#[set(everything)]
const constants: {
	VP: float4x4;
	invVP: float4x4;
	mouse: float2;
	tex_step: float2;
	radius: float;
	camera_right: float3;
	opacity: float;
	angle: float2;
	scale_x: float;
	camera_up: float3;
	camera_align: float;
};

#[set(everything)]
const sampler_linear: sampler;

#[set(everything)]
const gbufferD: tex2d;

#[set(everything)]
const texdecal: tex2d;

#[set(everything)]
const gbuffer0: tex2d;

struct vert_in {
	pos: float4;
	nor: float2;
	tex: float2;
}

struct vert_out {
	pos: float4;
	tex: float2;
}

fun get_pos(uv: float2): float3 {
	var depth: float = sample_lod(gbufferD, sampler_linear, float2(uv.x, 1.0 - uv.y), 0.0).r;
	var wpos: float4 = float4(uv * 2.0 - 1.0, depth, 1.0);
	wpos = constants.invVP * wpos;
	return wpos.xyz / wpos.w;
}

fun octahedron_wrap(v: float2): float2 {
	var a: float2;
	if (v.x >= 0.0) {
		a.x = 1.0;
	}
	else {
		a.x = -1.0;
	}
	if (v.y >= 0.0) {
		a.y = 1.0;
	}
	else {
		a.y = -1.0;
	}
	var r: float2;
	r.x = 1.0 - abs(v.y);
	r.y = 1.0 - abs(v.x);
	return r * a;
}

fun get_normal(uv: float2): float3 {
	var g0: float2 = sample_lod(gbuffer0, sampler_linear, float2(uv.x, 1.0 - uv.y), 0.0).rg;
	var n: float3;
	n.z = 1.0 - abs(g0.x) - abs(g0.y);
	if (n.z >= 0.0) {
		n.x = g0.x;
		n.y = g0.y;
	}
	else {
		var fw: float2 = octahedron_wrap(g0.xy);
		n.x = fw.x;
		n.y = fw.y;
	}
	return n;
}

fun cursor_decal_vert(input: vert_in): vert_out {
	var keep: float = input.pos.x + input.nor.x; // hlsl

	var output: vert_out;
	output.tex = input.tex;
	var wpos: float3 = get_pos(constants.mouse);

	var uv1: float2 = constants.mouse + constants.tex_step * float2(4.0, 4.0);
	var uv2: float2 = constants.mouse - constants.tex_step * float2(4.0, 4.0);
	var n: float3 = normalize(get_normal(constants.mouse) + get_normal(uv1) + get_normal(uv2));

	var n_tan: float3;
	var n_bin: float3;
	if (constants.camera_align > 0.0) {
		n_tan = constants.camera_right;
		n_bin = -constants.camera_up;
	}
	else {
		var cam_right: float3 = constants.camera_right;
		if (abs(dot(n, cam_right)) > 0.999) { cam_right = float3(0.0, 0.0, 1.0); }
		n_tan = normalize(cam_right - n * dot(cam_right, n));
		n_bin = cross(n_tan, n);
	}

	// Rotate tangent basis by brush angle
	var r_tan: float3 = constants.angle.x * n_tan + constants.angle.y * n_bin;
	var r_bin: float3 = -constants.angle.y * n_tan + constants.angle.x * n_bin;

	if (vertex_id() == 3) {
		wpos += (-constants.scale_x * r_tan - r_bin) * constants.radius;
	}
	/*else */if (vertex_id() == 2) {
		wpos += ( constants.scale_x * r_tan - r_bin) * constants.radius;
	}
	/*else */if (vertex_id() == 1) {
		wpos += ( constants.scale_x * r_tan + r_bin) * constants.radius;
	}
	/*else */if (vertex_id() == 0) {
		wpos += (-constants.scale_x * r_tan + r_bin) * constants.radius;
	}

	output.pos = constants.VP * float4(wpos, 1.0);
	return output;
}

fun cursor_decal_frag(input: vert_out): float4 {
	var col: float4 = sample_lod(texdecal, sampler_linear, input.tex, 0.0);
	return float4(col.rgb, col.a * constants.opacity);
}

#[pipe]
struct pipe {
	vertex = cursor_decal_vert;
	fragment = cursor_decal_frag;
}