Understanding the Glass Fluid Shader in Three.js

Introduction

Creating realistic visual effects requires understanding the underlying shader logic. The glass fluid shader combines fluid-like displacement with light interaction effects such as fresnel highlights and refraction. This article explains the key aspects of the shader, breaking down its logic and components.

What is a Shader?

Shaders are small programs that run on the GPU. They are responsible for calculating how vertices and fragments (pixels) are rendered. In Three.js, shaders are written in GLSL (OpenGL Shading Language) and are used in ShaderMaterial.

This glass fluid shader includes:

• Vertex Shader: Handles vertex transformations and dynamic displacement.
• Fragment Shader: Manages color and lighting effects for the surface.

Vertex Shader Breakdown

Purpose

The vertex shader controls how the geometry deforms over time to simulate fluid-like movement.

Code Explanation

uniform float time;  // A time variable for animation.
varying vec3 vNormal;  // Pass the surface normal to the fragment shader.
varying vec3 vPosition;  // Pass the vertex position to the fragment shader.

float noise(vec3 p) {
    return sin(p.x + sin(p.y + sin(p.z)));  // Creates a wavy noise effect.
}

void main() {
    vNormal = normalize(normalMatrix * normal);  // Calculate transformed normal.
    vPosition = position;  // Pass original vertex position.

    vec3 pos = position;  // Start with the vertex position.
    float displacement = noise(pos * 2.0 + time * 1.5) * 0.1;  // Apply noise-based displacement.
    pos += normal * displacement;  // Offset vertices along their normals.

    gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);  // Final transformed position.
}

Key Features

1. Noise Function: Introduces a wavy pattern for fluid movement.
2. Displacement: Alters vertex positions dynamically based on noise and time.
3. Animated Effect: The time uniform ensures continuous motion.

Fragment Shader Breakdown

Purpose

The fragment shader controls the surface color, refraction, and fresnel highlights, adding realism to the fluid effect.

Code Explanation

uniform vec3 color1;  // Base fluid color.
uniform vec3 fresnelColor;  // Color of the fresnel highlight.
uniform float refractionStrength;  // Intensity of the refraction effect.
uniform float time;  // Time uniform for animation.
varying vec3 vNormal;  // Interpolated surface normal.
varying vec3 vPosition;  // Interpolated vertex position.

void main() {
    float fresnel = pow(1.0 - abs(dot(normalize(vNormal), normalize(-vPosition))), 3.0);
    // Calculate fresnel effect for edge highlights.

    vec2 refraction = vec2(
        sin(vPosition.y * 3.0 + time) * refractionStrength,
        cos(vPosition.x * 3.0 + time) * refractionStrength
    );
    // Simulate light distortion (refraction) based on position and time.

    vec3 finalColor = mix(color1, fresnelColor, fresnel) + vec3(refraction, 0.0);
    // Blend base color with fresnel effect and add refraction.

    gl_FragColor = vec4(finalColor, 0.15 + fresnel * 0.5);
    // Set the fragment color and adjust transparency dynamically.
}

Key Features

1. Fresnel Effect: Highlights edges based on viewing angle for a glass-like appearance.
2. Refraction Simulation: Creates light distortion to mimic the bending effect of glass.
3. Dynamic Transparency: Adjusts opacity depending on the fresnel intensity.

How It All Comes Together

1. Vertex Shader: Deforms the geometry to look fluid and dynamic.
2. Fragment Shader: Adds realistic lighting, refraction, and color blending.
3. Uniforms: Enable control over animation, color, and effect intensity.

Applications of Glass Fluid Shader

• Water Simulation: For dynamic and reflective water surfaces.
• Abstract Effects: For creative or artistic 3D experiences.
• UI Enhancements: To add futuristic elements to web-based interfaces.

Conclusion

The glass fluid shader demonstrates how a combination of vertex and fragment shaders can create a dynamic and visually captivating effect. By tweaking parameters like noise, color, and refraction strength, you can adapt this shader to a variety of applications. Mastering such shaders opens doors to limitless creative possibilities in Three.js!