armorpaint/paint/shaders/deferred_light.kong

#[set(everything)]
const constants: {
	invVP: float4x4;
	eye: float3;
	envmap_data: float4; // angle, sin(angle), cos(angle), strength
	envmap_num_mipmaps: int;
	camera_proj: float2;
	eye_look: float3;
	shirr0: float4;
	shirr1: float4;
	shirr2: float4;
	shirr3: float4;
	shirr4: float4;
	shirr5: float4;
	shirr6: float4;
};

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

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

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

#[set(everything)]
const gbuffer1: tex2d;

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

#[set(everything)]
const senvmap_radiance0: tex2d;

#[set(everything)]
const senvmap_radiance1: tex2d;

#[set(everything)]
const senvmap_radiance2: tex2d;

#[set(everything)]
const senvmap_radiance3: tex2d;

#[set(everything)]
const senvmap_radiance4: tex2d;

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

const PI: float = 3.14159265358979;
const PI2: float = 6.28318530718;

struct vert_in {
	pos: float2;
}

struct vert_out {
	pos: float4;
	tex: float2;
	view_ray: float3;
}

fun deferred_light_vert(input: vert_in): vert_out {
	var output: vert_out;
	output.tex = input.pos.xy * 0.5 + 0.5;
	output.tex.y = 1.0 - output.tex.y;
	output.pos = float4(input.pos.xy, 0.0, 1.0);

	// NDC (at the back of cube)
	var v: float4 = float4(input.pos.xy, 1.0, 1.0);
	v = constants.invVP * v;
	v.xyz = v.xyz / v.w;
	output.view_ray = v.xyz - constants.eye;

	return output;
}

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 = abs(v.y);
	r.y = abs(v.x);
	r.x = 1.0 - r.x;
	r.y = 1.0 - r.y;
	return r * a;

	// return (1.0 - abs(v.yx)) * (float2(v.x >= 0.0 ? 1.0 : -1.0, v.y >= 0.0 ? 1.0 : -1.0));
}

// fun unpack_f32_i16(val: float, out f: float, out i: uint) {
// 	// Constant optimize by compiler
// 	const num_bit_target: int = 16;
// 	const num_bit_i: int = 4;
// 	const prec: float = float(1 << num_bit_target);
// 	const maxi: float = float(1 << num_bit_i);
// 	const prec_minus_one: float = prec - 1.0;
// 	const t1: float = ((prec / maxi) - 1.0) / prec_minus_one;
// 	const t2: float = (prec / maxi) / prec_minus_one;
// 	// Code
// 	// extract integer part
// 	// + rcp(prec_minus_one) to deal with precision issue
// 	i = uint((val / t2) + (1.0 / prec_minus_one));
// 	// Now that we have i, solve formula in pack_f32_i16 for f
// 	//f = (val - t2 * float(i)) / t1 => convert in mads form
// 	f = clamp((-t2 * float(i) + val) / t1, 0.0, 1.0); // Saturate in case of precision issue
// }

fun surface_albedo(base_color: float3, metalness: float): float3 {
	return lerp3(base_color, float3(0.0, 0.0, 0.0), metalness);
}

fun surface_f0(base_color: float3, metalness: float): float3 {
	return lerp3(float3(0.04, 0.04, 0.04), base_color, metalness);
}

fun get_pos(eye: float3, eye_look: float3, view_ray: float3, depth: float, camera_proj: float2): float3 {
	// eye_look, view_ray should be normalized
	var linear_depth: float = camera_proj.y / (depth - camera_proj.x);
	var view_z_dist: float = dot(eye_look, view_ray);
	var wposition: float3 = eye + view_ray * (linear_depth / view_z_dist);
	return wposition;
}

const c1: float = 0.429043;
const c2: float = 0.511664;
const c3: float = 0.743125;
const c4: float = 0.886227;
const c5: float = 0.247708;

fun sh_irradiance(nor: float3): float3 {
	// TODO: Use padding for 4th component and pass shirr[].xyz directly
	var cl00: float3 = float3(constants.shirr0.x, constants.shirr0.y, constants.shirr0.z);
	var cl1m1: float3 = float3(constants.shirr0.w, constants.shirr1.x, constants.shirr1.y);
	var cl10: float3 = float3(constants.shirr1.z, constants.shirr1.w, constants.shirr2.x);
	var cl11: float3 = float3(constants.shirr2.y, constants.shirr2.z, constants.shirr2.w);
	var cl2m2: float3 = float3(constants.shirr3.x, constants.shirr3.y, constants.shirr3.z);
	var cl2m1: float3 = float3(constants.shirr3.w, constants.shirr4.x, constants.shirr4.y);
	var cl20: float3 = float3(constants.shirr4.z, constants.shirr4.w, constants.shirr5.x);
	var cl21: float3 = float3(constants.shirr5.y, constants.shirr5.z, constants.shirr5.w);
	var cl22: float3 = float3(constants.shirr6.x, constants.shirr6.y, constants.shirr6.z);
	return (
		cl22 * c1 * (nor.y * nor.y - (-nor.z) * (-nor.z)) +
		cl20 * c3 * nor.x * nor.x +
		cl00 * c4 -
		cl20 * c5 +
		cl2m2 * 2.0 * c1 * nor.y * (-nor.z) +
		cl21  * 2.0 * c1 * nor.y * nor.x +
		cl2m1 * 2.0 * c1 * (-nor.z) * nor.x +
		cl11  * 2.0 * c2 * nor.y +
		cl1m1 * 2.0 * c2 * (-nor.z) +
		cl10  * 2.0 * c2 * nor.x
	);
}

fun mip_from_roughness(roughness: float, num_mipmaps: float): float {
	// First mipmap level = roughness 0, last = roughness = 1
	return roughness * num_mipmaps;
}

fun envmap_equirect(normal: float3, angle: float): float2 {
	var phi: float = acos(normal.z);
	var theta: float = atan2(-normal.y, normal.x) + PI + angle;
	return float2(theta / PI2, phi / PI);
}

fun envmap_sample(lod: float, coord: float2): float3 {
	if (lod == 0.0) {
		return sample_lod(senvmap_radiance, sampler_linear, coord, 0.0).rgb;
	}
	if (lod == 1.0) {
		return sample_lod(senvmap_radiance0, sampler_linear, coord, 0.0).rgb;
	}
	if (lod == 2.0) {
		return sample_lod(senvmap_radiance1, sampler_linear, coord, 0.0).rgb;
	}
	if (lod == 3.0) {
		return sample_lod(senvmap_radiance2, sampler_linear, coord, 0.0).rgb;
	}
	if (lod == 4.0) {
		return sample_lod(senvmap_radiance3, sampler_linear, coord, 0.0).rgb;
	}
	return sample_lod(senvmap_radiance4, sampler_linear, coord, 0.0).rgb;
}

// https://www.unrealengine.com/en-US/blog/physically-based-shading-on-mobile
fun env_brdf_approx(specular: float3, roughness: float, dotnv: float): float3 {
	var c0: float4 = float4(-1.0, -0.0275, -0.572, 0.022);
	var c1: float4 = float4(1.0, 0.0425, 1.04, -0.04);
	var r: float4 = c0 * roughness + c1;
	var a004: float = min(r.x * r.x, exp((-9.28 * dotnv) * log(2.0))) * r.x + r.y;
	var ab: float2 = float2(-1.04, 1.04) * a004 + r.zw;
	return specular * ab.x + ab.y;
}

fun deferred_light_frag(input: vert_out): float4 {
	// normal.xy, roughness, metallic/matid
	var g0: float4 = sample_lod(gbuffer0, sampler_linear, input.tex, 0.0);

	var n: float3;
	n.z = 1.0 - abs(g0.x) - abs(g0.y);
	if (n.z >= 0.0) {
		//n.xy = g0.xy;
		n.x = g0.x;
		n.y = g0.y;
	}
	else {
		//n.xy = octahedron_wrap(g0.xy);
		var f2: float2 = octahedron_wrap(g0.xy);
		n.x = f2.x;
		n.y = f2.y;
	}
	n = normalize(n);

	var roughness: float = g0.b;
	var metallic: float;
	var matid: uint;
	// unpack_f32_i16(g0.a, metallic, matid);
	matid = uint((g0.a / 0.06250047610269868710814625956118106842041015625) + (1.0 / 65535.0));
	metallic = clamp((-0.06250047610269868710814625956118106842041015625 * float(matid) + g0.a) / 0.062485207147583624058737396240234375, 0.0, 1.0);

	var g1: float4 = sample_lod(gbuffer1, sampler_linear, input.tex, 0.0); // basecolor.rgb, occ
	var occ: float = g1.a;
	var albedo: float3 = surface_albedo(g1.rgb, metallic);
	var f0: float3 = surface_f0(g1.rgb, metallic);

	var depth: float = sample_lod(gbufferD, sampler_linear, input.tex, 0.0).r;
	var p: float3 = get_pos(constants.eye, constants.eye_look, normalize(input.view_ray), depth, constants.camera_proj);
	var v: float3 = normalize(constants.eye - p);
	var dotnv: float = max(0.0, dot(n, v));
	occ = lerp(1.0, occ, dotnv); // ao fresnel

	// Envmap
	var envl: float3 = sh_irradiance(
		float3(
			n.x * constants.envmap_data.z - n.y * constants.envmap_data.y,
			n.x * constants.envmap_data.y + n.y * constants.envmap_data.z,
			n.z
		)
	);
	// envl /= PI;
	envl = envl / PI;

	var reflection_world: float3 = reflect(-v, n);
	// var lod: float = mip_from_roughness(roughness, float(constants.envmap_num_mipmaps));
	// var prefiltered_color: float3 = sample_lod(senvmap_radiance, sampler_linear, envmap_equirect(reflection_world, constants.envmap_data.x), lod).rgb;
	var lod: float = mip_from_roughness(roughness, 5.0);
	var lod0: float = floor(lod);
	var lod1: float = ceil(lod);
	var lodf: float = lod - lod0;
	var envmap_coord: float2 = envmap_equirect(reflection_world, constants.envmap_data.x);
	var lodc0: float3 = envmap_sample(lod0, envmap_coord);
	var lodc1: float3 = envmap_sample(lod1, envmap_coord);
	var prefiltered_color: float3 = lerp3(lodc0, lodc1, lodf);

	envl.rgb = envl.rgb * albedo;
	// Indirect specular
	// var env_brdf: float4 = senvmap_brdf[uint2(uint(dotnv * 255.0), uint(roughness * 255.0))];
	// envl.rgb += prefiltered_color * (f0 * env_brdf.x + env_brdf.y);
	// envl.rgb = envl.rgb + (prefiltered_color * (f0 * env_brdf.x + env_brdf.y));
	envl.rgb = envl.rgb + prefiltered_color * env_brdf_approx(f0, roughness, dotnv) * 0.5;

	envl.rgb = envl.rgb * constants.envmap_data.w * occ;

	var color: float4;
	color.rgb = envl.rgb;
	color.rgb = color.rgb * sample_lod(ssaotex, sampler_linear, input.tex, 0.0).r;

	// if (matid == uint(1)) { // Emission
	if (matid == uint(1.0)) { // Emission
		color.rgb = color.rgb + g1.rgb; // materialid
		//albedo = float3(0.0, 0.0, 0.0);
	}

	color.rgb = max3(color.rgb, float3(0.0, 0.0, 0.0));
	color.a = 1.0; // Mark as opaque
	return color;
}

#[pipe]
struct pipe {
	vertex = deferred_light_vert;
	fragment = deferred_light_frag;
}