$input v_normal

/*
 * Copyright 2019 Attila Kocsis. All rights reserved.
 * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause
 */

#include <bgfx_shader.sh>


// this is from 28-wireframe/fs_wf_mesh.sc by Dario Manesku
vec3 evalSh(vec3 _dir)
{
#	define k01 0.2820947918 // sqrt( 1/PI)/2
#	define k02 0.4886025119 // sqrt( 3/PI)/2
#	define k03 1.0925484306 // sqrt(15/PI)/2
#	define k04 0.3153915652 // sqrt( 5/PI)/4
#	define k05 0.5462742153 // sqrt(15/PI)/4

	vec3 shEnv[9];
	shEnv[0] = vec3( 0.967757057878229854,  0.976516067990363390,  0.891218272348969998); /* Band 0 */
	shEnv[1] = vec3(-0.384163503608655643, -0.423492289131209787, -0.425532726148547868); /* Band 1 */
	shEnv[2] = vec3( 0.055906294587354334,  0.056627436881069373,  0.069969936396987467);
	shEnv[3] = vec3( 0.120985157386215209,  0.119297994074027414,  0.117111965829213599);
	shEnv[4] = vec3(-0.176711633774331106, -0.170331404095516392, -0.151345020570876621); /* Band 2 */
	shEnv[5] = vec3(-0.124682114349692147, -0.119340785411183953, -0.096300354204368860);
	shEnv[6] = vec3( 0.001852378550138503, -0.032592784164597745, -0.088204495001329680);
	shEnv[7] = vec3( 0.296365482782109446,  0.281268696656263029,  0.243328223888495510);
	shEnv[8] = vec3(-0.079826665303240341, -0.109340956251195970, -0.157208859664677764);

	vec3 nn = _dir.zxy;

	float sh[9];
	sh[0] =  k01;
	sh[1] = -k02*nn.y;
	sh[2] =  k02*nn.z;
	sh[3] = -k02*nn.x;
	sh[4] =  k03*nn.y*nn.x;
	sh[5] = -k03*nn.y*nn.z;
	sh[6] =  k04*(3.0*nn.z*nn.z-1.0);
	sh[7] = -k03*nn.x*nn.z;
	sh[8] =  k05*(nn.x*nn.x-nn.y*nn.y);

	vec3 rgb = vec3_splat(0.0);
	rgb += shEnv[0] * sh[0] * 1.0;
	rgb += shEnv[1] * sh[1] * 2.0/2.5;
	rgb += shEnv[2] * sh[2] * 2.0/2.5;
	rgb += shEnv[3] * sh[3] * 2.0/2.5;
	rgb += shEnv[4] * sh[4] * 1.0/2.5;
	rgb += shEnv[5] * sh[5] * 0.5;
	rgb += shEnv[6] * sh[6] * 0.5;
	rgb += shEnv[7] * sh[7] * 0.5;
	rgb += shEnv[8] * sh[8] * 0.5;

	return rgb;
}

void main()
{
	vec3 nn = normalize(v_normal);

	gl_FragColor.xyz = evalSh(nn);
	gl_FragColor.w = 1.0;
}