2026年1月26日
29 min read
CubistAI Team
TechnologyDiffusion ModelsEducationBasics

How Diffusion Models Work: AI Image Generation Basics

Understand how AI creates images from noise. Simple explanation of diffusion models for non-technical readers.

Published on 2026年1月26日

Ever wondered how typing a few words can produce stunning images? Behind tools like CubistAI, DALL-E, and Midjourney lies a fascinating technology called diffusion models. This guide explains how they work in plain language, no PhD required.

The Magic Behind AI Images

When you type "a cat wearing a space suit on Mars" and receive a detailed image seconds later, you're witnessing diffusion models in action. But what's actually happening?

The Simple Explanation

Imagine you have a clear photograph. Now imagine slowly adding static noise—like TV snow—until the image becomes pure random dots. Diffusion models learn to do this process in reverse: starting from pure noise and gradually removing it to reveal a coherent image.

The "diffusion" name comes from physics, where it describes how particles spread out over time. In AI, we're doing the opposite—starting with spread-out randomness and organizing it into meaning.

How Diffusion Really Works

Step 1: The Forward Process (Training)

During training, the AI learns what happens when you destroy images with noise:

  1. Take millions of real images
  2. Gradually add random noise to each
  3. Record every step of destruction
  4. Create pairs: "image at step X" and "noise added at step X"

This is like teaching someone to clean by showing them exactly how messes are made, step by step.

Step 2: The Reverse Process (Generation)

When you generate an image, the AI runs backwards:

  1. Start with pure random noise (TV static)
  2. Predict what noise to remove
  3. Remove a small amount of predicted noise
  4. Repeat until a clear image emerges

Each removal step is tiny—typically 20-50 steps total—with the image becoming clearer at each stage.

Step 3: Text Guidance

Here's where prompts come in:

  1. Your text is converted into numbers (embeddings)
  2. These numbers guide the noise removal
  3. At each step, the AI asks: "What noise removal would make this more like [your prompt]?"
  4. The image gradually forms to match your description

Visual Walkthrough

From Noise to Image

Alien Desert Landscape

Imagine generating this alien landscape. Here's what happens:

Step 0 (Pure Noise): Random colored dots with no pattern

Step 10: Vague shapes emerge—dark areas, light areas

Step 25: Rough forms visible—horizon line, spherical shapes

Step 40: Details forming—texture on spheres, sky gradients

Step 50 (Final): Complete detailed image with all elements

Each step builds on the previous, like a photograph developing in slow motion.

Key Concepts Simplified

Latent Space

Instead of working with full images (slow and expensive), diffusion models work in "latent space"—a compressed mathematical representation.

Think of it like:

  • Full image = A complete novel
  • Latent space = Detailed chapter summaries

Working with summaries is faster while preserving the essential information.

The U-Net

The core of most diffusion models is a special neural network called U-Net:

  • Named for its U-shaped architecture
  • Takes noisy image → predicts noise to remove
  • Has "skip connections" that preserve details
  • Trained on billions of image examples

Denoising

The actual process of removing noise is called "denoising":

  1. U-Net examines the current noisy state
  2. Considers your text guidance
  3. Predicts which pixels are noise vs. image
  4. Removes estimated noise
  5. Produces slightly cleaner image

This happens dozens of times per generation.

Why Diffusion Models Excel

Advantages Over Previous Methods

Before Diffusion (GANs):

  • Often unstable training
  • Mode collapse (repetitive outputs)
  • Difficult to control

Diffusion Models:

  • Stable, reliable training
  • High diversity in outputs
  • Fine-grained control possible
  • Better quality at high resolutions

Quality Through Iteration

Unlike previous AI that generated images in one shot, diffusion models refine progressively:

  • Early steps: Major composition decisions
  • Middle steps: Structure and shapes
  • Late steps: Fine details and textures

This iterative approach produces more coherent, detailed results.

SDXL: The Technology Behind CubistAI

What Makes SDXL Special

Stable Diffusion XL (SDXL) is the specific diffusion model powering CubistAI. It improves on earlier versions:

Larger Model:

  • More parameters for better understanding
  • Trained on higher resolution images
  • Better text comprehension

Dual Text Encoders:

  • Two separate systems interpret your prompt
  • One captures overall meaning
  • One focuses on specific details
  • Combined for better prompt following

Refinement Stage:

  • Base model creates initial image
  • Refiner model enhances details
  • Two-stage process for quality

SDXL-Lightning

For faster generation, SDXL-Lightning uses "distillation":

  1. Train a smaller model to mimic the full SDXL
  2. Compress 50 steps into 4-8 steps
  3. Maintain most quality at fraction of time

This is why CubistAI can generate images in seconds rather than minutes.

How Your Prompt Becomes an Image

The Journey of a Prompt

Let's trace what happens when you submit a prompt to CubistAI:

1. Text Processing:

Your prompt: "cyberpunk city at night, neon lights, rain"
↓
Tokenized: [cyberpunk] [city] [at] [night] [,] [neon] [lights] [,] [rain]
↓
Embedded: Numbers representing meaning in 768 dimensions

2. Initial Setup:

Random noise generated: Pure static image
Text embeddings attached: Guidance vectors
Parameters set: Resolution, steps, etc.

3. Iterative Denoising:

Step 1: Major shapes influenced by "city" concept
Step 5: Night-time lighting develops
Step 15: Neon colors emerge
Step 25: Rain effects appear
Step 40: Fine details sharpen
Step 50: Final image complete

4. Output:

Latent space decoded back to pixels
Final image displayed to you

Parameters You Can Control

Sampling Steps

More steps generally mean better quality but slower generation:

Steps Speed Quality Best For
4-8 Very Fast Good Quick previews (Lightning)
20-30 Moderate Very Good Standard use
50+ Slow Excellent Maximum quality

CFG Scale

"Classifier-Free Guidance" controls how strictly the AI follows your prompt:

  • Low (1-5): More creative, may ignore prompt
  • Medium (7-9): Balanced, recommended
  • High (12+): Strict following, may reduce quality

Sampling Methods

Different mathematical approaches to the denoising:

  • Euler: Fast, good quality
  • DPM++: Balanced speed and quality
  • DDIM: Deterministic results
  • Ancestral variants: More random variation

The Training Behind It All

Data Requirements

Diffusion models like SDXL trained on:

  • Billions of images from the internet
  • Associated text captions/descriptions
  • Curated for quality and diversity
  • Filtered for content policies

Learning Process

  1. Model sees image + caption pairs
  2. Noise is added at random levels
  3. Model predicts original image from noisy version
  4. Wrong predictions = adjust weights
  5. Repeat billions of times

What the Model Learns

  • Visual concepts (what things look like)
  • Style patterns (artistic techniques)
  • Composition rules (how elements arrange)
  • Text-image relationships (what words mean visually)

Common Misconceptions

"AI Copies Existing Images"

Reality: Diffusion models don't store or retrieve images. They learn patterns and concepts, generating entirely new combinations.

Analogy: A chef who has tasted thousands of dishes doesn't copy recipes—they understand flavor principles and create new dishes.

"More Steps Always = Better"

Reality: Returns diminish after certain points. 30 steps often looks nearly identical to 100 steps.

"AI Understands Images"

Reality: These models learn statistical patterns, not meaning. They don't "understand" that a cat is an animal—they know what pixel patterns associate with the word "cat."

"Prompts Work Like Search"

Reality: You're not searching a database. Each image is generated new, mathematically derived from noise guided by your text.

Technical Deep Dive (Optional)

The Mathematics (Simplified)

The core equation diffusion models solve:

p(x_{t-1}|x_t) = N(x_{t-1}; μ_θ(x_t, t), σ_t²)

In plain terms: "What's the probability distribution of a slightly-less-noisy image, given this noisy image?"

The model learns μ_θ (the mean) through training, predicting where the signal is likely hiding in the noise.

Noise Schedules

How quickly noise is added/removed follows a "schedule":

  • Linear: Constant rate
  • Cosine: Slower start and end
  • Custom: Optimized for specific uses

Different schedules affect generation quality and speed.

Cross-Attention

How text guides image generation:

  1. Image features query text embeddings
  2. Attention weights determine influence
  3. Relevant text concepts guide relevant image regions
  4. "Cat" guides where cat-like features appear

The Future of Diffusion

Current Developments

  • Faster: Fewer steps for same quality
  • Higher resolution: Native 4K and beyond
  • Better control: More precise prompt following
  • Multimodal: Image, video, audio, 3D

Upcoming Capabilities

  • Real-time generation
  • Video diffusion models
  • 3D object generation
  • Interactive editing with AI

Why This Matters

Understanding diffusion models helps you:

  1. Write better prompts: Know what influences results
  2. Choose settings wisely: Understand parameter effects
  3. Set expectations: Know capabilities and limits
  4. Appreciate the technology: Recognize the innovation

Try It Yourself

Experience diffusion models in action with CubistAI:

  • SDXL-Lightning: See fast diffusion in 4 steps
  • Standard SDXL: Compare with 30-step generation
  • Parameter control: Experiment with CFG and steps
  • Free to start: No technical setup needed

Conclusion

Diffusion models represent a fundamental breakthrough in AI image generation:

  • Concept: Learn to reverse the process of adding noise
  • Process: Gradually denoise from random to coherent
  • Guidance: Text embeddings steer the generation
  • Result: New images that never existed before

From random static to stunning artwork, diffusion models transform text into visual reality through elegant mathematics and massive training.

Ready to see diffusion in action? Visit CubistAI and watch your prompts transform into images through the power of diffusion models!


Learn to harness this technology better with our prompt engineering masterclass or explore SDXL-Lightning technology for the fastest generation experience.

Ready to Start Creating?

Now use CubistAI to put the techniques you've learned into practice!