Godot: Dragging and dropping physics objects video

Series: 2D Shapes, drag and drop, new objects

Continuing to explore the Godot 3 game engine. I want to make a game where you drag blocks around and balance them on each other, but I couldn’t find much documentation on how to drag-and-drop objects (except menu UI elements), and especially I found quite a few wrinkles when doing this with objects that are normally controlled by the physics engine.

This time we actually write some code in Godot’s programming language, GDScript.

Godot version: v3.0.6.stable.official.8314054

Graft Animation Language on Raspberry Pi

Because the Rapsberry Pi uses a slightly older Python version, there is a special version of Graft for it.

Here’s how to get it:

  • Open a terminal window by clicking the black icon with a “>” symbol on it at the top near the left.
  • First we need to install a couple of things Graft needs, so type this, then press Enter:
    sudo apt install python3-attr at-spi2-core
  • If you want to be able to make animated GIFs, install one more thing:
    sudo apt install imagemagick
  • To download Graft and switch to the Raspberry Pi version, type in these commands, pressing Enter after each line.
    git clone https://github.com/andybalaam/graft.git
    cd graft
    git checkout raspberry-pi
  • Now, you should be able to run Graft just like on another computer, for example, like this:
    ./graft 'd+=10 S()'
  • If you’re looking for a fun way to start, why not try the worksheet “Tell a story by making animations with code”?

    For more info, see Graft Raspberry Pi Setup.

Worksheet: “Tell a story by making animations with code”

I’m running a workshop at the Egham Raspberry Jam on 21st October. The workshop will introduce my little animation language Graft. We will tell a story using animations that we created ourselves using code.

The worksheet for the workshop is here: PDF or ODP.

I reproduced it as images below.

Any feedback much appreciated.

My experience upgrading to Elm 0.19

Elm is unstable, so upgrading to the next version can be painful. Here’s what I needed to do to upgrade from 0.18 to 0.19.

  • Replace elm-package.json and tests/elm-package.json with elm.json – e06f5a1728
  • Switch to the new elm-testb964b7c7a
  • Re-arrange Main, and how we call it from JavaScript – 0c118c49f
  • Stop using eeue56/elm-all-dict (since it’s not ported to 0.19 and porting it looked hard due to a lack of Debug.crash) – fe100f256
  • Replace toString with String.fromX or Debug.toString – 9e78163d0a3
  • Stop “shadowing” names by making new variables with the same name as another in the scope – 9688a621de
  • Adapt to the changed Html.style function – b991ab4f
  • Stop using Debug.crash – f98a70ad1
  • Adapt to the changes in the Regex module – 856762a4
  • Stop using tuples with more than 3 parts – 472c0bb7

The lack of Debug.crash is really, really painful, especially for a library like eeue56/elm-all-dict that has lots of invariants that are hard or impossible to enforce via the type system. On the other hand, if Elm can give a hard guarantee that there will be no runtime errors, this seems pretty cool. The problem is that some code may well have to return the wrong answer silently, instead of crashing, which could be much worse than crashing in some use-cases.

I was annoyed by the lack of more-than-3-part tuples, but even as I did the work to change my code, I saw it get better, so it’s hard to argue with.

The hardest part to work out was how to run the tests. Fortunately the tests themselves needed almost no changes. I just needed to do this:

rm -r tests/elm-stuff
rm tests/elm-package.json
sudo npm install -g elm-test@0.19.0-beta8
elm-test install
elm-test

My next job is to check out the –optimize compiler flag, and the advice on making the code smaller and faster.