Overview
Animate an explosion of many particles.
dotsDrawableExplosion simulates a fireworks-style explosion. It animates multiple particles with constant-acceleration projectile motion. The animation has a few distinct phases:
- Explosion. Animates many particles until they hit the ground. The particles start with random velocities, which are be chosen so that the eventual resting positions will obey a given distribution. Each particle is drawn as a point.
- Bounces. Animates the particles as they bounce off the ground. The bounce trajectories follow from the explosion trajectories, with damping at each contact with the ground. There are 4 bounces.
- Rest. After all the bounces are complete, each particle settles in place at ground level.
The explosion and bounce trajectory parameters for each particle are solved during prepareToDrawInWindow(). Frame-by-frame positions are computed for each particle during draw(), based on the current time. An OpenGL vertex shader (explosion.vert by default) implements the projectile calculations.
The algebra used to solve trajectory parameters is on the Snow Dots wiki: http://code.google.com/p/snow-dots/wiki/ExplosionAlgebra
Inheritance diagram for dotsDrawableExplosion:
Properties and Events | |
| Property | vertexShader = 'explosion.vert' |
| file name with projectile motion vertex shader source | |
| Property | xRest = 1 |
| x-position where each particle should come to rest | |
| Property | yRest = 1 |
| y-position where each particle should bounce, then rest | |
| Property | tRest = 1 |
| how long it should take each particle to come to rest | |
| Property | gravity = -1 |
| constant vertical acceleration for all particles | |
| Property | bounceDamping = [0.5 -0.5] |
| multiplier for particle x and y velocity at each bounce [bX bY] | |
| Property | whichRoot = 2 |
| how to choose roots from quadratic solutions More... | |
| Property | clockFunction |
| function that returns the current time as a number | |
| Property | currentTime |
| time of the most recent draw() | |
| Property | isInternalTime = true |
| whether to update currentTime with clockFunction during draw() | |
 Properties and Events inherited from dotsDrawableVertices | |
| Property | x = 0 |
| vertex x-positions (x, y, and z must be scalar or match sizes) | |
| Property | y = 0 |
| vertex y-positions (x, y, and z must be scalar or match sizes) | |
| Property | z = 0 |
| vertex z-positions (x, y, and z must be scalar or match sizes) | |
| Property | colors = [1 1 1] |
| color map to use for vertices [r g b a; r g b a; etc. More... | |
| Property | isColorByVertexGroup = false |
| whether to color vertices in groups(true) or individually(false) | |
| Property | indices = [] |
| array of indices for selecting, reusing, and reordering vertices More... | |
| Property | pixelSize = 1 |
| width in pixels for points or lines | |
| Property | isSmooth = false |
| whether to use anti-aliasing for primitives | |
| Property | primitive = 0 |
| index to choose OpenGL vertex drawing mode More... | |
| Property | usageHint = 3 |
| index to choose usage "hint" for OpenGL buffers More... | |
| Property | translation = [] |
| optional translation to apply to vertex positions [tX tY tZ] More... | |
| Property | rotation = [] |
| optional rotation of vertices about coordinate axes [rX rY rZ] More... | |
| Property | scaling = [] |
| optional scaling to apply to vertex positions [sX sY sZ] More... | |
| Properties and Events inherited from dotsDrawable | |
| Property | isVisible = true |
| true or false, whether to draw() this object | |
Protected Properties | |
| Property | startTime |
| zero-time for the beginning of each animation sequence | |
| Property | programInfo |
| identifier and other info for OpenGL shader program | |
| Property | timeVar |
| identifier and other info about the shader time variable | |
| Property | nBounces = 4 |
| number of bounces supported by shader program | |
| attribNames | |
| attribute names for the OpenGL shader program | |
| Property | attribData |
| attribute data calculated in solveParticleSystem() | |
| Protected Properties inherited from dotsDrawableVertices | |
| Property | attribBufferInfo = [] |
| identifier and other info for the OpenGL vertex attribute buffer | |
| Property | isAttribBufferStale = true |
| whether or not the attribute buffer is out of date | |
| Property | indexBufferInfo = [] |
| identifier and other info for the OpenGL vertex index buffer | |
| Property | isIndexBufferStale = true |
| whether or not the index buffer is out of date | |
| Property | colorBufferInfo = [] |
| identifier and other info for the OpenGL vertex color buffer | |
| Property | isColorBufferStale = true |
| whether or not the color buffer is out of date | |
| Property | smoothMap |
| map primitive integers to dotsMglSmoothness() switches | |
Methods | |
| self | dotsDrawableExplosion () |
| Constructor takes no arguments. | |
| delete (self) | |
| Release OpenGL resources. | |
| set_xRest (self, xRest) | |
| Keep track of required buffer updates. | |
| set_yRest (self, yRest) | |
| Keep track of required buffer updates. | |
| set_tRest (self, tRest) | |
| Keep track of required buffer updates. | |
| set_bounceDamping (self, bounceDamping) | |
| Keep track of required buffer updates. | |
| set_gravity (self, gravity) | |
| Keep track of required buffer updates. | |
| set_whichRoot (self, whichRoot) | |
| Keep track of required buffer updates. | |
| tRestMins | calculateMinimumRestTimes (self) |
| Determine minimum resting times, based on system properties. More... | |
| solveParticleSystem (self) | |
| Compute motion parameters for each particle and each bounce. | |
| prepareToDrawInWindow (self) | |
| Solve particle trajectores into buffers and load shader program. | |
| draw (self) | |
| Draw particles, based on the current time. | |
| nVertices | getNVertices (self) |
| Calculate number of vertices based on several properties;. | |
| Methods inherited from dotsDrawableVertices | |
| self | dotsDrawableVertices () |
| Constructor takes no arguments. | |
| delete (self) | |
| Release OpenGL resources. More... | |
| set_x (self, x) | |
| Keep track of required buffer updates. | |
| set_y (self, y) | |
| Keep track of required buffer updates. | |
| set_z (self, z) | |
| Keep track of required buffer updates. | |
| set_indices (self, indices) | |
| Keep track of required buffer updates. | |
| set_colors (self, colors) | |
| Keep track of required buffer updates. | |
| set_isColorByVertexGroup (self, isColorByVertexGroup) | |
| Keep track of required buffer updates. | |
| nVertices | getNVertices (self) |
| Calculate number of vertices from x, y, and z. | |
| prepareToDrawInWindow (self) | |
| Create fresh OpenGL buffer objects. | |
| draw (self) | |
| Draw vertices from OpenGL buffer objects. | |
| Methods inherited from dotsDrawable | |
| self | dotsDrawable () |
| Constructor takes no arguments. | |
| prepareToDrawInWindow (self) | |
| Do any pre-draw setup that requires an OpenGL drawing window. | |
| mayDrawNow (self) | |
| Draw() or not, depending on isVisible and possibly other factors. | |
| draw (self) | |
| Subclass must redefine draw() to draw graphics. | |
| show (self) | |
| Shorthand to set isVisible=true. | |
| hide (self) | |
| Shorthand to set isVisible=false. | |
Protected Methods | |
| deleteAttribBuffer (self) | |
| Release OpenGL vertex buffer for each attribNames. | |
| updateAttribBuffer (self) | |
| Write OpenGL vertex buffer data for each attribNames. | |
| loadShaderProgram (self) | |
| Load the shader program which makes particles explode. | |
| selectBuffers (self) | |
| Bind buffers for drawing. | |
| deselectBuffers (self) | |
| Unbind buffers for drawing. | |
| Protected Methods inherited from dotsDrawableVertices | |
| deleteBuffers (self) | |
| Release OpenGL buffer handles and memory. | |
| updateBuffers (self) | |
| Write attribute, color, and index data to buffers, as needed. | |
| deleteAttribBuffer (self) | |
| Release OpenGL vertex attribute resources. | |
| updateAttribBuffer (self) | |
| Write new vertex attributes to OpenGL buffer(s). | |
| deleteIndexBuffer (self) | |
| Release OpenGL vertex index resources. | |
| updateIndexBuffer (self) | |
| Write new vertex indices to OpenGL buffer(s). | |
| deleteColorBuffer (self) | |
| Release OpenGL vertex color resources. | |
| updateColorBuffer (self) | |
| Write new vertex colors to OpenGL buffer(s). | |
| groupIndices | getVertexGroupIndices (self) |
| Get an arbitrary 1-based group index for each vertex. | |
| buffer | overwriteOrReplaceBuffer (self, oldBuffer, data, target, elementsPerVertex) |
| Modify or replace a buffer with new data. | |
| selectBuffers (self) | |
| Bind buffers for drawing. | |
| deselectBuffers (self) | |
| Unbind buffers for drawing. | |
| flagAllBuffersAsStale (self) | |
| Mark all OpenGL buffers as stale. | |
Static Methods | |
| static roots | solveQuadratic (aCoef, bCoef, cCoef) |
| Solve roots of a quadratic, given coefficients. | |
| Static Methods inherited from dotsDrawable | |
| static frameInfo | drawFrame (drawables, doClear) |
| draw() several drawable objects and show the next Screen frame. More... | |
| static ensemble | makeEnsemble (name, objects) |
| Convenient utility for combining a bunch of drawables into an ensemble. More... | |
| static frameInfo | drawEnsemble (ensemble, args, prepareFlag, showDuration, pauseDuration) |
| Convenient utility for drawing an ensemble either locally or remotely. More... | |
Methods
◆ calculateMinimumRestTimes()
| tRestMins calculateMinimumRestTimes | ( | self | ) |
Determine minimum resting times, based on system properties.
Several parameters affect how long each particle requires to fall to the ground and bounce. Together they impose a minimum duration for particle bouncing. Smaller times for tRest would be impossible to achieve.
Intuituvely, a particle starting with zero y-velocity should require the least time–adding upward or downward velocity would add energy to the system and causes larger bounces. calculateMinimumRestTimes() assumes zero starting velocity and calculates the corresponding time to complete all bounces.
Properties and Events
◆ whichRoot
| Property whichRoot = 2 |
how to choose roots from quadratic solutions
Solving for velocities yields two solutions. The first tends to slam paricles against the ground and makes them bounce high. The second tends to toss particles gently in the air. Either way, particles end up in the same place.
The documentation for this class was generated from the following file:
- dotsDrawableExplosion.m
