烟花秀：足不出户，纵享视觉盛宴

使用Flutter构建全景烟花表演

烟花秀是农历新年必不可少的活动，它们点亮夜空，营造出欢乐和喜庆的氛围。如果你想在春节期间欣赏烟花秀，又不想出门去人挤人，那么你可以选择在家里观看全景视频。全景视频是一种能够提供360度视角的视频，让你仿佛置身于烟花秀现场。

自定义烟花表演

如果你想自定义烟花表演，那么你可以使用Flutter来创建一个全景视频播放器。Flutter是一个开源的跨平台UI框架，可以让你轻松地构建移动应用、Web应用和桌面应用。

构建全景烟花表演播放器

要使用Flutter构建全景烟花表演播放器，你需要掌握以下知识：

• Flutter基础知识
• Dart编程语言
• OpenGL ES基础知识
• Fragment shader编程

如果你已经掌握了这些知识，那么你可以按照以下步骤来构建全景烟花表演播放器：

1. 创建一个新的Flutter项目。
2. 在项目中添加以下依赖项：

dependencies:
  flutter:
    sdk: flutter

  # OpenGL ES库
  gl: ^0.1.1

  # Fragment shader库
  flutter_fragment_shader: ^0.1.0

3. 在项目中创建一个新的widget，并在其中添加以下代码：

import 'dart:math';
import 'package:flutter/material.dart';
import 'package:gl/gl.dart';
import 'package:flutter_fragment_shader/flutter_fragment_shader.dart';

class FireworksViewer extends StatefulWidget {
  @override
  _FireworksViewerState createState() => _FireworksViewerState();
}

class _FireworksViewerState extends State<FireworksViewer> {
  late FragmentShader fragmentShader;
  late GLFramebuffer framebuffer;
  late GLProgram program;
  late GLBuffer vertexBuffer;
  late GLBuffer indexBuffer;

  final int numParticles = 1000;
  final List<double> particlePositions = [];
  final List<double> particleVelocities = [];
  final List<double> particleColors = [];
  final List<double> particleLifetimes = [];

  @override
  void initState() {
    super.initState();
    fragmentShader = FragmentShader.fromSource(
      """
      #version 300 es

      precision mediump float;

      uniform vec3 u_gravity;
      uniform float u_time;
      uniform sampler2D u_texture;

      varying vec2 v_texcoord;

      void main() {
        // Get the particle's position, velocity, color, and lifetime.
        vec3 position = vec3(particlePositions[gl_VertexID * 3 + 0], particlePositions[gl_VertexID * 3 + 1], particlePositions[gl_VertexID * 3 + 2]);
        vec3 velocity = vec3(particleVelocities[gl_VertexID * 3 + 0], particleVelocities[gl_VertexID * 3 + 1], particleVelocities[gl_VertexID * 3 + 2]);
        vec4 color = vec4(particleColors[gl_VertexID * 4 + 0], particleColors[gl_VertexID * 4 + 1], particleColors[gl_VertexID * 4 + 2], particleColors[gl_VertexID * 4 + 3]);
        float lifetime = particleLifetimes[gl_VertexID];

        // Update the particle's position and velocity.
        position += velocity * u_time;
        velocity += u_gravity * u_time;

        // Update the particle's lifetime.
        lifetime -= u_time;

        // If the particle's lifetime is less than 0, then it is dead.
        if (lifetime <= 0.0) {
          discard;
        }

        // Compute the particle's color.
        color = mix(vec4(1.0, 1.0, 1.0, 1.0), vec4(0.0, 0.0, 0.0, 1.0), lifetime);

        // Set the fragment color.
        gl_FragColor = color;
      }
      """,
    );
    framebuffer = GLFramebuffer.framebufferWithSize(
      width: MediaQuery.of(context).size.width.toInt(),
      height: MediaQuery.of(context).size.height.toInt(),
    );
    program = GLProgram.programWithVertexShaderSourceAndFragmentShaderSource(
      """
      #version 300 es

      uniform mat4 u_projectionMatrix;
      uniform mat4 u_viewMatrix;

      in vec3 a_position;

      void main() {
        gl_Position = u_projectionMatrix * u_viewMatrix * vec4(a_position, 1.0);
      }
      """,
      fragmentShader.source,
    );
    vertexBuffer = GLBuffer.vertexBufferWithFloatArray(particlePositions);
    indexBuffer = GLBuffer.indexBufferWithElementCount(numParticles);

    // Initialize the particle positions, velocities, colors, and lifetimes.
    for (int i = 0; i < numParticles; i++) {
      particlePositions.addAll([
        Random().nextDouble() * 2.0 - 1.0,
        Random().nextDouble() * 2.0 - 1.0,
        Random().nextDouble() * 2.0 - 1.0,
      ]);
      particleVelocities.addAll([
        Random().nextDouble() * 0.1 - 0.05,
        Random().nextDouble() * 0.1 - 0.05,
        Random().nextDouble() * 0.1 - 0.05,
      ]);
      particleColors.addAll([
        Random().nextDouble(),
        Random().nextDouble(),
        Random().nextDouble(),
        1.0,
      ]);
      particleLifetimes.add(Random().nextDouble() * 10.0 + 5.0);
    }

    // Create a new GL context.
    GLContext context = GLContext.useAndCreateContext(framebuffer);

    // Bind the vertex buffer to the attribute variable.
    context.bindBuffer(GL_ARRAY_BUFFER, vertexBuffer.id);
    context.enableVertexAttribArray(program.attributeIndex("a_position"));
    context.vertexAttribPointer(program.attributeIndex("a_position"), 3, GL_FLOAT, false, 0, 0);

    // Bind the index buffer to the element array buffer.
    context.bindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer.id);

    // Set the uniform variables.
    program.use();
    program.setUniformMatrix4fv("u_projectionMatrix", 1, false, perspectiveMatrix);
    program.setUniformMatrix4fv("u_viewMatrix", 1, false, viewMatrix);
    program.setUniform3fv("u_gravity", 1, [0.0, -0.005, 0.0]);
    program.setUniform1f("u_time", 0.0);

    // Draw the particles.
    context.drawElements(GL_TRIANGLES, numParticles, GL_UNSIGNED_INT, 0);

    // Swap the buffers.
    context.swapBuffers();
  }

  @override
  void dispose() {
    super.dispose();
    fragmentShader.dispose();
    framebuffer.dispose();
    program.dispose();
    vertexBuffer.dispose();
    indexBuffer.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Texture(
        textureId: framebuffer.texture.id,
      ),
    );
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _updateFireworks();
  }

  void _updateFireworks() {
    // Create a new GL context.
    GLContext context = GLContext.useAndCreateContext(framebuffer);

    // Bind the vertex buffer to the attribute variable.
    context.bindBuffer(GL_ARRAY_BUFFER, vertexBuffer.id);
    context.enableVertexAttribArray(program.attributeIndex("a_position"));
    context.vertexAttribPointer(program.attributeIndex("a_position"), 3, GL_FLOAT, false, 0, 0);

    // Bind the index buffer to the element array buffer.
    context.bindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer.id);

    // Set the uniform variables.
    program.use();
    program.setUniformMatrix4fv("u_projectionMatrix", 1, false, perspectiveMatrix);
    program.setUniformMatrix4fv("u_viewMatrix", 1, false, viewMatrix);
    program.setUniform3fv("u_gravity", 1, [0.0, -0.005, 0.0]);
    program.setUniform1f