skia2/resources/particles/snowfall.json

{
   "MaxCount": 4096,
   "Rate": 30,
   "Life": {
      "min": 10,
      "max": 10
   },
   "StartColor": [ 1, 0.999994, 0.99999, 1 ],
   "EndColor": [ 0.99999, 0.999992, 1, 1 ],
   "Size": {
      "Ranged": true,
      "A0": 10,
      "B0": 10,
      "C0": 10,
      "D0": 0,
      "A1": 10,
      "B1": 0,
      "C1": 0,
      "D1": 0
   },
   "Velocity": {
      "Angle": 1.5708,
      "Spread": 0.174533,
      "Strength": {
         "min": 10,
         "max": 30
      },
      "Bidirectional": false,
      "Spin": {
         "min": 0,
         "max": 0
      },
      "BidirectionalSpin": false
   },
   "Image": "images/half-transparent-white-pixel.png",
   "ImageCols": 1,
   "ImageRows": 1,
   "Emitter": {
      "Type": "SkLineEmitter",
      "P1": { "x": 61, "y": 34 },
      "P2": { "x": 606, "y": 32 }
   },
   "Affectors": [
      {
         "Type": "SkJitterAffector",
         "X": {
            "min": -0.2,
            "max": 0.2
         }
      }
   ]
}
Experimental Particle System This adds a new "Particles" slide to viewer, that allows editing, loading, and saving particle effects. All of the particle system code is in modules/particles. There are many rough edges and some not-yet-finished changes to generalize the model[1]. A rough overview: - SkReflected.h implements a lightweight reflection system for classes derived from SkReflected. Adding a new class involves deriving from SkReflected, adding a macro to the class declaration, and implementing visitFields(), which simply calls a virtual on an SkFieldVisitor for each field. Currently, emitters and affectors use this mechanism. - SkParticleSerialization.h demonstrates two useful field visitors - for serializing to and from JSON. The driver code that uses those is directly in ParticlesSlide. - SkParticleData.h and SkCurve.h define a variety of helper types for talking about particles, both for parameterizing individual values, and communicating about the state of a particle among the effect, affectors, and emitters. - SkParticleEffect.h defines the static data definition of an effect (SkParticleEffectParams), as well as a running instance of an effect (SkParticleEffect). The effect has simple update() and draw() methods. - ParticlesSlide.cpp adds a third field visitor to generate GUIs for interactively editing the running effect. --- 1: The critical change I'd like to make is to remove all special case behavior over time and at spawn (setting sprite frames, size over time, color over time, etc...). Integration is the only fixed function behavior. Everything else is driven by two lists of affectors. One is applied at spawn time, using the effect's lifetime to evaluate curves. This allows spawning particles with different colors as the effect ages out, for example. The second list is applied every frame to update existing particles, and is driven by the particle's lifetime. This allows particles to change color after being spawned, for example. With a small set of affectors using a single expressive curve primitive (keyframed list of cubic curve segments), we can have affectors that update color, size, velocity, position, sprite frame, etc., and implement many complex behaviors. Bug: skia: Change-Id: Id9402bef22825d55d021c5a2f9e5e41791aabaf4 Reviewed-on: https://skia-review.googlesource.com/c/181404 Commit-Queue: Brian Osman <brianosman@google.com> Reviewed-by: Mike Reed <reed@google.com> 2019-02-12 18:27:51 +00:00			`{`
			`"MaxCount": 4096,`
			`"Rate": 30,`
			`"Life": {`
			`"min": 10,`
			`"max": 10`
			`},`
			`"StartColor": [ 1, 0.999994, 0.99999, 1 ],`
			`"EndColor": [ 0.99999, 0.999992, 1, 1 ],`
			`"Size": {`
			`"Ranged": true,`
			`"A0": 10,`
			`"B0": 10,`
			`"C0": 10,`
			`"D0": 0,`
			`"A1": 10,`
			`"B1": 0,`
			`"C1": 0,`
			`"D1": 0`
			`},`
			`"Velocity": {`
			`"Angle": 1.5708,`
			`"Spread": 0.174533,`
			`"Strength": {`
			`"min": 10,`
			`"max": 30`
			`},`
			`"Bidirectional": false,`
			`"Spin": {`
			`"min": 0,`
			`"max": 0`
			`},`
			`"BidirectionalSpin": false`
			`},`
			`"Image": "images/half-transparent-white-pixel.png",`
			`"ImageCols": 1,`
			`"ImageRows": 1,`
			`"Emitter": {`
			`"Type": "SkLineEmitter",`
			`"P1": { "x": 61, "y": 34 },`
			`"P2": { "x": 606, "y": 32 }`
			`},`
			`"Affectors": [`
			`{`
			`"Type": "SkJitterAffector",`
			`"X": {`
			`"min": -0.2,`
			`"max": 0.2`
			`}`
			`}`
			`]`
			`}`