Duckstation/data/resources/shaders/reshade/Shaders/crt-royale/lib/quad-pixel-communication.fxh

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#ifndef _QUAD_PIXEL_COMMUNICATION_H
#define _QUAD_PIXEL_COMMUNICATION_H
///////////////////////////////// MIT LICENSE ////////////////////////////////
// Copyright (C) 2014 TroggleMonkey*
//
// 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.
///////////////////////////////// DISCLAIMER /////////////////////////////////
// *This code was inspired by "Shader Amortization using Pixel Quad Message
// Passing" by Eric Penner, published in GPU Pro 2, Chapter VI.2. My intent
// is not to plagiarize his fundamentally similar code and assert my own
// copyright, but the algorithmic helper functions require so little code that
// implementations can't vary by much except bugfixes and conventions. I just
// wanted to license my own particular code here to avoid ambiguity and make it
// clear that as far as I'm concerned, people can do as they please with it.
///////////////////////////////// DESCRIPTION ////////////////////////////////
// Given screen pixel numbers, derive a "quad vector" describing a fragment's
// position in its 2x2 pixel quad. Given that vector, obtain the values of any
// variable at neighboring fragments.
// Requires: Using this file in general requires:
// 1.) ddx() and ddy() are present in the current Cg profile.
// 2.) The GPU driver is using fine/high-quality derivatives.
// Functions will give incorrect results if this is not true,
// so a test function is included.
///////////////////// QUAD-PIXEL COMMUNICATION PRIMITIVES ////////////////////
float4 get_quad_vector_naive(float4 output_pixel_num_wrt_uvxy)
{
// Requires: Two measures of the current fragment's output pixel number
// in the range ([0, output_size.x), [0, output_size.y)):
// 1.) output_pixel_num_wrt_uvxy.xy increase with uv coords.
// 2.) output_pixel_num_wrt_uvxy.zw increase with screen xy.
// Returns: Two measures of the fragment's position in its 2x2 quad:
// 1.) The .xy components are its 2x2 placement with respect to
// uv direction (the origin (0, 0) is at the top-left):
// top-left = (-1.0, -1.0) top-right = ( 1.0, -1.0)
// bottom-left = (-1.0, 1.0) bottom-right = ( 1.0, 1.0)
// You need this to arrange/weight shared texture samples.
// 2.) The .zw components are its 2x2 placement with respect to
// screen xy direction (position); the origin varies.
// quad_gather needs this measure to work correctly.
// Note: quad_vector.zw = quad_vector.xy * float2(
// ddx(output_pixel_num_wrt_uvxy.x),
// ddy(output_pixel_num_wrt_uvxy.y));
// Caveats: This function assumes the GPU driver always starts 2x2 pixel
// quads at even pixel numbers. This assumption can be wrong
// for odd output resolutions (nondeterministically so).
float4 pixel_odd = frac(output_pixel_num_wrt_uvxy * 0.5) * 2.0;
float4 quad_vector = pixel_odd * 2.0 - float4(1.0, 1.0, 1.0, 1.0);
return quad_vector;
}
float4 get_quad_vector(float4 output_pixel_num_wrt_uvxy)
{
// Requires: Same as get_quad_vector_naive() (see that first).
// Returns: Same as get_quad_vector_naive() (see that first), but it's
// correct even if the 2x2 pixel quad starts at an odd pixel,
// which can occur at odd resolutions.
float4 quad_vector_guess =
get_quad_vector_naive(output_pixel_num_wrt_uvxy);
// If quad_vector_guess.zw doesn't increase with screen xy, we know
// the 2x2 pixel quad starts at an odd pixel:
float2 odd_start_mirror = 0.5 * float2(ddx(quad_vector_guess.z),
ddy(quad_vector_guess.w));
return quad_vector_guess * odd_start_mirror.xyxy;
}
float4 get_quad_vector(float2 output_pixel_num_wrt_uv)
{
// Requires: 1.) ddx() and ddy() are present in the current Cg profile.
// 2.) output_pixel_num_wrt_uv must increase with uv coords and
// measure the current fragment's output pixel number in:
// ([0, output_size.x), [0, output_size.y))
// Returns: Same as get_quad_vector_naive() (see that first), but it's
// correct even if the 2x2 pixel quad starts at an odd pixel,
// which can occur at odd resolutions.
// Caveats: This function requires less information than the version
// taking a float4, but it's potentially slower.
// Do screen coords increase with or against uv? Get the direction
// with respect to (uv.x, uv.y) for (screen.x, screen.y) in {-1, 1}.
float2 screen_uv_mirror = float2(ddx(output_pixel_num_wrt_uv.x),
ddy(output_pixel_num_wrt_uv.y));
float2 pixel_odd_wrt_uv = frac(output_pixel_num_wrt_uv * 0.5) * 2.0;
float2 quad_vector_uv_guess = (pixel_odd_wrt_uv - float2(0.5, 0.5)) * 2.0;
float2 quad_vector_screen_guess = quad_vector_uv_guess * screen_uv_mirror;
// If quad_vector_screen_guess doesn't increase with screen xy, we know
// the 2x2 pixel quad starts at an odd pixel:
float2 odd_start_mirror = 0.5 * float2(ddx(quad_vector_screen_guess.x),
ddy(quad_vector_screen_guess.y));
float4 quad_vector_guess = float4(
quad_vector_uv_guess, quad_vector_screen_guess);
return quad_vector_guess * odd_start_mirror.xyxy;
}
void quad_gather(float4 quad_vector, float4 curr,
out float4 adjx, out float4 adjy, out float4 diag)
{
// Requires: 1.) ddx() and ddy() are present in the current Cg profile.
// 2.) The GPU driver is using fine/high-quality derivatives.
// 3.) quad_vector describes the current fragment's location in
// its 2x2 pixel quad using get_quad_vector()'s conventions.
// 4.) curr is any vector you wish to get neighboring values of.
// Returns: Values of an input vector (curr) at neighboring fragments
// adjacent x, adjacent y, and diagonal (via out parameters).
adjx = curr - ddx(curr) * quad_vector.z;
adjy = curr - ddy(curr) * quad_vector.w;
diag = adjx - ddy(adjx) * quad_vector.w;
}
void quad_gather(float4 quad_vector, float3 curr,
out float3 adjx, out float3 adjy, out float3 diag)
{
// Float3 version
adjx = curr - ddx(curr) * quad_vector.z;
adjy = curr - ddy(curr) * quad_vector.w;
diag = adjx - ddy(adjx) * quad_vector.w;
}
void quad_gather(float4 quad_vector, float2 curr,
out float2 adjx, out float2 adjy, out float2 diag)
{
// Float2 version
adjx = curr - ddx(curr) * quad_vector.z;
adjy = curr - ddy(curr) * quad_vector.w;
diag = adjx - ddy(adjx) * quad_vector.w;
}
float4 quad_gather(float4 quad_vector, float curr)
{
// Float version:
// Returns: return.x == current
// return.y == adjacent x
// return.z == adjacent y
// return.w == diagonal
float4 all = float4(curr, curr, curr, curr);
all.y = all.x - ddx(all.x) * quad_vector.z;
all.zw = all.xy - ddy(all.xy) * quad_vector.w;
return all;
}
float4 quad_gather_sum(float4 quad_vector, float4 curr)
{
// Requires: Same as quad_gather()
// Returns: Sum of an input vector (curr) at all fragments in a quad.
float4 adjx, adjy, diag;
quad_gather(quad_vector, curr, adjx, adjy, diag);
return (curr + adjx + adjy + diag);
}
float3 quad_gather_sum(float4 quad_vector, float3 curr)
{
// Float3 version:
float3 adjx, adjy, diag;
quad_gather(quad_vector, curr, adjx, adjy, diag);
return (curr + adjx + adjy + diag);
}
float2 quad_gather_sum(float4 quad_vector, float2 curr)
{
// Float2 version:
float2 adjx, adjy, diag;
quad_gather(quad_vector, curr, adjx, adjy, diag);
return (curr + adjx + adjy + diag);
}
float quad_gather_sum(float4 quad_vector, float curr)
{
// Float version:
float4 all_values = quad_gather(quad_vector, curr);
return (all_values.x + all_values.y + all_values.z + all_values.w);
}
bool fine_derivatives_working(float4 quad_vector, float4 curr)
{
// Requires: 1.) ddx() and ddy() are present in the current Cg profile.
// 2.) quad_vector describes the current fragment's location in
// its 2x2 pixel quad using get_quad_vector()'s conventions.
// 3.) curr must be a test vector with non-constant derivatives
// (its value should change nonlinearly across fragments).
// Returns: true if fine/hybrid/high-quality derivatives are used, or
// false if coarse derivatives are used or inconclusive
// Usage: Test whether quad-pixel communication is working!
// Method: We can confirm fine derivatives are used if the following
// holds (ever, for any value at any fragment):
// (ddy(curr) != ddy(adjx)) or (ddx(curr) != ddx(adjy))
// The more values we test (e.g. test a float4 two ways), the
// easier it is to demonstrate fine derivatives are working.
// TODO: Check for floating point exact comparison issues!
float4 ddx_curr = ddx(curr);
float4 ddy_curr = ddy(curr);
float4 adjx = curr - ddx_curr * quad_vector.z;
float4 adjy = curr - ddy_curr * quad_vector.w;
bool ddy_different = any(bool4(ddy_curr.x != ddy(adjx).x, ddy_curr.y != ddy(adjx).y, ddy_curr.z != ddy(adjx).z, ddy_curr.w != ddy(adjx).w));
bool ddx_different = any(bool4(ddx_curr.x != ddx(adjy).x, ddx_curr.y != ddx(adjy).y, ddx_curr.z != ddx(adjy).z, ddx_curr.w != ddx(adjy).w));
return any(bool2(ddy_different, ddx_different));
}
bool fine_derivatives_working_fast(float4 quad_vector, float curr)
{
// Requires: Same as fine_derivatives_working()
// Returns: Same as fine_derivatives_working()
// Usage: This is faster than fine_derivatives_working() but more
// likely to return false negatives, so it's less useful for
// offline testing/debugging. It's also useless as the basis
// for dynamic runtime branching as of May 2014: Derivatives
// (and quad-pixel communication) are currently disallowed in
// branches. However, future GPU's may allow you to use them
// in dynamic branches if you promise the branch condition
// evaluates the same for every fragment in the quad (and/or if
// the driver enforces that promise by making a single fragment
// control branch decisions). If that ever happens, this
// version may become a more economical choice.
float ddx_curr = ddx(curr);
float ddy_curr = ddy(curr);
float adjx = curr - ddx_curr * quad_vector.z;
return (ddy_curr != ddy(adjx));
}
#endif // _QUAD_PIXEL_COMMUNICATION_H