ShellTexturing.gdshader

shader_type spatial;

uniform float shell_index;
uniform float shell_count;
uniform float frond_count;
uniform vec3 light_pos;
uniform float thickness;
uniform vec3 color;
uniform float height;

float random( vec2 p ) {
	// from https://stackoverflow.com/questions/5149544/can-i-generate-a-random-number-inside-a-pixel-shader
    vec2 K1 = vec2(
        23.14069263277926, // e^pi (Gelfond's constant)
        2.665144142690225 // 2^sqrt(2) (Gelfond–Schneider constant)
    );
    return fract( cos( dot(p,K1) ) * 12345.6789 );
}

void vertex() {
	float h = shell_index / shell_count;
	h = pow(h, 2);
	VERTEX += NORMAL * h * height;
	VERTEX.x += (cos(TIME * 1.5 - VERTEX.y) + sin(TIME - VERTEX.y) + 1.0) * pow(h, 2) * 0.05;
}

void fragment() {
	vec2 newUV = UV * frond_count;
	vec2 seedCoord = floor(newUV);
	vec2 localUV = fract(newUV) * 2.0 - 1.0;
	float distToCentre = length(localUV);
	
	float h = shell_index / shell_count;
	float rand = random(seedCoord);
	
	if ( distToCentre > thickness * (rand - h) && shell_index > 0.0 ) discard;
	
	float ndotl = clamp(dot(NORMAL, light_pos), 0, 1) * 0.5 + 0.5;
	ndotl = ndotl * ndotl;
	
	float ambientOcclusion = pow(h, 2.0);
	ambientOcclusion += 0.5;
	ambientOcclusion = clamp(ambientOcclusion, 0, 1);
	
	ALBEDO = color * ndotl * ambientOcclusion;
}