How to Play
3D Lawn - Help
Oxford Croquet is pleased to introduce a 3D lawn which allows you to view a virtual lawn in your browser in any orientation. Its intention is to permit high quality illustrations to be produced and also to load scripts to demonstrate manoeuvres and replay significant games.
Limitations in Running the Program
The calculation of the scene and its rendering requires a fast computer. Modern desktops and laptops should have no problems, but smartphones and tablets are going to be dismal. Even a 64GB iPad Air gives a very poor performance.
Your graphics card does not seem to support WebGL.
or the program remains on the loading screen. It is not worth clicking on the links! There are a couple of get-outs however. Firstly check the list of browsers below: You may find using a different browser on the same machine may work! You need the most up-to-date versions of these browsers to operate.
Using the 3D lawn
There are two 3D lawns, the simple and the coaching lawns. On the top right of the lawn is a link to this Help file. When you have finished using the either program shut down the tab in the browser to maximise your machine's performance.
Moving the scene
When the mouse pointer is over the lawn you can:
Things to try: zoom in on a ball to see the texture, look at the crown of a hoop, or rotate the lawn to look towards the setting sun to see the gleam from the grass.
When the mouse pointer is over a ball it changes to a hand , indicating you can now drag the ball when left-clicking the mouse. Whilst you are moving the ball its coordinates "x,y" are shown on the bottom status line. The lawn is dimensioned in inches.
When you drop the ball the last coordinates are held. These can be 'copy and pasted' by script designers.
There currently is no collison detection so one object can pass through another.
The On Screen Buttons
The features below are on the '3D coaching lawn' in addition to those above.
First there are the usual tape recorder buttons for controlling the scripts of ball movements:
Note the buttons above work when the balls have come to rest for the current step. There is no 'step back' back button.
Status and Control Bar
The white strip on the bottom of the screen is the status and control bar.
"Plummers" There is an information field showing the current speed of the lawn in Plummers. The control for changing the Plummers lies to its right. The lawns speed changes when all balls have come to rest. A low number results in a quick ball movement and vice versa. A 3-Plummer lawn would be like a meadow and a 19-Plummer lawn is approaching a sheet of glass. You can use this as a speed control for how quickly a script plays.
"Load:" allows selection of the available scripts. Selecting one will stop the current script and load the selected one.
"x,y =" shows a dragged ball's position whilst it is being dragged and locks when the ball is released. These coordinates can be copy & pasted.
"Script:" shows the filename of the currently loaded script.
About the Virtual Lawn
All web browsers should be upgraded to their most recent versions… this is cutting edge stuff.
Textures have been added to objects - see the surface of the balls or the crowns of the hoops.
The mottled green of the lawn makes it look better than plain green, which looks like a snooker table. I took an aerial view of lawn 3 at Surbiton and 'watered it' to make it a bit greener. I did try photographs of grass shoots but the scales do not work out. In this version the lawn is absolutely flat.
I have scaled up the dimensions of the hoops and balls. This is the reason that the balls 'merge' when they close together. Note currently there is no real collision detection, it is on the to-do list. At correct scale if you can see the lawn then the hoops and balls are a few pixels in the field of view. When you are standing by the side of the lawn psychologically the lawn furniture seems bigger - see video scale paper.
The motion of the balls follows the equation derived from lawn speed measurements which led to the naming of 'Plummers' for lawn speed; the balls experience a constant deceleration due to grass. There is a variable to set the Plummers for the lawn. (Cosmetically only, there is also one for the grass height!) The motion of the balls is purely sliding; no rotation is modelled. They are treated as hard spheres.
As a nicety the hoops extend beneath the lawn - look underneath. Thank heavens these are Plummer hoops not Atkins, since I do not know at the moment how to model four sided pyramids.
The program is asynchronous and event driven. E.g. you can swirl and zoom as the balls are moving. It does not rely on a simple loop to do the internal timing. Consequently if your computer goes away to do an intensive task before it updates the next frame in the animation, the frame it shows when it can get back is appropriate in real time. The ball may jump a little but it is where it would be if the animation had been uninterrupted. If the browser is minimised however the code stops running to allow your computer to use its computing power productively.
Why Do It?
It is also a useful coaching tool for showing manoeuvres. It can allow the viewer to step through a sequence of strokes to understand what is going on. It can replace clubs' magnetic boards for showing ball positions.
Additionally it can be used for showing important matches as in a movie/script but where you can keep selecting your view point.
The basic functions are:
The lawn coordinates are centred on the peg with the x-axis increasing to the East boundary (right) and the y-axis increasing towards the South boundary (down). The polarities of coordinates are shown in the diagram (right).
To make conversions straightforward I have used inches as the basic measurement, hence the location x=3, y=3 is 3" right and 3" down from the peg in the plan view. The Moving Balls section above shows you how to read coordinates from the screen. You can use decimals.
If you want to make your own model of croquet balls moving in a similar environment I have documented the equations I have used in the following two papers Modelling Ball Speeds, and Modelling Roquets.
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