Collidoscope

#include "ParticleController.h"

#include "cinder/Rand.h"

#include <type_traits>

using namespace ci;

using std::list;

ParticleController::ParticleController() :

mNumParticles( 0 )

{

    // uses Cinder (and OpenGL) virtual buffer object based drawing

    // see ParticleSphereCPU example in Cinder library

    mParticles.assign( kMaxParticles, Particle() );

    mParticlePositions.assign( kMaxParticles, vec2( -1, -1 ) );

    mParticleVbo = gl::Vbo::create( GL_ARRAY_BUFFER, mParticlePositions, GL_DYNAMIC_DRAW );

    geom::BufferLayout particleLayout;

    particleLayout.append( geom::Attrib::POSITION, 2, sizeof( vec2 ), 0 );

    auto mesh = gl::VboMesh::create( mParticlePositions.size(), GL_POINTS, { { particleLayout, mParticleVbo } } );

    // creates glsl program to run the batch with

#if ! defined( CINDER_GL_ES )

    auto glsl = gl::GlslProg::create( gl::GlslProg::Format()

        .vertex( CI_GLSL( 150,

            uniform mat4        ciModelViewProjection;

            in vec4                        ciPosition;

            void main( void ) {

                gl_Position = ciModelViewProjection * ciPosition;

                gl_PointSize = 1.0;

            }

            ) )

        .fragment( CI_GLSL( 150,

            out vec4 oColor;

            void main( void ) {

                oColor = vec4( 1.0f, 1.0f, 1.0f, 1.0f );

            }

        ) )

    );

    mParticleBatch = gl::Batch::create( mesh, glsl );

#else

    auto glsl = gl::GlslProg::create( gl::GlslProg::Format()

        .vertex( CI_GLSL( 100,

            uniform mat4        ciModelViewProjection;

            attribute vec4                        ciPosition;

            void main( void ) {

                gl_Position = ciModelViewProjection * ciPosition;

                gl_PointSize = 1.0;

            }

        ) )

        .fragment( CI_GLSL( 100,

            precision highp float;

            void main( void ) {

                gl_FragColor = vec4( 1, 1, 1, 1 );

            }

        ) )

    );

    mParticleBatch = gl::Batch::create( mesh, glsl );

#endif

}

void ParticleController::updateParticles()

{

    // update the positions of the particles and dispose them if they're reached their timespan

    for ( size_t i = 0; i < mNumParticles; i++ ){

        Particle &particle = mParticles[i];

        vec2 &pos = mParticlePositions[i];

        particle.mAge++;

        if ( (!particle.mFlyOver && particle.mAge > particle.mLifespan)

                || (particle.mFlyOver && particle.mAge >= 300) ){

            // dispose particle

            mParticles[i] = mParticles[mNumParticles - 1];

            mParticlePositions[i] = mParticlePositions[mNumParticles - 1];

            mParticlePositions[mNumParticles - 1].x = -1.0f;

            mParticlePositions[mNumParticles - 1].y = -1.0f;

            mNumParticles--;

            continue;

        }

        pos += particle.mVel;

        if ( ci::distance( pos, particle.mCloudCenter ) >  particle.mCloudSize && !particle.mFlyOver ){

            particle.mVel = rotate<float>( particle.mVel, 5 );

        }

    }

    // Copy particle data onto the GPU.

        // Map the GPU memory and write over it.

    void *gpuMem = mParticleVbo->mapReplace();

    memcpy( gpuMem, mParticlePositions.data(), mParticlePositions.size() * sizeof( vec2 ) );

    mParticleVbo->unmap();

}

void ParticleController::addParticles(int amount, const vec2 &initialLocation, const float cloudSize)

{

    // reduce the particles liearly to the total number of particles already present

    // the more particles aleary present the less particle are added

    int reduction = ci::lmap<int>(mNumParticles, 0, kMaxParticles, 0, kMaxParticleAdd);

    amount -= reduction;

    if ( mNumParticles + amount > kMaxParticles ){

                //a.k.a. return if reached kMaxParticles

        amount = kMaxParticles - mNumParticles;

        }

    if( amount <= 0 )

        return;

        for( size_t i = 0; i < amount; i++ ){

        // init new particle

        Particle &particle = mParticles[mNumParticles + i];

        vec2 &pos = mParticlePositions[mNumParticles + i];

        pos = initialLocation + Rand::randVec2() * 5.0f; // find a location nearby the initial location

        particle.mCloudCenter = pos;

        particle.mVel = Rand::randVec2() * Rand::randFloat( 1.0f, 5.0f );

        particle.mCloudSize = cloudSize;

        particle.mAge = 0;

        particle.mLifespan = Rand::randInt( 30, 60 );

        particle.mFlyOver = (Rand::randInt( 500 ) == 0);

        }

    mNumParticles += amount ;

}