Cavity / Curvature Shader
N
Nathan
Blenders cavity shader is beautiful and helpful in clarifying forms to the eye.
Plasticity would really benefit from this, especially when viewing without wireframe. I think it would be a nice in both matcap and render views.
I looked into how this might be implemented and found this lovely shader
// License: CC0 (http://creativecommons.org/publicdomain/zero/1.0/)
#extension GL_OES_standard_derivatives : enable
varying vec3 normal;
varying vec3 vertex;
void main() {
vec3 n = normalize(normal);
// Compute curvature
vec3 dx = dFdx(n);
vec3 dy = dFdy(n);
vec3 xneg = n - dx;
vec3 xpos = n + dx;
vec3 yneg = n - dy;
vec3 ypos = n + dy;
float depth = length(vertex);
float curvature = (cross(xneg, xpos).y - cross(yneg, ypos).x) * 4.0 / depth;
// Compute surface properties
vec3 light = vec3(0.0);
vec3 ambient = vec3(curvature + 0.5);
vec3 diffuse = vec3(0.0);
vec3 specular = vec3(0.0);
float shininess = 0.0;
// Compute final color
float cosAngle = dot(n, light);
gl_FragColor.rgb = ambient +
diffuse * max(0.0, cosAngle) +
specular * pow(max(0.0, cosAngle), shininess);
}