Question 1

Why are GPUs so much faster than CPUs for particle simulations?

Accepted Answer

CPUs are optimized for low-latency sequential computation: a modern CPU has 8–32 cores, each capable of executing complex instruction sequences with branch prediction, out-of-order execution, and large caches. GPUs have thousands of simpler cores optimized for high-throughput parallel computation, sacrificing individual core speed for massive parallelism. A particle simulation updates each particle independently (same equations, different data), which maps perfectly onto GPU parallelism—all particles update simultaneously. For N=1,000,000 particles, a GPU computing 10,000 particles per clock cycle needs 100 passes; a CPU doing them sequentially needs 1,000,000 passes.

Question 2

How does a compute shader work?

Accepted Answer

A compute shader is a GPU program that runs N independent instances (work items) simultaneously, each identified by a unique index. For particle simulation, the compute shader is dispatched with N work items—one per particle. Each work item reads the particle's current position and velocity from a GPU buffer (stored in GPU VRAM), computes forces from neighboring particles or fields, updates velocity and position using an integration scheme (e.g., Verlet or Euler), and writes the result back to the buffer. In the next animation frame, the rendering shader reads these updated positions to draw the particles, while the compute shader is already computing the next timestep.

Question 3

What is the difference between WebGL and WebGPU for particle simulation?

Accepted Answer

WebGL (based on OpenGL ES 2.0/3.0) was designed for rendering and adapts graphics pipeline stages for GPGPU—storing particle data in textures and using fragment shaders to process them. This is somewhat indirect and has limitations (no explicit compute stage, limited memory access patterns). WebGPU is a newer API (available in Chrome/Firefox since 2023) with native compute shader support, more flexible memory access, better debugging tools, and closer alignment with modern GPU capabilities (like Vulkan and Metal). WebGPU enables more efficient GPGPU workloads in-browser, achieving performance closer to native applications.

✨ GPGPU Particle System

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