Three JS and Physics Behavior Testing

Lab1 experiments with shadow effects and keyboard control. The small cube is the "test subject". There is a small octahedron on the forward facing face so that you can keep track of your orientation. This lab is not "mobile device friendly" except for when using Orbital Controls because I have not incorportated any kind of pointer select with grab/drag features (future lab). The following keys control the small cube's behavior:

This lab begins to setup our solar system to scale. For now I have placed both the sun and the earth into the scene, together with a ship.

• Added dat.UI, which is a simple UI component. I've added movement and view controls, which will be handy for non-keyboard use case.
• Added a reticle for the forward view.
• Added highlighting for when acceleration or rotation in a particular direction is active.
• All units are metric. Distance is measured in km.
• The acceleration slider configures how much acceleration will be applied when one of the movement controls is activated. Acceleration ranges from .1 G to 80 G.
• Added Targets. Currently there are two targets: Earth, Sun. Selecting a target rotates the forward view in that direction; subsequent acceleration in forward direction will accelerate toward target.
• Fixed bug when using target option.
• Increased Acceleration maxiumum from 8 to 80.
• A big source of confusion for me was the difference in the coordinate system convention used by Blender and Three. Both are right handed, but in Blender, the "y" axis points into the screen, the z axis is vertical, and the x axis is horizontal; whereas in Three, the x axis is horizontal, the y axis is vertical, and the z axis points out of the screen. Also, in Three, the "get world direction" method returns the direction coordinates for the local z component of an object. I used Thing children cameras to fix orientation of the object that I created in Blender, but originally I did not compensate for the differences in the coordinate systems (this is what caused problems with the target option). If defining "forward" for a Blender object by using a camera, it's important for the forward direction of the object to be aligned with the "y" axis, in the negative direction, so that when it is ported into Three, the forward direction will be pointing in the positive "z" direction (which is what Three will use when computing the global direction vector for an object). Alternatively, I could rotate the object after importing it into Three so that I don't need to worry about orientation within Blender.

Fun factoid: humans can only handle approximately 2 G for any sustained period of time. Anything over 2 G starts to get very uncomfortable. Something like 80 G -- which is what the acceleration slider will allow you to use for the shp -- would kill a human. So, if you want a "realistic" experience, keep acceleration below 2 G. It will give you an appreciation for the distances and object sizes in this simulation. Also, when you can only accelerate at 2 G, or maybe 3 G, mistakes in your navigation will become apparent when you try to postion the ship into an orbit :) 80 G is for wusses unless you are travelling to the sun (which would be masochistic at anything slower than 80 G :))!

As a reminder, for now there is no managed session state, so a page refresh or any navigation from simulation page, will reset everything.

• Added "Align To Target" option to align to currently selected target.
• Added gravity. Both the sun and earth gravity are accounted for in the motion mechanics.
• Added a crude collision mechanic: if the ship collides with either the Earth or Sun, its position and velocity are set back to initial conditions (i.e. earth view). It is possible to "cheat" collision at extremely high velocities :p
• Added "Target Distance" to Target Control. This is distance from ship to center of target. TODO change so that distance is measured from ship to SURFACE of target.
• Added "Radial Speed" to Target Control.
• Added "TVOR - Speed" to Target Control. TVOR is my acronym for Transverse Velocity Orbital Requirements. The TVOR values help to manually enter a stable orbit. TVOR Speed is the transverse Speed needed for a stable circular orbit at the current target radius. Because of interpolation errors, it turns out the actual simulation speed at LEO (Low Earth Orbit) is about 0.7 km/s less than TVOR Speed, something to keep in mind if you are trying to get into a stable orbit. In one of my test runs, I got into a fairly stable orbit at 9,666 km (atual distance from earth center), with a Forward Speed of 6.42 km/s (TVOR Speed indicated 7.1 km/s, but that is a little too fast because of simulation errors). At that speed, I had a slow positive radial speed (tending toward negative) of 0.0098 km/s.
• Added "TVOR - Alignment" to Target Control. TVOR Alignment is 1.0 when the Up direction vector is exactly parallel to the radial direction vector. This is the most important value to look at when managing orbital entry. The procedure I used goes like this when starting a new session: (1) Pitch up until the earth is centered in the "down" (key 6) view. Get TVOR Alignement as close to "1" as you can. The closer to "1" the more aligned your up direction vector is with the vector directed from earth to your ship. To make small pitch/yaw/roll adjustments, use the key commands (z, x, q, e, r, f). (2) Max out the acceleration to 80. (3) Accelerate down, "Move Down", until you get within a few thousand km of LEO. LEO is any oribt 2000 km or less, which means a radial distance of 8400 km or less. I fudged a little and aimed for an orbit of 9600 km. Make sure to "Move Up" well before you reach your desired altitude :) (4) Every time you want to apply thrust in any direction, first get TVOR Alignment as close to 1 as you can (this will likely mean periodically doing a "pitch up/down"). (5) Move Forward until the forward speed matches TVOR Speed. What you want is Forward Speed = Speed = TVOR Speed, with Radial Speed as close to zero as you can get. In reality though, Forward Speed will need to be less than TVOR Speed to reach a stable orbit (one where the radial speed is changing very slowly). (6) Periodically dampen any small velocity in the "Left" direction axis (i.e. keep value as near to zero as possible). (7) If all goes well and yo are in a stable orbit, all you need to do is periodically pitch down to bring TVOR Alignment near to 1 and then perform small adjustments to forward speed if necessary. When I have placed the ship in LEO, once I got the initaial orbit stable, I did not have to make any adjustements (other than pitching down for the correct orientation). My radial distance fluctuated between 9666 km and 9832 km, which I think is pretty damn good! On the second orbit, minimun distance was 9535 km, so the oribit is not perfectly circular, which is not a surprise. Not sure how stable the orbit is either.
• Added "TVOR - Yaw" to Target Control. "Yaw" is a litle misleading, but I use it because if the up vector is aligned with the target radial vector, yaw changes are what most likely will cause your forward direction to be pointing differently than the forward veloctity vector (TVOR Yaw is simply the DOT product of your ship forward direction vector with the ship velocity direction vector, and since you are keeping Up normal to your desired velocity, it will be yaw motion or Left acceleration that make TVOR Yaw vary from 1.0). If you have applied any Move Left in this procedure, chances are you will need to correct your yaw or roll if TVOR Yaw is not close to 1. In general though, you should not need to make adjustments for yaw/roll if you kept your ship Up direction vector perfectly aligned with the earth radial vector (i.e. you kept TVOR Alignement as close to 1 as possible when applying any movment controls). Don't use TVOR Yaw to make any corrections until after stabalizing TVOR Alignment (usually by making adjustments to pitch); you will find that when TVOR Alignment is near 1, so is TVOR Yaw, unless you have velocity that is not transverse to rotational plane.
• Added Info section. Moved global position vector and velocity vector of ship to here. Use "show" to refresh values. TODO Add gravitational acceleration values (earth and sun).
• TODO Add moon.
• TODO Define your standard for object orientation and use it to apply rotations when using gltf.
• TODO Add a camera to view ship.

This lab is also the index reference.

A place to sample snippets of javascript to test compatibility. Also a place to view icons.

Test galaxy generation.