Embla

A simple rendering engine based on FRP.

Contents

• Definitions for signals using clojure.core.async, not yet fully functional
• Definitions for openGL callbacks instances generated on the fly and properly released
• A clojure version of the LWJGL example

Dependencies

General

Required:

• boot.clj - please install boot.clj and add it to your system PATH in order to be able to follow the usage directions below.

Obtained by boot.clj:

• LWJGL
• LWJGL native libraries -- beware, we download libraries for Linux, OSX and Windows for lack of a way to check what your OS is.
• PNGDecoder

Usage

Starting an Embla REPL

1. boot repl : launch a standard clojure REPL
2. (boot (build)) : build the project
3. (boot (run)) : start the Embla engine

Interacting with Embla

We provide macros that allow you to interact with Embla. These can be nested as much as desired, to build complex models in a single REPL submission.

You may also create a file regrouping macro calls and call (load-file <your_file>) within the REPL to achieve the same effect.

See the file src/clj/embla/examples.clj for a quick and dirty example of model and signal interaction. You can require the file to get a working example : (use 'clj.embla.examples) in your REPL will take care of everything for you.

Defining model objects

defgom

(defgom name) creates a GOM with root node ID name. Error if name is not a String.

defrect

(defrect {
  :x x
  :y y
  :length l
  :height h
  :id ID
  })

Creates a "Rectangle" node you can add to the GOM, with top left corner (x, y), height and length respectively h and l, and node identifier ID. All arguments are integers, except ID, which is a String.

(defcircle {
  :x x
  :y y
  :radius r
  :id ID
  })

Creates a "Circle" node you can add to the GOM, with center (x, y), radius r, and node identifier ID. All arguments are integers, except ID, which is a String.

(add-children target children)

Adds nodes in children (may be a list or a single element) to target.

Defining signals

We provide a timer signal emitting an integer representing time, as well as a keyboard-input signal emitting the string corresponding to the key pressed.

(defsig name channel)       ;; creates an embla signal.
(defsigf name code)         ;; registers a code snippet to the named signal
(combine name1 name2 code)  ;; combine signals name1 and name2, manage input
                            ;; signals with snippet code

The (broadcast-all) function is the main function to connect signals : after registering functions to signals with (defsigf), use (broadcast-all) to transmit informations from the signal to the function. (broadcast-all) is required for every new function registered to a signal.

Wishlist

• Sprites - not unavailable for lack of finding a way to display them in a way that reflects the rest of the shapes

License

Distributed under the MIT License.