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filament/samples/hybrid_instancing.cpp
Mathias Agopian d7ef6665cc a hybrid instancing sample
2025-07-25 15:03:12 -07:00

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/*
* Copyright (C) 2025 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// -------------------------------------------------------------------------------------------------
// HYBRID INSTANCING SAMPLE
// -------------------------------------------------------------------------------------------------
// This sample demonstrates hybrid instancing, a technique for rendering a large number of
// objects where some transformations are computed on the CPU (per-instance) and others are
// computed on the GPU (per-vertex). It is particularly well-suited for particle systems.
//
// The scene features multiple particle emitters that move in Lissajous patterns. Each emitter
// manages a cloud of small triangle particles. The sample can be switched between two modes:
// - FIREWORKS: Emitters burst all their particles at once on a timer.
// - CONTINUOUS: Emitters continuously emit new particles as old ones die.
//
// The sample also showcases several other Filament features:
// - Dynamic lighting: Each emitter has a colored point light attached to it, which fades
// out with the particles in fireworks mode. A global directional light simulates moonlight.
// - UI controls: A robust ImGui-based UI allows for real-time manipulation of gravity,
// emitter count, particle/emitter freezing, lighting, and emitter modes.
// - Command-line arguments: The camera mode can be set at launch.
// -------------------------------------------------------------------------------------------------
#include "common/arguments.h"
#include <filamentapp/Config.h>
#include <filamentapp/FilamentApp.h>
#include <filament/Camera.h>
#include <filament/Color.h>
#include <filament/Engine.h>
#include <filament/IndexBuffer.h>
#include <filament/InstanceBuffer.h>
#include <filament/LightManager.h>
#include <filament/Material.h>
#include <filament/MaterialEnums.h>
#include <filament/RenderableManager.h>
#include <filament/Scene.h>
#include <filament/Skybox.h>
#include <filament/TransformManager.h>
#include <filament/VertexBuffer.h>
#include <filament/View.h>
#include <camutils/Bookmark.h>
#include <math/mat3.h>
#include <math/mat4.h>
#include <math/vec2.h>
#include <math/vec3.h>
#include <math/vec4.h>
#include <math/norm.h>
#include <utils/EntityManager.h>
#include <utils/Path.h>
#include <getopt/getopt.h>
#include <algorithm>
#include <iostream>
#include <random>
#include <string>
#include <vector>
#include <cmath>
#include <cstddef>
#include <cstdlib>
#include <cstdint>
#include <math.h>
#include <imgui.h>
#include "generated/resources/resources.h"
using namespace filament;
using namespace filament::math;
using utils::Entity;
using utils::EntityManager;
// ------------------------------------------------------------------------------------------------
// App Constants
// ------------------------------------------------------------------------------------------------
// The number of particles in each emitter.
static constexpr uint32_t PARTICLE_COUNT = 64;
// Particle properties
static constexpr float PARTICLE_LIFETIME_MIN = 1.0f;
static constexpr float PARTICLE_LIFETIME_MAX = 3.0f;
static constexpr float PARTICLE_VELOCITY_SCALE = 2.0f;
static constexpr float PARTICLE_ROTATION_SPEED_MIN = M_PI;
static constexpr float PARTICLE_ROTATION_SPEED_MAX = 2.0f * M_PI;
// Emitter properties
static constexpr float EMITTER_FREQUENCY_MIN = 0.5f;
static constexpr float EMITTER_FREQUENCY_MAX = 1.0f;
static constexpr float EMITTER_X_RADIUS_MIN = 2.0f;
static constexpr float EMITTER_X_RADIUS_MAX = 15.0f;
static constexpr float EMITTER_Y_RADIUS_MIN = 2.0f;
static constexpr float EMITTER_Y_RADIUS_MAX = 15.0f;
static constexpr float EMITTER_Z_RADIUS_MIN = 2.0f;
static constexpr float EMITTER_Z_RADIUS_MAX = 10.0f;
static constexpr float EMITTER_PHASE_MAX = 2.0f * M_PI;
// Lighting and Material properties
static constexpr float CONTINUOUS_LIGHT_INTENSITY = 10000.0f;
static constexpr float LIGHT_FALLOFF = 20.0f;
static constexpr float EMISSIVE_FACTOR = 200.0f;
static constexpr float MOONLIGHT_INTENSITY = 100.0f;
// Ground plane properties
static constexpr float GROUND_PLANE_EXTENT = 20.0f;
static constexpr float GROUND_PLANE_Y = -10.0f;
// Camera properties
static constexpr float CAMERA_EXPOSURE_APERTURE = 2.8f;
static constexpr float CAMERA_EXPOSURE_SHUTTER_SPEED = 1.0f / 125.0f;
static constexpr float CAMERA_EXPOSURE_SENSITIVITY = 400.0f;
// UI properties
static constexpr float GRAVITY_STRENGTH_MAX = 2.0f;
static constexpr float FIREWORKS_DELAY_MIN = 0.1f;
static constexpr float FIREWORKS_DELAY_MAX = 10.0f;
static constexpr int EMITTER_COUNT_MIN = 1;
static constexpr int EMITTER_COUNT_MAX = 100;
// ------------------------------------------------------------------------------------------------
// App Data Structures
// ------------------------------------------------------------------------------------------------
// A simple vertex format for our meshes.
struct Vertex {
float2 position;
};
// The mesh for a single particle (a triangle).
static constexpr float PARTICLE_TRIANGLE_SIDE = 0.05f;
static constexpr Vertex TRIANGLE_VERTICES[3] = {
{ { -PARTICLE_TRIANGLE_SIDE, -PARTICLE_TRIANGLE_SIDE / 1.732f } },
{ { PARTICLE_TRIANGLE_SIDE, -PARTICLE_TRIANGLE_SIDE / 1.732f } },
{ { 0.0f, PARTICLE_TRIANGLE_SIDE * 2.0f / 1.732f } },
};
static constexpr uint16_t TRIANGLE_INDICES[3] = { 0, 1, 2 };
// Holds the state of a single particle.
struct Particle {
float3 velocity;
float age = 0.0f;
float lifetime = 0.0f;
float3 rotationAxis;
float rotationSpeed;
float3 birthPosition; // The emitter's position when the particle was born.
};
// Holds the state of a particle emitter, which is a collection of particles and a renderable.
struct Emitter {
Entity renderable;
InstanceBuffer* instanceBuffer = nullptr;
MaterialInstance* materialInstance = nullptr;
std::vector<mat4f> localTransforms;
std::vector<Particle> particles;
// for the emitter's own movement
float3 radii;
float3 frequencies;
float phase;
// for fireworks mode
float timeToBurst = 0.0f;
};
// Holds all the state for this application.
struct App {
enum class EmitterMode { CONTINUOUS, FIREWORKS };
struct UiState {
int emitterCount = 32;
bool particlesFrozen = false;
bool freezeEmitters = false;
EmitterMode emitterMode = EmitterMode::FIREWORKS;
float fireworksDelay = 3.0f;
float gravityStrength = 0.0f;
bool lightsEnabled = true;
bool moonlightEnabled = true;
};
Config config;
UiState ui;
int currentEmitterCount = 0;
bool previousFireworksMode = false;
Skybox* skybox = nullptr;
Material* material = nullptr;
VertexBuffer* vb = nullptr;
IndexBuffer* ib = nullptr;
std::vector<Emitter> emitters;
Scene* scene = nullptr;
double lastTime = 0.0;
Material* groundMaterial = nullptr;
MaterialInstance* groundMi = nullptr;
VertexBuffer* groundVb = nullptr;
IndexBuffer* groundIb = nullptr;
Entity groundPlane;
Entity moonlight;
};
// ------------------------------------------------------------------------------------------------
// Function Declarations
// ------------------------------------------------------------------------------------------------
static void printUsage(char* name);
static int handleCommandLineArguments(int argc, char* argv[], App* app);
static void doUserInterface(App& app);
static void resetParticle(Particle& particle, std::mt19937& gen, const float3& emitterPosition);
static void setupSkybox(Engine& engine, Scene& scene, App& app);
static void setupGroundPlane(Engine& engine, Scene& scene, App& app);
static void setupMoonlight(Engine& engine, Scene& scene, App& app);
static void createEmitterResources(Engine& engine, App& app);
static void createEmitterInstances(Engine& engine, Scene& scene, App& app);
static void setupFireworks(App& app);
static void animateEmitter(Emitter& emitter, TransformManager& tcm, LightManager& lm, double now,
double dt, std::mt19937& gen, const App& app);
// ------------------------------------------------------------------------------------------------
// Main
// ------------------------------------------------------------------------------------------------
int main(int const argc, char** argv) {
App app;
app.config.title = "Hybrid Instancing";
handleCommandLineArguments(argc, argv, &app);
auto setup = [&app](Engine* engine, View* view, Scene* scene) {
app.scene = scene;
setupSkybox(*engine, *scene, app);
setupGroundPlane(*engine, *scene, app);
setupMoonlight(*engine, *scene, app);
createEmitterResources(*engine, app);
createEmitterInstances(*engine, *scene, app);
app.currentEmitterCount = app.ui.emitterCount;
view->getCamera().setExposure(CAMERA_EXPOSURE_APERTURE, CAMERA_EXPOSURE_SHUTTER_SPEED,
CAMERA_EXPOSURE_SENSITIVITY);
view->setPostProcessingEnabled(true);
view->setBloomOptions({ .enabled = true });
};
auto cleanup = [&app](Engine* engine, View*, Scene*) {
// Destroy all the Filament objects that we created.
for (auto const& emitter: app.emitters) {
engine->destroy(emitter.renderable);
engine->destroy(emitter.instanceBuffer);
engine->destroy(emitter.materialInstance);
}
engine->destroy(app.moonlight);
engine->destroy(app.groundPlane);
engine->destroy(app.groundMi);
engine->destroy(app.groundMaterial);
engine->destroy(app.groundVb);
engine->destroy(app.groundIb);
engine->destroy(app.skybox);
engine->destroy(app.material);
engine->destroy(app.vb);
engine->destroy(app.ib);
};
auto animate = [&app](Engine* engine, View*, double const now) {
auto& lm = engine->getLightManager();
// Toggle moonlight
auto const moonlightInstance = lm.getInstance(app.moonlight);
lm.setIntensity(moonlightInstance, app.ui.moonlightEnabled ? MOONLIGHT_INTENSITY : 0.0f);
// Handle emitter count changes from the UI.
if (app.ui.emitterCount != app.currentEmitterCount) {
for (auto const& emitter: app.emitters) {
engine->destroy(emitter.renderable);
engine->destroy(emitter.instanceBuffer);
engine->destroy(emitter.materialInstance);
}
app.emitters.clear();
createEmitterInstances(*engine, *app.scene, app);
app.currentEmitterCount = app.ui.emitterCount;
if (app.ui.emitterMode == App::EmitterMode::FIREWORKS) {
setupFireworks(app);
}
}
// If fireworks mode has just been enabled, set up the emitters for it.
if (app.ui.emitterMode == App::EmitterMode::FIREWORKS &&
app.previousFireworksMode == false) {
setupFireworks(app);
}
app.previousFireworksMode = (app.ui.emitterMode == App::EmitterMode::FIREWORKS);
// Calculate the time delta since the last frame.
double dt = now - app.lastTime;
if (app.lastTime == 0.0) {
dt = 1.0 / 60.0; // First frame
}
app.lastTime = now;
auto& tcm = engine->getTransformManager();
std::mt19937 gen(static_cast<unsigned int>(now * 1000));
// Animate each emitter and its particles.
for (auto& emitter: app.emitters) {
animateEmitter(emitter, tcm, lm, now, dt, gen, app);
}
};
auto imgui = [&app](Engine*, View*) {
doUserInterface(app);
};
FilamentApp::get().animate(animate);
FilamentApp::get().run(app.config, setup, cleanup, imgui);
return 0;
}
// ------------------------------------------------------------------------------------------------
// Helper functions
// ------------------------------------------------------------------------------------------------
// Renders the ImGui UI controls.
void doUserInterface(App& app) {
ImGui::Begin("Controls");
ImGui::SliderInt("Emitters", &app.ui.emitterCount, EMITTER_COUNT_MIN, EMITTER_COUNT_MAX);
ImGui::Checkbox("Freeze Particles", &app.ui.particlesFrozen);
ImGui::BeginDisabled(app.ui.particlesFrozen);
ImGui::Checkbox("Freeze Emitters", &app.ui.freezeEmitters);
ImGui::EndDisabled();
ImGui::SliderFloat("Gravity", &app.ui.gravityStrength, 0.0f, GRAVITY_STRENGTH_MAX, "%.2f G");
ImGui::Checkbox("Enable Lights", &app.ui.lightsEnabled);
ImGui::Checkbox("Moonlight", &app.ui.moonlightEnabled);
bool fireworks = (app.ui.emitterMode == App::EmitterMode::FIREWORKS);
if (ImGui::Checkbox("Fireworks Mode", &fireworks)) {
app.ui.emitterMode = fireworks ? App::EmitterMode::FIREWORKS : App::EmitterMode::CONTINUOUS;
}
if (app.ui.emitterMode == App::EmitterMode::FIREWORKS) {
ImGui::SliderFloat("Delay", &app.ui.fireworksDelay, FIREWORKS_DELAY_MIN,
FIREWORKS_DELAY_MAX);
}
ImGui::End();
}
// Prints command-line usage information.
static void printUsage(char* name) {
const std::string exec_name(utils::Path(name).getName());
std::string usage(
"HYBRID_INSTANCING showcases renderable instancing with instance buffers.\n"
"Usage:\n"
" HYBRID_INSTANCING [options]\n"
"Options:\n"
" --help, -h\n"
" Prints this message\n\n"
" --emitters=<count>, -e <count>\n"
" Sets the number of particle emitters (default: 32)\n\n"
" --camera=<mode>, -c <mode>\n"
" Sets the camera mode: orbit (default), map, or flight\n\n"
"API_USAGE");
const std::string from("HYBRID_INSTANCING");
for (size_t pos = usage.find(from); pos != std::string::npos; pos = usage.find(from, pos)) {
usage.replace(pos, from.length(), exec_name);
}
const std::string apiUsage("API_USAGE");
for (size_t pos = usage.find(apiUsage); pos != std::string::npos;
pos = usage.find(apiUsage, pos)) {
usage.replace(pos, apiUsage.length(), samples::getBackendAPIArgumentsUsage());
}
std::cout << usage;
}
// Parses command-line arguments.
static int handleCommandLineArguments(int const argc, char* argv[], App* app) {
static constexpr const char* OPTSTR = "he:a:c:";
static constexpr option OPTIONS[] = {
{ "help", no_argument, nullptr, 'h' },
{ "api", required_argument, nullptr, 'a' },
{ "emitters", required_argument, nullptr, 'e' },
{ "camera", required_argument, nullptr, 'c' },
{ nullptr, 0, nullptr, 0 } };
int opt;
int option_index = 0;
while ((opt = getopt_long(argc, argv, OPTSTR, OPTIONS, &option_index)) >= 0) {
const std::string arg(optarg ? optarg : "");
switch (opt) {
default:
case 'h':
printUsage(argv[0]);
exit(0);
case 'a':
app->config.backend = samples::parseArgumentsForBackend(arg);
break;
case 'e':
app->ui.emitterCount = atoi(arg.c_str());
break;
case 'c':
if (arg == "flight") {
app->config.cameraMode = camutils::Mode::FREE_FLIGHT;
} else if (arg == "orbit") {
app->config.cameraMode = camutils::Mode::ORBIT;
} else if (arg == "map") {
app->config.cameraMode = camutils::Mode::MAP;
} else {
std::cerr << "Unrecognized camera mode. Must be 'flight' | 'orbit' | 'map'."
<< std::endl;
}
break;
}
}
return optind;
}
// Resets a particle to a new random state.
static void resetParticle(Particle& particle, std::mt19937& gen, const float3& emitterPosition) {
std::uniform_real_distribution vel_dist(-1.0f, 1.0f);
std::uniform_real_distribution life_dist(PARTICLE_LIFETIME_MIN, PARTICLE_LIFETIME_MAX);
std::uniform_real_distribution rot_speed_dist(PARTICLE_ROTATION_SPEED_MIN,
PARTICLE_ROTATION_SPEED_MAX);
particle.velocity = normalize(float3{ vel_dist(gen), vel_dist(gen), vel_dist(gen) }) *
PARTICLE_VELOCITY_SCALE;
particle.age = 0.0f;
particle.lifetime = life_dist(gen);
particle.rotationAxis = normalize(float3{ vel_dist(gen), vel_dist(gen), vel_dist(gen) });
particle.rotationSpeed = rot_speed_dist(gen);
particle.birthPosition = emitterPosition;
}
// Creates a simple skybox with a solid color.
void setupSkybox(Engine& engine, Scene& scene, App& app) {
app.skybox = Skybox::Builder().color({ 0.1, 0.125, 0.25, 1.0 }).build(engine);
scene.setSkybox(app.skybox);
}
// Creates a ground plane to receive shadows.
void setupGroundPlane(Engine& engine, Scene& scene, App& app) {
app.groundMaterial = Material::Builder()
.package(RESOURCES_AIDEFAULTMAT_DATA, RESOURCES_AIDEFAULTMAT_SIZE)
.build(engine);
app.groundMi = app.groundMaterial->createInstance();
app.groundMi->setParameter("baseColor", RgbType::LINEAR, float3{ 0.8f });
app.groundMi->setParameter("metallic", 0.0f);
app.groundMi->setParameter("roughness", 0.8f);
const static float3 GROUND_VERTICES[4] = {
{ -GROUND_PLANE_EXTENT, 0, -GROUND_PLANE_EXTENT },
{ -GROUND_PLANE_EXTENT, 0, GROUND_PLANE_EXTENT },
{ GROUND_PLANE_EXTENT, 0, GROUND_PLANE_EXTENT },
{ GROUND_PLANE_EXTENT, 0, -GROUND_PLANE_EXTENT },
};
short4 const tbn = packSnorm16(
mat3f::packTangentFrame(
mat3f{
float3{ 1.0f, 0.0f, 0.0f },
float3{ 0.0f, 0.0f, 1.0f },
float3{ 0.0f, 1.0f, 0.0f }
}
).xyzw);
const static short4 GROUND_TANGENTS[]{ tbn, tbn, tbn, tbn };
app.groundVb = VertexBuffer::Builder()
.vertexCount(4)
.bufferCount(2)
.attribute(POSITION, 0, VertexBuffer::AttributeType::FLOAT3, 0, sizeof(float3))
.attribute(TANGENTS, 1, VertexBuffer::AttributeType::SHORT4, 0, sizeof(short4))
.normalized(TANGENTS)
.build(engine);
app.groundVb->setBufferAt(engine, 0, { GROUND_VERTICES, sizeof(GROUND_VERTICES) });
app.groundVb->setBufferAt(engine, 1, { GROUND_TANGENTS, sizeof(GROUND_TANGENTS) });
static constexpr uint16_t GROUND_INDICES[6] = { 0, 1, 2, 2, 3, 0 };
app.groundIb = IndexBuffer::Builder()
.indexCount(6)
.bufferType(IndexBuffer::IndexType::USHORT)
.build(engine);
app.groundIb->setBuffer(engine, { GROUND_INDICES, sizeof(GROUND_INDICES) });
app.groundPlane = EntityManager::get().create();
RenderableManager::Builder(1)
.boundingBox({ { 0, 0, 0 },
{ GROUND_PLANE_EXTENT * 2.0f, 0.01, GROUND_PLANE_EXTENT * 2.0f } })
.material(0, app.groundMi)
.geometry(0, RenderableManager::PrimitiveType::TRIANGLES, app.groundVb, app.groundIb)
.culling(false)
.receiveShadows(true)
.castShadows(false)
.build(engine, app.groundPlane);
scene.addEntity(app.groundPlane);
auto& tcm = engine.getTransformManager();
auto const groundInstance = tcm.getInstance(app.groundPlane);
tcm.setTransform(groundInstance, mat4f::translation(float3{ 0.0f, GROUND_PLANE_Y, 0.0f }));
}
// Creates a directional light to simulate moonlight.
void setupMoonlight(Engine& engine, Scene& scene, App& app) {
app.moonlight = EntityManager::get().create();
LightManager::Builder(LightManager::Type::DIRECTIONAL)
.color(Color::toLinear<ACCURATE>(sRGBColor(0.8f, 0.9f, 1.0f)))
.intensity(MOONLIGHT_INTENSITY)
.direction(normalize(float3{ 0.5f, -1.0f, -0.7f }))
.castShadows(false)
.build(engine, app.moonlight);
scene.addEntity(app.moonlight);
}
// Creates resources that are shared among all emitters.
void createEmitterResources(Engine& engine, App& app) {
app.vb = VertexBuffer::Builder()
.vertexCount(3)
.bufferCount(1)
.attribute(POSITION, 0, VertexBuffer::AttributeType::FLOAT2, 0, sizeof(Vertex))
.build(engine);
app.vb->setBufferAt(engine, 0, { TRIANGLE_VERTICES, sizeof(TRIANGLE_VERTICES) });
app.ib = IndexBuffer::Builder()
.indexCount(3)
.bufferType(IndexBuffer::IndexType::USHORT)
.build(engine);
app.ib->setBuffer(engine, { TRIANGLE_INDICES, sizeof(TRIANGLE_INDICES) });
app.material = Material::Builder()
.package(RESOURCES_SANDBOXUNLIT_DATA, RESOURCES_SANDBOXUNLIT_SIZE)
.build(engine);
}
// Creates the particle emitters and their associated Filament resources.
void createEmitterInstances(Engine& engine, Scene& scene, App& app) {
std::mt19937 gen(0); // Standard mersenne_twister_engine seeded with 0
std::uniform_real_distribution fdist(EMITTER_FREQUENCY_MIN, EMITTER_FREQUENCY_MAX);
std::uniform_real_distribution xdist(EMITTER_X_RADIUS_MIN, EMITTER_X_RADIUS_MAX);
std::uniform_real_distribution ydist(EMITTER_Y_RADIUS_MIN, EMITTER_Y_RADIUS_MAX);
std::uniform_real_distribution zdist(EMITTER_Z_RADIUS_MIN, EMITTER_Z_RADIUS_MAX);
std::uniform_real_distribution pdist(0.0f, EMITTER_PHASE_MAX);
std::uniform_real_distribution cdist(0.0f, 1.0f);
for (int i = 0; i < app.ui.emitterCount; ++i) {
Emitter emitter;
emitter.instanceBuffer = InstanceBuffer::Builder(PARTICLE_COUNT).build(engine);
emitter.materialInstance = app.material->createInstance();
emitter.localTransforms.resize(PARTICLE_COUNT, mat4f(1.0f));
emitter.particles.resize(PARTICLE_COUNT);
const LinearColor color{ cdist(gen), cdist(gen), cdist(gen) };
emitter.materialInstance->setParameter("baseColor", RgbType::LINEAR, color);
emitter.materialInstance->
setParameter("emissive", RgbType::LINEAR, color * EMISSIVE_FACTOR);
emitter.materialInstance->setCullingMode(MaterialInstance::CullingMode::NONE);
for (auto& p: emitter.particles) {
resetParticle(p, gen, { 0.0f, 0.0f, 0.0f });
}
emitter.renderable = EntityManager::get().create();
RenderableManager::Builder(1)
.boundingBox({ { 0, 0, 0 }, { 6, 6, 6 } })
.material(0, emitter.materialInstance)
.geometry(0, RenderableManager::PrimitiveType::TRIANGLES, app.vb, app.ib)
.instances(PARTICLE_COUNT, emitter.instanceBuffer)
.culling(false)
.castShadows(false)
.build(engine, emitter.renderable);
LightManager::Builder(LightManager::Type::POINT)
.color(color)
.intensity(CONTINUOUS_LIGHT_INTENSITY)
.falloff(LIGHT_FALLOFF)
.castShadows(false)
.build(engine, emitter.renderable);
scene.addEntity(emitter.renderable);
emitter.radii = { xdist(gen), ydist(gen), zdist(gen) };
emitter.frequencies = { fdist(gen), fdist(gen), fdist(gen) };
emitter.phase = pdist(gen);
app.emitters.push_back(emitter);
}
}
// Sets up the initial state for fireworks mode.
void setupFireworks(App& app) {
for (int i = 0; i < app.emitters.size(); ++i) {
auto& emitter = app.emitters[i];
emitter.timeToBurst = (float(i) / float(app.emitters.size())) * app.ui.fireworksDelay;
for (auto& p: emitter.particles) {
// Make particles "dead" until the first burst.
p.age = 1e6f;
}
}
}
// Animates a single emitter and its particles.
void animateEmitter(Emitter& emitter, TransformManager& tcm, LightManager& lm, double now,
double dt, std::mt19937& gen, const App& app) {
// If particles are frozen, skip all updates for this emitter.
// This also effectively freezes the emitter's movement.
if (app.ui.particlesFrozen) {
return;
}
// Animate the emitter's transform (a Lissajous curve)
auto emitterInstance = tcm.getInstance(emitter.renderable);
float3 emitter_pos;
if (!app.ui.freezeEmitters) {
const float t = float(now) * 0.5f + emitter.phase;
emitter_pos = { emitter.radii.x * std::sin(emitter.frequencies.x * t),
emitter.radii.y * std::sin(emitter.frequencies.y * t),
emitter.radii.z * std::cos(emitter.frequencies.z * t) };
tcm.setTransform(emitterInstance, mat4f::translation(emitter_pos));
} else {
emitter_pos = tcm.getTransform(emitterInstance)[3].xyz;
}
// Update the light's intensity.
auto lightInstance = lm.getInstance(emitter.renderable);
if (!app.ui.lightsEnabled) {
lm.setIntensity(lightInstance, 0.0f);
} else {
if (app.ui.emitterMode == App::EmitterMode::FIREWORKS) {
// Fade the light's intensity with the age of the particles.
const auto& p = emitter.particles[0];
const float scale = std::max(0.0f, 1.0f - (p.age / p.lifetime));
lm.setIntensity(lightInstance, CONTINUOUS_LIGHT_INTENSITY * scale);
} else {
// In continuous mode, the light has a constant intensity.
lm.setIntensity(lightInstance, CONTINUOUS_LIGHT_INTENSITY);
}
}
// In fireworks mode, check if it's time for a burst.
if (app.ui.emitterMode == App::EmitterMode::FIREWORKS) {
emitter.timeToBurst -= float(dt);
if (emitter.timeToBurst <= 0.0f) {
// Time to burst! Reset all particles.
for (auto& p: emitter.particles) {
resetParticle(p, gen, emitter_pos);
}
// Reset timer for the next burst.
emitter.timeToBurst += app.ui.fireworksDelay;
}
}
// Animate particles relative to the emitter
for (uint32_t i = 0; i < PARTICLE_COUNT; ++i) {
auto& p = emitter.particles[i];
p.age += float(dt);
// In continuous mode, reset particles when their lifetime expires.
if (app.ui.emitterMode == App::EmitterMode::CONTINUOUS) {
if (p.age > p.lifetime) {
resetParticle(p, gen, emitter_pos);
}
}
// If the particle is alive, compute its transform. Otherwise, make it invisible.
if (p.age <= p.lifetime) {
const float scale = std::max(0.0f, 1.0f - (p.age / p.lifetime));
float3 particle_travel = p.velocity * p.age;
if (app.ui.gravityStrength > 0.0f) {
constexpr float3 g = { 0.0f, -9.8f, 0.0f };
particle_travel += 0.5f * g * app.ui.gravityStrength * p.age * p.age;
}
const float3 particle_pos = p.birthPosition - emitter_pos + particle_travel;
const mat4f rotation = mat4f::rotation(p.age * p.rotationSpeed, p.rotationAxis);
emitter.localTransforms[i] =
mat4f::translation(particle_pos) * rotation * mat4f::scaling(scale);
} else {
emitter.localTransforms[i] = mat4f::scaling(0.0f);
}
}
emitter.instanceBuffer->setLocalTransforms(emitter.localTransforms.data(), PARTICLE_COUNT);
}
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