EgoWiki . Documentation . ZippyParticles

"particles" are 2D sprites that move in predictable (read: not scripted) patterns. They may attach to a vertex on a model, fall freely with a starting velocity and a maximum speed of travel, or follow a character limited by turn radius. The sprite graphics may be animated, but individual frames must be taken from a central particle bitmap (at the moment, basicdat/particles.bmp); therefore, the particle frames are all of uniform size, and are numbered from left to right, top to bottom. A final property of particles is that each particle must belong to a single character.

Particles are spawned using shared particle types, which may be created in the following way:

type = PrtType{
   [field = value,]
   -- ...
}

Particles can be spawned using the spawn_particle member function of the Character object. Once spawned, they may be "referenced" using the "ref_particle" function as follows:

ref = ref_particle(order)

"order" is a number specifying how many particles have been spawned since the desired particle was (including the desired particle), and the function returns an object that represents that particle. The following example references the last particle spawned:

ref = ref_particle(1)

Particle references have the following members:

Member	Type	Description
type	particle type	The particle type used to spawn this particle
position	vector?	The position of this particle
velocity	vector?	The velocity of this particle
owner	character	The character that spawned this particle
attached_to	character	The character to which this particle is attached (or nil if it is not)
vertex	number	The index of the grip vertex from which this particle gets its position
target	character	If the particle has a target, this is it
time	number	The number of updates left for this particle
image	number	The index of the current sprite frame
angle	number (degrees)	The direction the particle is facing
in_view	boolean	If non-nil, the particle is currently on the screen
over_tile	number	The index of the tile the particle is above
level	number	The height of the particle
size	number	The current size of the particle
valid	function (no args)	Returns non-nil if the referenced particle is valid. Otherwise, the other fields will not work
kill	function (no args)	Removes the particle from the game

Any of the above fields may be set, but it's usually not useful to do so. If you ever need to set one of the above fields, it will probably be either "position," "owner," or "target."

The fields of the type constructor are described in the table below. Any additional fields will be retained in the type object.

Field	Type	Default	Meaning
render_type	render type	PRTRENDER_LIGHT	The method used for drawing the particle (see #RenderTypes)
image_start	number	0	The starting frame of the particle graphic
frame_rate	number	0	The animation speed in frames per update (0 for no animation)
frames	number	0	The number of frames in the particle animation (or 0 for no animation)
speed	number	0	The maximum speed in map tiles per update
velocity_rand	vector	<0, 0, 0>	A random number is generated for each dimension, and the resulting vector is multiplied with this one component-wise and added to the velocity specified in the particle spawning function to get the initial velocity of each particle of this type
face_velocity	boolean	nil	If non-nil, the particle is rotated to face in the direction of its motion
position_rand	vector	<0, 0, 0>	Same semantics as velocity_rand, but applied to the initial position of the vector
vertex	number [-1, 128]	-1	Default starting vertex (-1 for free motion)
end_on_water	boolean	nil	If non-nil, the particle dies when it hits water
end_on_wall	boolean	nil	If non-nil, the particle dies when it hits a wall
end_on_bump	boolean	nil	If non-nil, the particle dies when it hits a character
end_on_ground	boolean	nil	If non-nil, the particle dies when it hits the ground
end_on_last_frame	boolean	nil	If non-nil, the particle dies when it finishes its animation
end_time	number [-1, infinity]	-1	The lifetime of the particle (-1 for indefinite)
homing (not implemented)	boolean	nil	If non-nil, and if the particle has a target, the particle follows its target
needs_target	boolean	nil	If non-nil, the particle will not spawn without a target
damage (deprecated)
damage_type (deprecated)
is_light	boolean	nil	If non-nil, the particle acts as a light source
light_falloff	number [0, infinity]	0	The distance at which the light source falls off
light_level	number [0, 1]	0	The level of light the particle provides
rotation	range (degrees)	[0, 0]	A rotation rate is chosen randomly from this range
angle	range (degrees)	[0, 0]	A starting angle is chosen randomly from this range
bounce_dampen	number [0, 1]	1	The elasticity of collisions is scaled by this number
air_dampen	number [0, 1]	1	The rate of travel through air is scaled by this number
bump_size	number [0, infinity]	0	The size of the particle for collisions
bump_height	number [0, infinity]	0	The height of the particle for collisions
size	number [0, infinity]	25000	The starting size of the particle
size_add	number	0	How much to add to the size of the particle each update

Render Types

The following table describes the different values for "render_type" in the particle type constructor (screenshots forthcoming):

Value	Meaning
PRTRENDER_SOLID	The particle graphic is drawn directly over the rest of the scene, with no blending
PRTRENDER_TRANS	The particle graphic is blended with the colors in the scene below it
PRTRENDER_LIGHT	The particle graphic has its color values added to those of the scene below it, increasing the brightess of those pixels

-- ElminI - 01 Feb 2004

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