// Copyright (C) 2009-present, Panagiotis Christopoulos Charitos and contributors.
// All rights reserved.
// Code licensed under the BSD License.
// http://www.anki3d.org/LICENSE

#pragma anki technique vert pixel

#include <AnKi/Shaders/QuadVert.hlsl>

#if ANKI_PIXEL_SHADER
#	include <AnKi/Shaders/Functions.hlsl>

SamplerState g_nearestAnyClampSampler : register(s0);
SamplerState g_linearAnyClampSampler : register(s1);
Texture2D g_depthRt : register(t0);
Texture3D<Vec4> g_fogVolume : register(t1);

struct Constants
{
	F32 m_zSplitCount;
	F32 m_finalZSplit;
	F32 m_near;
	F32 m_far;
};
ANKI_FAST_CONSTANTS(Constants, g_consts)

Vec4 main(VertOut input) : SV_TARGET0
{
	const Vec2 uv = input.m_uv;
	Vec3 uvw;

	// Compute W coordinate
	const F32 depth = g_depthRt.SampleLevel(g_nearestAnyClampSampler, uv, 0.0).r;
	const F32 linearDepth = linearizeDepth(depth, g_consts.m_near, g_consts.m_far);
	uvw.z = linearDepth * (g_consts.m_zSplitCount / (g_consts.m_finalZSplit + 1.0f));

	// Compute UV coordinates
	uvw.xy = uv;

	// Read the volume
	const Vec4 fogVals = g_fogVolume.SampleLevel(g_linearAnyClampSampler, uvw, 0.0);
	const Vec3 inScattering = fogVals.rgb;
	const F32 transmittance = fogVals.a;

	// Apply the fog
	return Vec4(inScattering, transmittance);
}
#endif // ANKI_PIXEL_SHADER