# Anaglym Documentation

Anaglym exposes a Lua library named `ag` which contains functions for interfacing with the Engine. In addition to the `ag` library, there is a `std` library which contains a "standard library" of Lua functions that do not directly interface with the Anaglym engine. The library functions are documented below.

- `ag` library
  - object creation functions
  - object member methods
- `std` library
- Lua Event Handlers
- Key Names

## `ag` library

### clearEventHandler

`ag.clearEventHandler(event_name)`

This function removes a Lua callback function from being associated with the engine event specified. `event_name` should be a string containing an event name. See Lua event handlers for a list of events.

### doPhysics

`ag.doPhysics()`

This function invokes the physics processing part of the engine. It is invoked automatically every update step if the "AutoPhysics" mode is enabled; this mode is enabled by default. See setAutoPhysics for more information.

### drawArc

`ag.drawArc(r, g, b, x, y, radius, a1, a2)`

This function tells the engine to draw an arc to the screen. The color of the arc is specified by (r, g, b). `x` and `y` specify the coordinates of the center of the arc. The arc ranges from angle `a1` to `a2`, which are specified in degrees, going counter-clockwise from the East. `drawArc()` should normally be called from the `update_overlay` event handler.

### drawCircle

`ag.drawCircle(r, g, b, x, y, radius)`

This function tells the engine to draw a circle to the screen. The color of the circle is specified by (r, g, b). `x` and `y` specify the coordinates of the center of the circle. `drawCircle()` should normally be called from the `update_overlay` event handler.

### drawImage

`ag.drawImage(width, height, x, y, texture, [, rot])`

This function tells the engine to draw an image to the screen. `width` and `height` specify the size of the image, in pixels. `x` and `y` specify the coordinates of the center of the image. The image to be drawn is specified by `texture`, which should be loaded by `ag.loadTexture()`. `drawImage()` should normally be called from the `update_overlay` event handler.

### drawLine

`ag.drawLine(r, g, b, x1, y1, x2, y2 [, width])`

This function tells the engine to draw a line to the screen. The color of the line is given by (r, g, b). The start and end coordinates of the line are (x1, y1) and (x2, y2). `width` is an optional parameter and defaults to 1 if not specified. It controls the width of the line to be drawn. `drawLine()` should normally be called from the `update_overlay` event handler.

### drawObjects

`ag.drawObjects()`

This function instructs the engine to draw all visible objects. It is invoked automatically every update step if the "AutoDrawObjects" mode is enabled; this mode is enabled by default. See setAutoDrawObjects for more information.

### drawRect

`ag.drawRect(r, g, b, width, height, x, y [, rot])`

This function draws a rectangle to the screen. The color of the rectangle is given by (r, g, b). The size is given by `width` and `height`. The center of the rectangle is given by (x, y). `rot` is an optional parameter that defaults to 0.0. It specifies the rotation of the rectangle. `drawRect()` should normally be called from the `update_overlay` event handler.

### drawText

`ag.drawText(message, r, g, b, ptsize, x, y)`

This function draws the text `message`, which should be a string, to the screen at position (x, y), with color specified by (r, g, b), and with font size `ptsize`. It should normally be called from the `update_overlay` event handler.

### elapsedTime

`elapsed_msec = ag.elapsedTime()`

This function returns the number of milliseconds that have elapsed since the beginning of the program.

### endFrame

`ag.endFrame()`

This function signals the engine that all drawing is complete for the current update frame. It is invoked automatically if the "AutoEndFrame" mode is enabled; this mode is enabled by default. See setAutoEndFrame for more information.

### exit

`ag.exit()`

This function instructs the engine to exit. Internally, this function enqueues an "exit" event on the event queue to be processed by the engine. This means that Lua code following the call to `exit()` will be executed and callbacks to other events may still be called. The engine should exit within one update step.

### fillRect

`ag.fillRect(r, g, b, width, height, x, y [, rot])`

This function draws a solid, filled rectangle to the screen. The color of the rectangle is given by (r, g, b). The size is given by `width` and `height`. The center of the rectangle is given by (x, y). `rot` is an optional parameter that defaults to 0.0. It specifies the rotation of the rectangle. `fillRect()` should normally be called from the `update_overlay` event handler.

### getCamera

`eye_x, eye_y, eye_z, center_x, center_y, center_z, up_x, up_y, up_z = ag.getCamera()`

This function returns the camera position (eye coordinates), focus position (center coordinates), and up vector for the current camera settings.

### getTextSize

`width, height = ag.getTextSize(message, ptsize)`

This function returns the width and height, in pixels, that the text specified by `message`, which should be a string, would take when drawn to the screen using font size `ptsize`.

### getScreenSize

`width, height = ag.getScreenSize()`

This function returns the dimensions of the engine window, in pixels.

### import

`ag.import(lua_source_name)`

This function instructs the engine to import a Lua source file named `lua_source_name`, which should be a string specifying the name of the Lua library without the ".lua" extension. Source files are searched for relative to the folder containing the hosted script first, then relative to the engine library folder. The `import()` function can be used to load Lua code that is broken into separate source files, and to load libraries such as std.

### isKeyDown

`result = ag.isKeyDown(key)`

This function returns a boolean value for whether or not the key given by `key` is currently pressed or not. `key` should be a string corresponding to a key name. See Key Names for key names.

### loadModel

`object = ag.loadModel(model_name [, scale])`

This function loads an object file and returns the object loaded. If the returned value is `nil`, loading of the object failed. `model_name` should be a string specifying the base name of the model file, without the ".obj" extension. Models are searched for relative to the folder containing the hosted script first, then relative to the engine library folder. `scale` is an optional parameter that defaults to 1.0.

### loadModelStatic

`object = ag.loadModelStatic(model_name [, scale])`

`loadModelStatic()` is the same as `loadModel()`, with the exception that the object loaded is created as a static object. A static object can still be placed with setPosition() and setRotation(). A static object will participate in collision detection when physics computations are performed, however a static object will not be moved by any colliding objects.

### loadTexture

`texture = ag.loadTexture(texture_name)`

This function loads a texture file from the file system and returns a Lua reference to the loaded texture. `nil` is returned if loading the texture fails. The `texture_name` should contain the file extension, since multiple formats are supported (.jpg, .png, .bmp, etc...). Textures are searched for relative to the folder containing the hosted script first, then relative to the engine library folder.

### print

`ag.print(args...)`

This function prints its arguments to the standard output. It is mainly used for debugging when developing Lua scripts. On Windows, this output stream may be redirected to a file (stdout.txt). Example usage:

    local x, y, z = my_obj:getPosition()
    ag.print("my_obj position: (", x, ", ", y, ", ", z, ")")

### println

`ag.println(args...)`

Identical to `print()` but automatically prints a newline ("\n") after printing the arguments.

### registerEventHandler

`ag.registerEventHandler(event_name, handler)`

This function registers a Lua callback function (`handler`) to be called when the engine event specified by `event_name` occurs. There can be only one registered handler per event, so if a previous Lua function was registered for `event_name`, it will be overwritten to call the new handler. `event_name` should be a string containing the name of the event. See Lua event handlers for a list of event names.

When the Lua script is initially loaded, any functions found that have names matching an event name with "_event" appended (ex. "mouse_motion_event" for the "mouse_motion" event) are registered automatically as handlers for their corresponding events.

### setAutoDrawObjects

`ag.setAutoDrawObjects(enable_flag)`

This function sets the "AutoDrawObjects" mode. `enable_flag` should be `true` or `false`. If AutoDrawObjects mode is enabled, then all visible objects in the engine will be drawn automatically every update step. If it is not enabled, one can call `ag.drawObjects()` to draw all visible objects in the scene. The AutoDrawObjects mode is initially enabled.

### setAutoEndFrame

`ag.setAutoEndFrame(enable_flag)`

This function sets the "AutoEndFrame" mode. `enable_flag` should be `true` or `false`. If AutoEndFrame mode is enabled, then `ag.endFrame()` will be invoked automatically after executing the update and update_overlay Lua callback functions. The AutoEndFrame mode is initially enabled.

### setAutoPhysics

`ag.setAutoPhysics(enable_flag)`

This function sets the "AutoPhysics" mode. `enable_flag` should be `true` or `false`. If AutoPhysics mode is enabled, then collision detection and physics processing are performed automatically on every update step. If it is not enabled, one can call `ag.doPhysics()` to perform physics updates. The AutoPhysics mode is initially enabled.

### setAutoStartFrame

`ag.setAutoStartFrame(enable_flag)`

This function sets the "AutoStartFrame" mode. `enable_flag` should be `true` or `false`. If AutoStartFrame mode is enabled, then `ag.startFrame()` will be invoked automatically prior to executing the update and update_overlay Lua callback functions. The AutoStartFrame mode is initially enabled.

### setCamera

`ag.setCamera(eye_x, eye_y, eye_z [, center_x, center_y, center_z [, up_x, up_y, up_z] ])`

This function sets the camera position (eye coordinates), focus point (center coordinates), and up vector. If the center coordinates or up vector are not specified, their values are unchanged from the previous invocation of `setCamera()`. The default center point is (0, 0, 0). The default up vector is (0, 0, 1).

### setGravity

`ag.setGravity(gx, gy, gz)`

This function sets the gravity vector to (gx, gy, gz).

### startFrame

`ag.startFrame()`

This function instructs the engine to begin drawing a frame. It is not necessary to call this function if the "AutoStartFrame" mode is enabled. See ag.setAutoStartFrame().

## Object creation functions

The following functions can be used to create "managed" objects. These objects are "managed" by the Lua script (as opposed to having all of their attributes defined in a model file). The properties of managed objects, such as the color, texture, position, and rotation, can be controlled by using the object member methods.

### `createBox`

`obj = ag.createBox(width, depth, height)`

This function creates a managed object which is a box with dimensions given by (width, depth, height). The center of the box is initially located at the origin.

### `createBoxStatic`

`obj = ag.createBoxStatic(width, depth, height)`

Identical to `ag.createBox()` except that the created object is static.

### `createCapsule`

`obj = ag.createCapsule(radius, length)`

This function creates a capsule managed object. A capsule is like a cylinder, but has a half-sphere "capping" each end of the cylinder. `radius` specifies the radius of the cylinder (and caps). `length` specifies the length of the straight part of the capsule (not including the caps). The capsule is oriented with its axis along the Z axis and its center point at the origin.

### `createCapsuleStatic`

`obj = ag.createCapsuleStatic(radius, length)`

Identical to `ag.createCapsule()` except that the created object is static.

### `createPlane`

1) `obj = ag.createPlane(a, b, c, d)`

2) `obj = ag.createPlane(x, y, z, rot_x, rot_y, rot_z)`

The `createPlane()` function creates a managed plane object. All planes are static and are not moved as a result of physics collisions (other objects can still bounce off them). In the four-argument form, the plane is created with equation `ax + by + cz = d`. (a, b, c) specifies the normal vector for the plane. In the six-argument form, the plane is created by specifying a point on the plane, with coordinates (x, y, z), and the Euler rotation angles around the x, y, and z axis. Specifying no rotation would use the default plane normal of (0, 0, 1). If you would like to create a plane by specifying a point on the surface and the surface normal, see the std.createPlanePointNormal() function.

### `createSphere`

`obj = ag.createSphere(radius)`

This function creates a managed sphere object with the radius given. The center of the sphere is initially located at the origin.

### `createSphereStatic`

`obj = ag.createSphereStatic(radius)`

Identical to `ag.createSphere()` except that the created object is static.

## Object member methods

### addForce

`obj:addForce(xf, yf, zf)`

This function adds a one-time force to `obj` with a force vector (xf, yf, zf).

### addForceRel

`obj:addForceRel`

This function adds a one-time force to `obj` with a force vector (xf, yf, zf) which is relative to the local reference frame of `obj`.

### addTorque

`obj:addTorque(xr, yr, zr)`

This function adds torque (a rotational force) to `obj`. The torque vector around global x, y, and z axes is given by (xr, yr, zr).

### addTorqueRel

`obj:addTorqueRel(xr, yr, zr)`

This function adds torque (a rotational force) to `obj`. The torque vector around `obj`'s local x, y, and z axes is given by (xr, yr, zr).

### clone

`new_obj = obj:clone()`

This function makes a copy of the object in the engine. This is more efficient than creating a new object in whatever manner was used to create `obj`. `new_obj` will have all of its own parameters - position, rotation, color, texture, etc... However, these parameter values will be instantiated with the corresponding values from `obj` at the time of cloning. One should call `new_obj:setPosition()` in order to place `new_obj` somewhere where it is not intersecting with other objects in order to pacify the physics engine.

### destroy

`obj:destroy()`

This function destroys the object in the engine. `obj` should not be used after this method is called.

### draw

`obj:draw()`

This function will draw `obj` to the screen. It is called automatically by `ag.drawObjects()`, so calling it is only required if the "AutoDrawObjects" mode is disabled, and `ag.drawObjects()` is not called.

### getAABB

`minx, miny, minz, maxx, maxy, maxz = obj:getAABB()`

This function returns the coordinates of the axis-aligned box bounding `obj`.

### getMass

`mass = obj:getMass()`

This function returns the mass of `obj`.

### getPosition

`x, y, z = obj:getPosition()`

This function returns the coordinates (x, y, z) of the object. Normally, the center-of-mass of the object is located at its local origin. The coordinates of the object's local origin are returned by this call, so these coordinates will be the coordinates of the object's center-of-mass.

### getSize

`sx, sy, sz = obj:getSize()`

This function returns the axis-aligned size of `obj`.

### setColor

`obj:setColor(r, g, b)`

This function sets the color of the object. The parameters correspond to the red, green, and blue components of the object color. Each component should be between 0.0 and 1.0.

### setMass

`obj:setMass(new_mass)`

This function sets the mass of `obj` to `new_mass`.

### setPosition

`obj:setPosition(x, y, z)`

This function sets the coordinates for the object's center-of-mass (local origin) to (x, y, z).

### setRotation

`obj:setRotation(xr, yr, zr)`

This function sets the object's rotation as specified by Euler angles (xr, yr, zr).

### setTexture

`obj:setTexture(tex)`

This function sets the texture of `obj` to `tex`. `tex` should be a Lua reference to a texture loaded with ag.loadTexture().

### setVisible

`obj:setVisible(visible_flag)`

This function sets the visibility of `obj` to `visible_flag`. If `visible_flag` is `true`, then the object will be drawn. Newly created objects are visible by default.

## `std` library

The `std` Lua library supplies a set of Lua functions that may be useful to Lua scripts being executed. It is not imported by default. Import it like this:

    ag.import("std")

### createPlanePointNormal

`obj = std.createPlanePointNormal(x, y, z, nx, ny, nz)`

This function simply wraps `ag.createPlane()` allowing the user to specify a point on the plane with coordinates (x, y, z) and the surface normal of the plane (nx, ny, nz).

### crossProduct

`cp = std.crossProduct(vec1, vec2)`

This function returns the cross product of the two vectors `vec1` and `vec2`. The return value is a Lua array with indices 1 to 3. The indices of `vec1` and `vec2` should be from 1 to 3. This allows specifying a Lua array directly as a parameter to the function. For example:

    local z_axis = std.crossProduct({1, 0, 0}, {0, 1, 0})

### dotProduct

`dp = std.dotProduct(vec1, vec2)`

This function returns the dot product of the two vectors. The indices of `vec1` and `vec2` should be from 1 to 3. This allows specifying a Lua array directly as a parameter to the function.

### pctx

`pixels_x = std.pctx(percent)`

This function returns the number of pixels corresponding to `percent` percent of the screen's X axis. `percent` should be between 0.0 and 1.0.

### pcty

`pixels_y = std.pcty(percent)`

This function returns the number of pixels corresponding to `percent` percent of the screen's Y axis. `percent` should be between 0.0 and 1.0.

## Lua Event Handlers

The following is a list of all events that the Anaglym engine handles:

- `update`
- `update_overlay`
- `key_down`
- `key_up`
- `mousebutton_down`
- `mousebutton_up`
- `mouse_motion`

Lua callback functions may be registered for each of these events.

When a Lua script is loaded, any defined function that matches the name of an engine event with "`_event`" appended will automatically be registered as a callback for that engine event. For example, a function named `key_up_event()` in a loaded Lua script will automatically be registered to receive `key_up` event notifications.

The prototypes for the Lua event handler callback functions follow.

### update

`function update_event()`

This function is called for every frame that is drawn on the screen. It could be called up to a few dozen times per second.

### update_overlay

`function update_overlay_event(width, height)`

This function is called immediately after the `update` function. During this event, the coordinate system is reset from the normal 3D system to a 2D system. The coordinates range from (0, 0) in the lower-left corner of the screen to (width, height) in the upper-right corner of the screen. In this mode, depth testing is disabled, so any graphics drawn will "overlay" whatever is currently on the screen. `width` and `height` contain the size of the Anaglym engine window, in pixels.

### key_down

`function key_down_event(key_name)`

This function is called when a key is initially pressed. `key_name` is a string containing the name of the key pressed. See Key Names for a list of key names.

### key_up

`function key_up_event(key_name)`

This function is called when a key is released. `key_name` is a string containing the name of the key released. See Key Names for a list of key names.

### mousebutton_down

`function mousebutton_down_event(button, x, y)`

This function is called when a mouse button is pressed. `button` contains the number of the button pressed (1: left, 2: middle, 3: right, 4: scroll wheel up, 5: scroll wheel down). The position of the cursor when the mouse button was pressed is at (x, y). This position is only meaningful when the cursor is shown. By default, it is hidden. Cursor visibility can be toggled with the F2 key.

### mousebutton_up

`function mousebutton_up_event(button, x, y)`

This function is called when a mouse button is released. `button` contains the number of the button released (1: left, 2: middle, 3: right, 4: scroll wheel up, 5: scroll wheel down). The position of the cursor when the mouse button was released is at (x, y). This position is only meaningful when the cursor is shown. By default, it is hidden. Cursor visibility can be toggled with the F2 key.

### mouse_motion

`function mouse_motion_event(x, y, xrel, yrel)`

This function is called when the mouse moves. (x, y) specifies the position that the cursor was moved to. This position is only meaningful when the cursor is shown. `xrel` and `yrel` contain the relative movement distance. These values are meaningful regardless of the cursor visibility state.

## Key Names

- `backspace`
- `tab`
- `clear`
- `return`
- `pause`
- `escape`
- `space`
- `exclaim`
- `quotedbl`
- `hash`
- `dollar`
- `ampersand`
- `quote`
- `leftparen`
- `rightparen`
- `asterisk`
- `plus`
- `comma`
- `minus`
- `period`
- `slash`
- `0`
- `1`
- `2`
- `3`
- `4`
- `5`
- `6`
- `7`
- `8`
- `9`
- `colon`
- `semicolon`
- `less`
- `equals`
- `greater`
- `question`
- `at`
- `leftbracket`
- `backslash`
- `rightbracket`
- `caret`
- `underscore`
- `backquote`
- `a`
- `b`
- `c`
- `d`
- `e`
- `f`
- `g`
- `h`
- `i`
- `j`
- `k`
- `l`
- `m`
- `n`
- `o`
- `p`
- `q`
- `r`
- `s`
- `t`
- `u`
- `v`
- `w`
- `x`
- `y`
- `z`
- `delete`
- `kp0`
- `kp1`
- `kp2`
- `kp3`
- `kp4`
- `kp5`
- `kp6`
- `kp7`
- `kp8`
- `kp9`
- `kp_period`
- `kp_divide`
- `kp_multiply`
- `kp_minus`
- `kp_plus`
- `kp_enter`
- `kp_equals`
- `up`
- `down`
- `right`
- `left`
- `insert`
- `home`
- `end`
- `pageup`
- `pagedown`
- `f1`
- `f2`
- `f3`
- `f4`
- `f5`
- `f6`
- `f7`
- `f8`
- `f9`
- `f10`
- `f11`
- `f12`
- `f13`
- `f14`
- `f15`
- `numlock`
- `capslock`
- `scrollock`
- `rshift`
- `lshift`
- `rctrl`
- `lctrl`
- `ralt`
- `lalt`
- `rmeta`
- `lmeta`
- `lsuper`
- `rsuper`
- `mode`
- `compose`
- `help`
- `print`
- `sysreq`
- `break`
- `menu`
- `power`
- `euro`
- `undo`
- `last`