Tips for 3D

Stories around the campfire …

Cut-sway view of 3D foot model
One form of 3-D Modeling …n

Visually describing how a track is created and changes through time is complex, some tips about how to accomplish it will ease that particular learning curve.

Accuracy is essential  …

To have value this form of illustration must provide accurate information, and the simulations must reveal, not just demonstrate.  The author requests anyone noticing an error to contact him as soon as possible.

Tailoring illustrations to how the mind learns …

The mind, seems it likes to figure things out for itself.  And then there are the old ways that evolved around man’s in-built love of a good story.  Campfire stories are not just fun shared moments.  The old stories and legends carry truths we all need.  A good story sinks into the mind like rain on parched earth, carrying the listener into a different experience, time, or soul, and the best teach as they sink in…

‘ “Not pointless,” I protested. “It’s the questions we can’t answer that teach us the most. They teach us how to think. If you give a man an answer, all he gains is a little fact. But give him a question and he’ll look for his own answers.” ‘ (quote from: A Wise Man’s Fear by Patrick Rothfuss)

Play – not only fun, it’s one of the most engaging and deepest reaching forms of learning and creativity.

Visual Zen koans …

Definition: “Zen koan” … a paradoxical anecdote or riddle, used in Zen Buddhism to demonstrate the inadequacy of logical reasoning and to provoke enlightenment. (definition from Google)

“Coyote Mentoring” …

“… a distinctive and highly effective educational approach developed by Jon Young and Wilderness Awareness School over the past 25 years …  This approach develops the capacities of students for learning, problem solving, and full expression, and re-awakens their natural sense of wonder.”
Source: https://www.wildernessawareness.org/adult/coyote-mentoring

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The Computer … An essential place to start!

Giant Massively Big Ancient Computer
An Ancient Version

Because of the complexity, this approach to illustrating the concepts can only be accomplished using a computer and appropriate software to simulate and reveal the processes without the foot obscuring essential internal details (except for when that helps the student learn).

A computer and the right sort of software make it possible …

Complex?  Just consider one part, what the computer and software are managing:

– calculating the locations and movements of the points (vertices) that make up thousands of objects, each with physics applied, and all potentially interacting … For each frame in the clip!

managing color, texture, sound, shade, light, and forces like gravity, wind.

 Not to mention running the user interface, etc.  Even with all possible corners cut, this is an astounding amount of work!

What is required?

The computer …

Fortunately, many off-the-shelf computers are able create simple 3-D scenes.  This is good because a maxed-out graphics-computer is not necessary at the beginning.  If your machine will handle Blender start with the computer you have.

Cooling is an issue you must always consider … Your computer’s processor and memory will generate significant heat doing this kind of graphics work, so monitor it carefully, and shut Blender down if you see signs of overheating.  There’s after-market cooling systems available, some work well, and there are even water-cooling systems out there!

At present, the apparent realism and the number of objects you can include in a scene are limited by the processing power of the computer used, the skill and knowledge of the creator, and to a small degree by Blender’s physics system.  Keep in mind that some computer configurations are significantly more graphics-capable than others, and with large numbers of objects (perhaps  more than ~10,000) a computer built for graphics work makes simulating physics go much better and allows for finer detail.

If you decide you want to move further with this work; an example might be creating enough realistically sized sand objects (with physics applied) to register an entire track, then you will need to have, or have access to an appropriate computer … the more graphics-capable the better … processor and type of graphics card does really matter … get LOTS of memory … and a bit more!

There are ‘physics cards’ available for some computers… worth checking out?

If you think you’ll continue doing this work, investigate, network, and search out what kind and configuration of computer you need … get the best you can afford, or build your own.

Backup and storage …

As you get into this work you’ll be creating lots of large files, some will be worth preserving.  You might want to keep only the most used or current Blender files on your PC’s hard drive and the rest somewhere else safe, like an external drive or on the Cloud.

Yes, you can get massive internal hard drives … And then your operating system has to keep that big drive organized, another demand on your system. Computers can be replaced, and, yes, data recovered from internal drives.  It’s far easier, and much cheaper to unplug that external drive and plug it into the new computer!  Really, why not … after all the work and problem solving that went into those files?

Places to start searching/networking for computer type and configuration (this is worth devoting some time to):

Blender.org / “About” / “Software” /click on “supported platforms” (it’s in one of the paragraphs) … Or just Google “blender 3D supported platforms”, or something like “Blender 3D best computer”.

Join BlenderArtists.org and ask..

There are companies that offer computers built with Blender and other graphics software in mind.  Some offer quality, some do a good job of standing behind their products, choose slowly.

Software …

The job is to use real-world physics with three-dimensional illustrations to simulate processes.  Blender 3D was chosen as the initial software because it is built to do that.

Blender is open source software and free … A capable and powerful 3D modeling platform … Well supported … Improved and updated regularly … And has a world-wide community of supportive users and thousands of free on-line learning tutorials.  Pretty amazing actually…

It is suggested that other 3D modeling applications be explored to decide whether one may be more useful for this work.  Not that there is anything wrong with Blender, it’s wonderful!  It’s just that, like most technology, software evolves and sometimes a different platform evolves to where it does certain things better.

Useful software features to look for:

What are the upper and lower limits of the number of physics-enabled objects the software can manage? Will it handle 500,000 Rigid Body objects? A million?

Can it simulate soil or clay?

Does it have “issues”?

A sand grain weighs a lot less than a foot … how well does the software’s physics engine do with large differences in weight or mass?

When a foot makes a step … what parts of that process need to be simulated?  Can the software simulate all of those?  As an example; when a foot pushes off from the ground the ball of the foot is pressing down and trying to rotate rearwards.  Friction of the foot surface, and of the sand act to keep the foot in place.  Any other thing that can move will, and that’s the body.

In that situation mentioned above, will the software allow the animation system (controlling the movement of the foot) to talk to the physics system (controlling the sand’s interactions with itself, ground, and the foot surface) so the force of the rotation of the foot is actually used to interact with the sand and propel the body forwards?  Will the animation system be effected by the resistance of the sand and make the foot surface deform accordingly

The primary simulation systems offered by Blender are: Cloth, Fluids, Particles, Rigid Body, Smoke, and Soft Body. There are also “Force Fields” which include wind and others.  They are very accurate with room for improvement.

Blender was originally intended to be a precise simulation system in terms of how real it appears, and each new update is nudging it towards greater accuracy, precision, and efficiency terms of how it performs.

Updates …

Blender is revised and updated at least once a year (author using ver 3.79).   Some users prefer certain versions for specific purposes.  When a new version of Blender becomes available, it is useful to visit the Blender website and read the “What’s New” info.  Occasionally it helps to use an older version, you can keep older versions installed.

“Detail” – It makes the computer work harder, so how much is needed?

Trackers tend to notice the slightest change in shading the eyes can detect, a line made by a single hair as it falls into soft dust, or a slight ridge, no taller than the cross-section of the hair that fell beside it.  An ant walked across newly exposed mud … See those disturbances left by it’s forelegs?

Use as much detail as required to carry a point across and provide validity, and avoid it where you can.

“Accuracy” – adds to the computer’s load.

Realistic appearance … is necessary, sometimes, and certainly wonderful.  Realistic appearance in these simulations may help, but isn’t always the only way to get a point across. Efficiency sometimes comes with accomplishing the goal the easiest way.

Accuracy in behavior … this matters

In Blender the behavior of objects can be controlled in at least two ways:

– Blender’s animation system can control the movement of any object, a foot for example.

– Blender’s Rigid Body physics system can control the behaviours of objects before, during, and after collisions, as in the creation of a track .

Rigid Body physics does simulate things accurately.  Accuracy of animation is largely up to the creator.

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Learning Blender 3D

Giant Massively Big Ancient Computer
Blender Controls…

Yup, same picture, it’s a fair representation of the complexity of the controls in Blender.  And that is only wall one of four!  But, no worries, you’ll usually need only a small subset.

Beginning steps you might explore:

Start w/ tutorials or massively simple project … Use a search engine to find them.  This will save hours and weeks!  (if you’re using Blender, and they used a relatively recent version most settings and methods should work just fine).  A well done set of beginner tutorials though a bit out-dated: Blender 3D Tutorials by Neal Hirsig

Blender has two rendering engines, “Blender Render” and “Cycles Render Engine”.  Learn with Cycles … Blender Render will eventually be obsolete.

Get help when you need it … especially while still learning the software.   Solving problems on your own is great, but with complex applications like graphics software you’ll likely frustrate yourself.

Play with it … What sounds interesting and fun to create?

Break problems down to bite-size chunks.

Persist.

As a bench mark: the author had many years work experience illustrating scientific papers for PhD theses and publication in journals, very little training in 3D graphics or simulation, and none in Blender.  From a cold start it took about a month to learn enough to produce simple video clips … And about 6 months to learn enough to create the first sign of a successful track…

Useful tip: When using Blender it sometimes happens that something you are working on doesn’t behave as you expect.  Usually this is NOT a bug and is operator error because Blender is so complex.  You most likely are not the first to hit this particular wall … A search with Google or within the Blender community can work wonders.

If you think you have found a genuine bug and have unsuccessfully searched for a solution, the Blender developers are quick to listen and resolve, so report it and include a copy of your “.blend” file reduced to the absolute minimum that reproduces the problem.

Help w/ Blender …

Google

Blender.org Website

BlenderArtists.org Website

BlenderStackExchange.com Website

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Plan Before You Illustrate … Timing (and once you’ve got that going, forget the plan and go with your gut)

question-mark-2

Timing, length of clips, and slow motion … these are worth planning!

In slow motion a foot stepping and the track forming, or degrading, are much easier to observe … And can have a certain elegance.

Roughly how many seconds do you want the scene to play?

Blender does animation using sequential frames (think picture) where a footstep is captured as one tiny bit of movement per frame.

24 frames per second (fps) is a minimum recommended frame rate, though you can choose your own.  At that rate a pleasantly paced slow-motion footstep takes something like 400 frames (400 images).   400 frames /24 fps = 16.7 seconds.  This includes a few seconds for comprehension before the track forms, and after the foot leaves.

How slow the motion is … that’s a matter of taste.  Once you’ve created your animation try a few different renders using various lengths of time to see which you like best.  One of the ways to do this is to play with changing the time used by going to the “Properties Editor” panel, look down to “Scene … Dimensions”,  then change the values in “Time Re-mapping”, and render again.

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Making Stuff Move …

 What is a step?

Relying, foot lands …
Trustworthy, earth embraces …
Details, left behind…

So you’re about to build a foot and will want it to take a step. How are you planning to make that happen?

Animation is a complex subject … So is a step.  Discussion of animation is limited to the use of Blender 3D for this project and intended only as a brief overview to offer insights to those unfamiliar with 3D modeling, animation, and Blender.

A step in Blender requires ‘key framing’ …

‘key’ – adjective: “of paramount or crucial importance” (Source : Google definitions)

‘frame’ – think of a drawing of that foot at one instant in time during a step

The key frames…

This is a good description:

“A frame is a snapshot of the scene at one moment in time. An animation consists of displaying a succession of frames representing successive moments in time; if these are shown sufficiently quickly (at least 24 frames per second), the eye is fooled into seeing smooth movement, instead of a succession of still poses.

Computer animation works in a similar way, except here Blender is your lower-paid assistant. You go to crucial points in the timeline of your animation, position and pose your objects/characters appropriately, and tell Blender that this is a key frame for the relevant transformations (positioning/rotation/scaling) of those objects/characters. Then when you run the animation, Blender will interpolate the specified transformation parameters between key frames, giving you smooth motion over those intervals.”
– Description is from: https://en.m.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Basic_Animation

There are at least three ways to make animated things move …

Animation

Key framing the movements of armatures (bones) with mesh objects (skin) attached.

Key framing the movements of mesh objects manually.

Physics combined with gravity

Blender uses a physics engine that provides collision detection, and simulates soft, and rigid body dynamics.

Forces – wind, magnetism, etc.

Problem 1: Making The Foot Move …

A Solution: Use an armature with a mesh foot object attached

To simulate a foot taking a step in Blender, one may begin by constructing and animating an armature (bones) that has a mesh foot object (the skin) parented to it.

“parented” … in 3-D graphics a seed, parented to its watermelon, stays in the same position within the watermelon, even as they roll down the hill, at least until the rock.

This arrangement allows Blender to control the surface of the attached mesh foot so that it moves with the armature (bones) in a way that is visually similar to how the skin moves when connected to muscles, tendons, and bones.

Armature With Mesh Foot Attached
Armature With Mesh Foot Attached

And here is a foot, animated by an armature and set as a Rigid Body object.  The foot was made to look like the mesh it really is just for this explanation.

Introduction To Blender Physics

Blender Rigid Body Physics

BulletPhysics.org

The Concepts of Tracking 


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Foot meets sand … Collisions

Discussion about collisions will be kept simple.  Essentially they are, sorta like this:   You make a choice … Your foot bangs against the world … The world responds … Other stuff happens.

Why this an essential concept …

Tracks are the results of collisions between foot surface and substrate (sand here).  So a simple version of simulating tracks on the computer is just simulating collisions.  Even though Blender does most of the work of managing collisions, a little understanding will save you time and help achieve better results.

What are collisions?

collision –  “3. Physics; the meeting of particles or of bodies in which each exerts a force upon the other, causing the exchange of energy or momentum.”   (Source: http://www.dictionary.com)

An example; one part of walking is maintaining forward momentum.  When we walk we’re expending energy to push against the ground, and this gives us forward momentum.  To accomplish this we make our foot intentionally collide with the earth in a controlled manner.  This begins the track, and initiates a series of collisions that happen between the skin, sand particles, and among the neighboring sand particles.

How does one simulate a collision on a computer? …

Collision Boundaries.  You assign a boundary to each object that you will want to collide.  Imagine two dots, each surrounded by a circle, or sphere.  As far as Blender is concerned the collision between the two dots happens when they move and their enclosing outer shapes touch. Boundary-based collisions are one way Blender and the computer decide when objects touch.

And here’s collision boundaries at work…

Which of those objects would you use to produce the most realistic sand behavior?  The dark green ones, with their tight collision boundaries maybe?  Because they will give the most precise collisions and look the most natural?

Why not leave out the extra complication of a boundary and just say the collision happens when the two objects themselves touch?

 Think about the letter “M” and a period “.” … How would you tell the computer when the “.” touches the “M”?  Which do you think might be easier to figure out collisions on?  How do you tell the computer where they are in a way that works for both different shapes?  Is their location at their center?  The upper left corner?

What if you enclosed each one in a sphere and told the computer they touch when the spheres touch?  It turns out that, for imprecise uses, it works well enough to say they touch when simple enclosing outer boundaries intersect (the Collision Boundary) and use their geometric centers as the location of the objects.

For precision in this work the sand objects need collision boundaries shaped pretty much exactly like each sand object (look closely at the green sand objects), the foot needs one that is nearly identical to any part of its surface contacting the sand objects, and the ground needs one matching its upper surface.

In Blender the Rigid Body system the “Convex Hull” or “Mesh” collision boundaries  offer the most precise control of collisions.

What goes on when a collision is happening?

Nature is always applying the rules of physics to everything.  To the colliding objects as the collision occurs, and to every collision that follows.  We’re doing the same thing on the computer.

A simpler version?  Gravity is always on, and when one object collides with another energy is transferred, colliding billiard balls are a good example

Is it really that simple? 

For dry-ish sand, ‘Yes’ with complications.  In other cases, ‘No’.  An example of ‘no’ are the more complex collisions of wet sand … What holds a sand castle together?

Cohesiveness:

“2. Cohering or tending to cohere; well-integrated; unified: a cohesive organization.

3. Physics. of or relating to the molecular force within a body or substance acting to unite its parts.” (Source: http://www.dictionary.com)

When simulating a foot making a track, there are three essential components, the foot, the substrate, the ground beneath the substrate, and physics (Sorry, that’s four … too much Monty Python?).

Topsoil is one of the most common substrates and comes in many compositions.  Sand was chosen as the first substrate to use for this project because it’s a good place to read tracks, can be simulated more easily than something like clay soil, and the Rigid Body simulation does a good job … with one exception, cohesiveness.

Clear examples of cohesiveness are observed in damp sand (grab a handful, squeeze and then open your hand), the disc formed by the toe of a shoe, and a plate formed at the edge of the track wall by pressure against the wall, or by the ball of the foot.

Cohesiveness of sand is primarily the result of the surface tension of the water coating the surfaces of two or more sand grains and connecting them. Some aspects of sand behavior can be simulated to a degree by adjusting the friction and damping settings applied in Blender to the sand objects, but not cohesiveness.

To simulate cohesiveness the simulation system must address this connectivity between soil and/or sand particles in some way.  The author explored Blender’s other simulation systems to accomplish this and then tried a Blender add-on for Blender’s Particle System.  That add-on, the Molecular Script (by Jean-Francois Gallant), directly addresses the cohesiveness issue, is very well done and was recently updated.  It requires a more talented computer than the author currently has access to.

One other way to address this problem … different software.  Houdini by SideFX was explored by contacting the developers and explaining the problem. They indicated Houdini will handle this issue. Unfortunately, after installation, the computer presently used took a bite of Houdini, and said, “That ain’t gonna happen …!”  Ended that discussion.

This cohesiveness problem is mostly about computer processing power, and solving programming issues.  It has been addressed and resolved, so it’s just a matter of finding the right software. Furthermore, given the rate of change in computer software and hardware,  it is likely that other solutions already exist and just need to be discovered, so this issue is no permanent barrier.

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Testing the Illustration Substrate … Sand (as an example)

The idea: Test various Blender Rigid Body settings and simulation systems with sand objects to find the settings that hold a track the way you are trying to simulate.

This particular example is aimed at creating some aspects of damp sand behavior. One indicator of success will be when the ‘sand’ holds the track wall after the ‘foot’ leaves.

Sand is like the weather: its behavior is constantly changing and moisture content has a lot to do with that. In the morning a clump of squeezed wet sand holds its shape while resting on your palm, and if you had the patience and stamina to hold that position till it dried out, the dry sand would eventually trickle through your fingers.

The clip above was set up so the camera angle included the track wall of 5 various sand samples, each with a different physics setting.

One thing to notice: in the first part of the clip as the sand objects flow outwards before the ‘foot’ has stepped, the bottom-most group of sand objects is behaving much like dry sand.

After the ‘feet’ have lifted away, the top group of sand objects is reacting much like wet sand, in that it is holding the track wall.

The behavior of substrate objects is critical for these simulations to work accurately, be believable, or convey the correct information.  Moisture content, surface tension and cohesiveness are important contributors to substrate behavior… and track formation

Watch your own work … Does it convince you?

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