamics using Maya Dynamics and from the start I wanted to do something using Maya proprietary nCloth system. There is a lot that can be done with nCloth not just Clothing on characters. So I wanted to explore the possibilities that could be achievable with nCloth and rendering those with my own ideas.

2. Introduction

The objective of this project is to learn the procedure implementing Maya’s nCloth system effectively. There is no technicality involved with nCloth per se but to understand the process and technical aspects of the materials that nCloth uses for example Silk, rubber, air bag etc. and how they behave according to the real world. Since the dynamics in Maya are built with real world properties, it is better to understand beforehand your project and study it and then apply those within nCloth system. Like I said in my abstract there is a lot that can be done with nCloth I chose to do the “Chinese Paper Lanterns” using nCloth. Using this I wanted to understand how nCloth works because nCloth and Dynamics go hand in hand and in doing so I’ll be learning two things at the same time.

3. Research

Before starting into Maya, I had to do research on the “Paper Lantern” how it behaves in the real world and what are it dynamics. There are two simple things that are involved with Paper Lanterns, it is made up of “light material” hence the word “paper lantern” and it uses Fire to propel/lifts itself in the air. I looked at the physics behind it and it is very simple. The idea is very similar to the large air Balloon. The hot air is lighter than the cold air hence the lantern starts flying in the air. The wax fuel cell then continues to fill the lantern with hot air which is why the lantern doesn’t fall.

a. Paper Lantern floating in the air.

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Tests

• Setting up Backplate First we create our SceneCam and looking through our SceneCam, we will add the back plate to it.

Looking through SceneCam

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Backplate looking through SceneCam

What is sensor size or crop factor?

In digital photography, the image sensor format is the shape and size of the image sensor. The series of pictures below will define for us what is sensor size or crop factor?

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• Finding the actual Focal Length The second most important thing to find is the focal length of the camera with which the picture was shot. This is extremely important because without this our geometry will not sync properly with the back plate. The focal length can be found using the Meta data that comes with the photo. All you need to do is to right click on the image > properties > detail tab. The image below tells us this information. In some photos the focal length is mention for a 35mm lens in Maya. In most cases it isn’t. For this we have to do a simple calculation which is, take the focal length of the camera with this the image is shot in our case it is 4mm. Next step would be to take the camera model Nexus 5 and do a quick google search to find out the crop factor or sensor size of the camera which is 7.61. We multiply 4*7.61 = 30.44 mm focal length for Maya.

Finding out the actually 35mm equivalent focal length of the camera for Maya

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• Setting up ground plane and match it with the Backplate Our goal here is to match the ground plane with Backplate so it syncs perfectly into our backplate. Once it is perfectly matched we will begin to import our objects into the scene.

Creating the ground plate for our backplate

Syncing ground plate with the backplate

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• Importing objects into our scene

Now will import our objects into our scene setup.

Imported objects in the scene setup

Rendered objects in the plate.

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• Adding Dynamic on to our objects

In this test I will apply dynamics such as nCloth and Fire. We will have to play with attributes to get the right settings. We have to turn off the “collide” and “self-collide” since there is no collision in our scene. I will be using the “Airbag” since our lanterns our paper lantern and this suits our need. For our lanterns to be properly be behaving according to the real world we will only need to adjust the, stretch resistance, bend resistance, compression, lift, mass and drag. After my ncloth setup, after this I will apply fire to my objects.

NCloth and Fire applied to the object

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nCloth applied properties

Airbag preset

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Adjusting resistance nCloth dynamic properties

Adjusting mass, lift, drag nCloth dynamic properties

Fire attached to the lantern with final settings

Attributes adjusted to get the final look

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More Fire spread with more Intensity

Fire spread to 1 and intensity set to 0.6

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Increased Flame start radius set to 2

nCloth and fire dynamics

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More testing with different fire settings

More testing with different fire settings

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Final look on the lanterns

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• Setting up light rig

Setting up light is a tedious work and requires great detailing which depends on how the lightning in behaving in the backplate.

Light setup using direction lights

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Light setting

Initial test using just cubes

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Shadows don’t seem to be quite realistic in this initial test and lightning is a bit off

Things needed to adjusted

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Test 2

Final result with correct lighting.

Area reflecting the brown light from the lamp post using direction light

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4. Final rendering

Once we are satisfied with our results we can go ahead and render out our scene and then we can do a batch render of our scene which will give images in sequence which are ready to be imported in after effects for our final composite.

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5. Analysis

At the end of the R&D and this project I achieved the desired results. Throughout this research I had to produce something of good quality and the problem is when I was doing this project many other thoughts kept coming to my mind and I wasn’t able to focus on anything and I was struggling to come up with something creative but none the less I have attained some relatively descent approach to nCloth techniques. I really wanted to use dynamics with nCloth to create cool VFX however I think it is nowhere near the professional level. According to my findings the only thing I struggled with was the attaching fire to the object. That was one of the major problems I found while preparing the object using nCloth. At first the nCloth worked and then the fire would follow the object. I tried using fluids and the parenting technique but it wasn’t following the object. While I was testing I found in the Maya’s online help about the dynamic create fire emitter that it can be attached with vertices. I tried that and it worked. From there on everything went smooth. Another problem I found was during the batch rendering mental ray was rendering the ground plane which it wasn’t supposed to. However, I couldn’t found a way to fix and everything in the render settings are default except the one’s need to be changed.

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6. Conclusion

I believe that at the end of this research I accomplished my goal of using nCloth in effective way. Though I feel I could’ve done much better with nCloth and come up with something better and using nCloth is not rocket science it is extremely easy to use but to use it a very creative way that is very hard for me. The problem was for to come up with something unique using nCloth and that was my struggling point. However, I achieved what I initially intended in the proposal without any major break downs which to create paper lanterns by using nCloth and dynamics to make it work.

7. Bibliography & References

http://www.youtube.com/watch?v=mTWC5pm29C0 http://www.youtube.com/watch?v=hwvJkHV-HW8

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