glsl-face-normal

(click for demo)

Approximates face normals in the fragment shader for flat shading from the position in camera space.

Note: You need to enable GL_OES_standard_derivatives.

Fragment:

#extension GL_OES_standard_derivatives : enable
varying vec3 vViewPos;
 
#pragma glslify: faceNormal = require('glsl-face-normal') 
 
void main() {
  vec3 normal = faceNormal(vViewPos);
  //... lighting 
}

Vertex:

varying vec3 vViewPos;
 
void main() {
  vec4 pos = vec4(position, 1.0);
  vec4 mpos = modelViewMatrix * pos;
  gl_Position = projectionMatrix * mpos;
  vViewPos = -mpos.xyz;
}

Usage

vec3 normal = faceNormal(vec3 pos)

Approximates the face normal from the given pos, which is typically the position in camera-space.

For better precision, you can use the eye relative position instead.

License

MIT. See LICENSE.md for details.