/*
===========================================================================
Copyright (C) 2019 Gian 'myT' Schellenbaum

This file is part of Challenge Quake 3 (CNQ3).

Challenge Quake 3 is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

Challenge Quake 3 is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Challenge Quake 3. If not, see <https://www.gnu.org/licenses/>.
===========================================================================
*/
// linear-space FLOAT to gamma-space UINT8 compute shader

Texture2D<float4>  src : register(t0);
RWTexture2D<uint4> dst : register(u0);

cbuffer Constants : register(b0)
{
	float4 blendColor;
	float intensity;
	float invGamma; // 1.0 / gamma
	float dummy0;
	float dummy1;
}

[numthreads(8, 8, 1)]
void cs_main(uint3 id : SV_DispatchThreadID)
{
	// yes, intensity *should* be done in light-linear space
	// but we keep the old behavior for consistency...
	float4 in0 = src[id.xy];
	float3 in1 = 0.5 * (in0.rgb + blendColor.rgb);
	float3 inV = lerp(in0.rgb, in1.rgb, blendColor.a);
	float3 out0 = pow(max(inV, 0.0), invGamma);
	float3 out1 = out0 * intensity;
	float4 outV = saturate(float4(out1, in0.a));
	dst[id.xy] = outV * 255.0;
}