Stephen Hill selfshadow

A quick breakdown of lighting in the restir-meets-surfel branch of my renderer, where I revive some olde surfel experiments, and generously sprinkle ReSTIR on top.

General remarks

Please note that this is all based on work-in-progress experimental software, and represents a single snapshot in development history. Things will certainly change 😛

Due to how I'm capturing this, there's frame-to-frame variability, e.g. different rays being shot, TAA shimmering slightly. Some of the images come from a dedicated visualization pass, and are anti-aliased, and some show internal buffers which are not anti-aliased.

Final images

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Please refer to this blogpost to get an overview.

Replace *-INSTANCE with one of the public instances listed in the scrapers section. Replace CAPITALIZED words with their corresponding identifiers on the website.

	// Copyright (c) 2023 Tomasz Stachowiak
	//
	// This contribution is dual licensed under EITHER OF
	//
	// Apache License, Version 2.0, (http://www.apache.org/licenses/LICENSE-2.0)
	// MIT license (http://opensource.org/licenses/MIT)
	//
	// at your option.

	#include "/inc/frame_constants.hlsl"

	( User Mathematica initialization file )

	( See https://reference.wolfram.com/language/tutorial/ConfigurationFiles.html for info on instaling this file )

	( Display graphics inline in iTerm2. I don't know an easy way to test if we're running in iTerm2 without looking at the process table. )

	imgcat[image_Graphics]:=(
	WriteString[$Output, "\033]1337;File=inline=1:"<>ExportString[ExportString[image,"PNG"],"Base64"]<>"\007"];
	Null
	)

	#pragma section(".remotery_code", read, execute)

	__declspec(allocate(".remotery_code"))
	static const uint8_t code[] =
	{
	0x50, // push rax
	0x9C, // pushfq
	0x53, // push rbx
	0x51, // push rcx
	0x52, // push rdx

	Shader "WorldNormalFromDepthTexture"
	{
	Properties {
	[KeywordEnum(3 Tap, 4 Tap, Improved, Accurate)] _ReconstructionMethod ("Normal Reconstruction Method", Float) = 0
	}

	SubShader
	{
	Tags { "RenderType"="Transparent" "Queue"="Transparent" }
	LOD 100

	// Projects the specified position (point) onto the plane with the specified origin and normal.
	float3 projectOnPlane(float3 position, float3 origin, float3 normal)
	{
	return position - dot(position - origin, normal) * normal;
	}

	// Computes the shading position of the specified geometric position and vertex positions and
	// normals. For a triangle with normals describing a convex surface, this point will be slightly
	// above the surface. For a concave surface, the geometry position is used directly.
	// NOTE: The difference between the shading position and geometry position is significant when

Stephen Hill selfshadow

General remarks

Final images

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	In shader programming, you often run into a problem where you want to iterate an array in memory over all pixels in a compute shader
	group (tile). Tiled deferred lighting is the most common case. 8x8 tile loops over a light list culled for that tile.

	Simplified HLSL code looks like this:

	Buffer<float4> lightDatas;
	Texture2D<uint2> lightStartCounts;
	RWTexture2D<float4> output;

	[numthreads(8, 8, 1)]

	#include <emmintrin.h>
	#include <tmmintrin.h> // for PSHUFB; this isn't strictly necessary (see comments in reverse_s16)

	typedef int16_t S16;
	typedef __m128i Vec;

	static inline Vec load8_s16(const S16 x) { return _mm_loadu_si128((const __m128i ) x); }
	static inline void store8_s16(S16 x, Vec v) { _mm_storeu_si128((__m128i ) x, v); }

	static inline void sort_two(Vec &a, Vec &b) { Vec t = a; a = _mm_min_epi16(a, b); b = _mm_max_epi16(b, t); }

	#include <stdio.h>

	// #define CLANG_EXTENSION
	// Clang compile with -O3

	#define VS_EXTENSION
	// https://godbolt.org/z/sVWrF4
	// Clang compile with -O3 -fms-compatibility
	// VS2017 compile with /O3