rgtc.comp

#version 450
/* Copyright (c) 2020-2022 Hans-Kristian Arntzen
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#extension GL_EXT_samplerless_texture_functions : require
layout(local_size_x = 4, local_size_y = 4, local_size_z = 4) in;

#include "rgtc.h"

layout(set = 0, binding = 0) writeonly uniform image2D uOutput;
layout(set = 0, binding = 1) uniform utexture2D uInput;

layout(push_constant) uniform Registers
{
    ivec2 resolution;
} registers;

layout(constant_id = 0) const bool DUAL_COMPONENT = false;

ivec2 build_coord()
{
    ivec2 base = ivec2(gl_WorkGroupID.xy) * 8;
    base.x += 4 * (int(gl_LocalInvocationID.z) & 1);
    base.y += 2 * (int(gl_LocalInvocationID.z) & 2);
    base += ivec2(gl_LocalInvocationID.xy);
    return base;
}

void main()
{
    ivec2 coord = build_coord();
    if (any(greaterThanEqual(coord, registers.resolution)))
        return;

    ivec2 tile_coord = coord >> 2;
    ivec2 pixel_coord = coord & 3;
    int linear_pixel = 4 * pixel_coord.y + pixel_coord.x;
    uvec4 payload = texelFetch(uInput, tile_coord, 0);

    vec4 rg = vec4(0);
    rg.x = decode_alpha_rgtc(payload.xy, linear_pixel);
    if (DUAL_COMPONENT)
        rg.y = decode_alpha_rgtc(payload.zw, linear_pixel);

    imageStore(uOutput, coord, rg);
}