#version 330
uniform mat4 VP;
uniform mat4 invVP;
uniform vec2 mouse;
uniform vec2 texStep;
uniform float radius;
uniform vec3 cameraRight;
uniform sampler2D gbufferD;
#ifdef HLSL
uniform sampler2D texa; // direct3d12 unit align
#endif
in vec4 pos;
in vec2 nor;
in vec2 tex;
out vec2 texCoord;
// mat3 rotAxis(vec3 axis, float a) {
// 	float c = cos(a);
// 	vec3 as = axis * sin(a);
// 	mat3 p = mat3(axis.x * axis, axis.y * axis, axis.z * axis);
// 	mat3 q = mat3(c, -as.z, as.y, as.z, c, -as.x, -as.y, as.x, c);
// 	return p * (1.0 - c) + q;
// }
vec3 getPos(vec2 uv) {
	#ifdef HLSL
	float keep = textureLod(texa, vec2(0.0, 0.0), 0.0).r; // direct3d12 unit align
	float keep2 = pos.x + nor.x;
	#endif
	#if defined(HLSL) || defined(METAL)
	float depth = textureLod(gbufferD, vec2(uv.x, 1.0 - uv.y), 0.0).r;
	#else
	float depth = textureLod(gbufferD, uv, 0.0).r;
	#endif
	vec4 wpos = vec4(uv * 2.0 - 1.0, depth * 2.0 - 1.0, 1.0);
	wpos = invVP * wpos;
	return wpos.xyz / wpos.w;
}
vec3 getNormal(vec3 p0, vec2 uv) {
	vec3 p1 = getPos(uv + vec2(texStep.x * 4, 0));
	vec3 p2 = getPos(uv + vec2(0, texStep.y * 4));
	return normalize(cross(p2 - p0, p1 - p0));
}
void createBasis(vec3 normal, out vec3 tangent, out vec3 binormal) {
	tangent = normalize(cameraRight - normal * dot(cameraRight, normal));
	binormal = cross(tangent, normal);
}
void main() {
	texCoord = tex;
	vec3 wpos = getPos(mouse);
	vec2 uv1 = mouse + texStep * 4;
	vec2 uv2 = mouse - texStep * 4;
	vec3 wpos1 = getPos(uv1);
	vec3 wpos2 = getPos(uv2);
	vec3 n = normalize(
		getNormal(wpos, mouse) +
		getNormal(wpos1, uv1) +
		getNormal(wpos2, uv2)
	);
	// float ax = acos(dot(vec3(1,0,0), vec3(n.x,0,0)));
	// float az = acos(dot(vec3(0,0,1), vec3(0,0,n.z)));
	// float sy = -sign(n.y);
	// wpos +=
	// 	rotAxis(vec3(1,0,0), -az * sy + 3.14/2) *
	// 	rotAxis(vec3(0,0,1), ax + 3.14/2) *
	// 	(pos.xyz * radius);
	vec3 n_tan;
	vec3 n_bin;
	createBasis(n, n_tan, n_bin);
	if      (gl_VertexID == 0) wpos += normalize(-n_tan - n_bin) * 0.7 * radius;
	else if (gl_VertexID == 1) wpos += normalize( n_tan - n_bin) * 0.7 * radius;
	else if (gl_VertexID == 2) wpos += normalize( n_tan + n_bin) * 0.7 * radius;
	else if (gl_VertexID == 3) wpos += normalize(-n_tan + n_bin) * 0.7 * radius;
	gl_Position = VP * vec4(wpos, 1.0);
}