/*
===========================================================================
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/>.
===========================================================================
*/
// 8-tap 1D filter compute shader

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

cbuffer Constants : register(b0)
{
	float4 weights;
	int2 maxSize;
	int2 scale;
	int2 offset;
	uint clampMode; // 0 = repeat
	uint dummy;
}

uint2 FixCoords(int2 c)
{
	if(clampMode > 0)
	{
		// clamp
		return uint2(clamp(c, int2(0, 0), maxSize));
	}

	// repeat
	return uint2(c & maxSize);
}

[numthreads(8, 8, 1)]
void cs_main(uint3 id : SV_DispatchThreadID)
{
	int2 base = int2(id.xy) * scale;
	float4 r = float4(0, 0, 0, 0);
	r += src[FixCoords(base - offset * 3)] * weights.x;
	r += src[FixCoords(base - offset * 2)] * weights.y;
	r += src[FixCoords(base - offset * 1)] * weights.z;
	r += src[          base              ] * weights.w;
	r += src[          base + offset     ] * weights.w;
	r += src[FixCoords(base + offset * 2)] * weights.z;
	r += src[FixCoords(base + offset * 3)] * weights.y;
	r += src[FixCoords(base + offset * 4)] * weights.x;
	dst[id.xy] = r;
}