Use of Temperature over Density in Fluid Dynamics

Through experimenting with the settings of the guild dynamics systems I've found two ways to achieve the look i want.

The first method uses the density of the voxels in the fluid container, and applies a colour ramp based on the value. Meaning more the higher the density in the container, the brighter the colour. This relies on the opacity ramp being set to apply to the density, not the temperature and i think it looks passable.

I like the way it seems to spill out of the crevices in the torch model, but it is quite soft around the edges, especially in the less dense areas around the top of the flame.

The alternative method, more similar to what i experimented with using the candle flame, is using the temperature to determine colour. Whilst this looks very nice and has a slightly more realistic appearance it takes far longer to calculate, as the temperature is another layer of calculations added into the fluid simulation. I found that working with the temperature controlled container it would increase the render time very rapidly especially past the 30 frame mark. 

It seems that some of my settings are making it continue to simulate the fluid long past the point it is still visible, as with the container set to automatically grow it ends up 4 or 5 times larger than using the density method, meaning more calculations per frame.

I also experimented with making the flame collide with the torch, which whilst the physics behind it may be more realistic, it seemed to leave holes in the back of the fire when the torch was moved, and didn't add any meaningful benefits to my tests.

Surrealist Sculpt.

A piece that i have been working on for the last few days, i have started to realise that my necessity to conform with anatomy was holding me back, where as really all i needed were  few anchor points to put the idea that its a head into your mind.

Another popular theme in surrealist art are tentacles, or ling thin strands connecting parts creatures, in this image i used a large chunky tentacle going from where a tongue should be , into an eye socket, supporting the upper part of the head.

Another staple of Jase Daniels work is that his pieces look more like paintings than realistic renders. He accomplishes this through his strong composition, his stylised colour palette but also the use of layers textures, both on the sculpt itself and on the final image. 

This is something i have tried to achieve with this image, I've used the Spotlight feature of ZBrush to apply textures to the sculpt,  swell as making a conscious effort to admire depth to details across the sculpt, trying to make the shadows more intense.

In this piece i used the ear, and the shape of the eye socket as anchors to realty.

I feel like it is a successful image, but i lost some of the detail in the eye socket and across the skin. I also need to practice integrating my sculpts into the surroundings, using them to tell a story

the sculpt is partly inspired by this advert for foundation i saw while shopping, it made me stop and check whether her face was floating, and it was what gave me the idea to separate the face into blocks.

The sculpt finished in ZBrush, i used photoshop to add the colour and add some more textures to the skin. 

As i started needing more in-depth and detailed textures for my sculpt I've been experimenting with using photos to add detail. Ive found it gives me interesting and unique results far more quickly than trying to do it all by hand. Its also helped expand my texture library.

An intersting version of the image, i don't think its particularly useful but i do like the way that it shows the texture of the sculpt.

This was the final composition of all the render layers, textures and colours that i put into the image.

Jase Daniels and the Progression of my Project.

I recently stumbled upon the work of Jase Daniels, or Grot (his internet alias) and I'm completely enthralled. Ive learned a lot by studying his work and it has changed the way i think about my project and what i have been doing.

His work is the closest I've seen to Zdzisław Beksiński that is made in 3D and is a testament to surrealism in ZBrush.

A common theme that i have identified with surrealist design is that whilst some parts of the creatures are completely alien to what we know and recognise, but there are always anchor points in the anatomy that make our brains recognise it as human. With some of Jase Daniels work there is nothing that we would recognise as a face in the image, but because there is an ear, or a nose, or a hand nearby it forces our imaginations to recognise it as a head and this is something i would love to be able to replicate effectively.

I love the design of the creature in this picture, the recognisable arrangement of the limbs and the shape of the torso firmly cements the figure as being humanoid, but all of the fine details are so alien that it makes it a very interesting piece. The way the leg ends in what looks like a finger is very interesting, the wrinkles across the stomach give the model a texture that draws the eye, and the "head" with the gaping hole in it is very unsettling.

This piece is more human, but the movement of the left eye downwards and the craters in the face make it far less uniform and more interesting to look at. The lighting and dust particles give it the impression of being hidden in a dark room, and the composition with the right side being dark reinforces this impression.

This piece is slightly more human than the last, but the proportions are exaggerated across the neck and back of the head. 

This piece is completely devoid of a face, but is still clearly a head thanks to the ear, which anchors your imagination to seeing it in a  certain way.

Torch Model.

If i were to make the torch model myself, i know that i would probably spend far longer than i needed to making it, possibly at the detriment to the focus of the module, so instead i have acquired this model from Turbo Squid, by Makeionesco .

Available from http://www.turbosquid.com/3d-models/torch-max/633316

The torch is also split into two parts, meaning i can treat the cloth segment on the end as a separate object and use it as an emitter in Maya.

Progression of my project.

Recently I've noticed my work shifting further and further from he character design roots and more to making a final image. The influence of surrealist artists has definitely had a strong impact and I've started focussing more on the presentation of my work and less on the technical detail.

Ive been experimenting with sculpting using far more abstract forms, but trying to anchor the designs to reality using recognisable parts of anatomy. 

I would say the Vision Statement of my project has changed over the recent months and it has taken me a while to really nail down what i am doing but I'm confident with the direction that i have been going in, i just wish that i had the major break through in thinking a few months ago.

My new vision statement is 

The portrayal of surrealist imagery using ZBrush.

Flame with sparks.

Using a cube as both the emitter for the liquid container, and simultaneously as an emitter of nParticles that i was using to represent sparks.

The n particles are too small and un noticeable at the moment, especially in the final render.

The scene has three expressions running in it, one for the wind direction for the nucleus responsible for the n particles, one that changes the initial velocity of the liquid to simulate it being under the same wind effect as the nParticles, and one that changes the turbulence of the liquid to make it more natural looking.

Using the opacity graph i shaped the flame, using a slightly broader and longer flame than the candle.

Using the incandescance controls i linked it to the temperature of the flame, so the flame has realistic shading.

I wanted to make the flame have these small bits of flame left behind when it moves fast,  like in the top of the image but the effect is hard to reproduce and often looks bizarre.

Conjoined Sculpt

This idea, whilst not particularly original, has been floating around my head for a while.

Moving forward with more of the surrealist ideas that i had been working with, the manipulation of form, or rather lack of form, was something i wanted to examine.

Whilst trying to maintain anatomical accuracy i wanted to combine two bodies into one another, one almost tearing free from the other, but how would that work in 3D , could i maintain the sense of movement, but also the sense of ambiguity.

Starting with a sketch to establish the main blocks of anatomy i wanted to be in the final image.

I started out experimenting with the head, exploring the facial expressions and the way the skin would merge between the two.

Looking at ways other Zbrush artists worked, i decided to split the hands into separate tools, so i could easily manipulate the fingers and make the crease that appears between the hand and the shoulder more realistic.

The final composition.

I was greatly inspired by the sculpture "The Rape of Proserpina" the way the hands and the body pressed into one another, giving a real sense of weight and tension throughout the sculpture.

Whilst it would be vastly over reaching to say i aimed to get a look as refined and beautiful as this sculpture i feel like examining it helped me understand how i can bring some life into my sculpture.

Torch example

Starting Torch Simulations.

After using the fluid dynamics i wanted tot try something a bit different and perhaps more suited to games. Using nDynamics i made an emitter, and told it to decrease the size of the particles the longer they were alive. It certainly doesn't look as impressive as using the fluid dynamics but it is so much faster to simulate that i may look for a way to incorporate it into my project.

After that i made a simple torch model with two parts, and made a fluid container using the head of the torch as an emitter. Using the auto resize option for the container i animated the torch moving from the upper left to the lower right, similar to what i will have to do in the final piece.

I encountered a few problems with this method, using the fall off shape for the fluid container for instance. Because the fall off shape seems to be applied to the container as a whole rather than from the emitter, if the emitter moves to the edges of the container the flame starts to disappear at the bottom. 

As the flame moved it also left a trail behind, which isn't really what fire does, unless it is moving at a ridiculous speed and with a liquid fuel.

Next ill start working on adding sparks to the flame, and making the flame more realistically shaped as it moves.

Motion Fields in Liquid Containers.

Ive experimented with adding motion fields to props and moving them through the flames. Using the Vector Draw option in the Fluid Container you can see every force affecting a simulation.

Using Dynamics rather than nDynamics means that this is the only way to get my flame to interact with outside objects, so it was very helpful to learn.

However with the focus of the project being games, every extra calculation i add to the simulation makes it less and less suitable.

Liquid Dynamics for Flame.

To make the flame a realistic shape i used the opacity graph to only make certain areas of the flame visible.

This is the shape i was looking for, and to get the fade at the bottom of the flame i used a fall off shape. In this case i used a sphere. 

A final render i did of the candle flame. I was happy with how it turned out, and i think it will be very useful for my final project because it taught me the fundamentals of using the fluid dynamics and fluid containers in maya.

Play Blast and Render of Candle Flame.

Renders of the candle flame when i had finished setting it up.

Sadly after i output the playblast of the flame being influenced by a motion field maya died on me so i never got to finish rendering it. However , judging by the immense render time of the first clip, somewhere between one and two hours, i can safely assume maya will struggle with rendering fire for game engines.

Candle Flame, Dynamics.

Im working through a tutorial to create candle flames in Maya using the dynamics system.

So far I've learned how to create a fluid container and manipulate the fluid so it acts , kind of , like a candle flame. At the moment it looks more like smoke, but i will be changing it so soon it looks more flame like.

Dr. Michael J. Gourlay and Fluid Simulation for video games.

"Video games appeal to our desire to explore and interact with our environment, and adding real-world phenomena-such as fluid motion-allows game developers to create immersive and fun virtual worlds. Recently, physical simulations have become more realistic, but the simulations have largely been limited to rigid bodies. Pervasive simulations of continuous media like cloth and fluids remain uncommon, largely because fluid dynamics entail conceptual and computational challenges that make simulating fluids difficult. "  (Gourlay M, Fluid Simulation for Video Games (part 1), 2012)


These articles by Michael Gourlay show some of the incredibly complex systems behind simulating fluids for video games, though his system also explains how it can be used for fire in parts 9 - 13. 

Although using the mathematics and algorithms presented here is probably way above anything i could achieve this year, it can be used as reference to try to base my simulations in reality. 

https://software.intel.com/en-us/articles/fluid-simulation-for-video-games-part-9/

Simple Fire Tests using Dynamics.

Using the Dynamics menu and the create fire option I've done a few simple tutorials on the creation of fire in maya. Neither of these are very visually impressive and ill be looking into using the fluid system more in the future, but it was a good place to start.

By selecting the logs and using the create fire menu, when i run the simulation a flood of  green particles appear on the view port.

When i rendered it out the fire was unnaturally large for the campfire size, so using the attribute editor i changed the lifespan, starting size of the particles, fire scale, and intensity to try to make it more realistic.

This was the end result, a smaller, more manageable camp fire. This system however seems very simplistic and i think i can achieve much better results using the nDynamics fluid effects.

A problem with the simulation in maya is if you scrub through the timeline things can get a bit insane. The simulations run from one frame to the next and going backwards and forwards gets some strange results.

 The next part of the tutorial was adding that fire effect to the engine of a pod racer. After selecting one of the fins on the engine block and adding a fire effect from the dynamics menu, i messed around with settings to achieve the look i wanted. 

Initially the fire was far too long and not intense enough

After increasing the intensity and density of the fire, it was looking more striking but was still far too large.

 Then i reduced the lifespan drastically and slightly lowered the glow. Fires that are moving fast like this one would be are generally closer cropped to the source and in the previous renders it was too spread out.

Analysis of fire and how it would spread.

From a digital tutors tutorial "Creating Fire and Smoke using Maya Fluid Effects" there is a flow chart of the way fire will spread inside a house, and the order in which to consider your simulation.

This will help to maintain a sense of realism about any simulations i do, making me think about the source of the fire, the fuel its provided with, and how that can effect other parts of the scene.