├── .gitattributes
├── ConeSphereOcclusionLUT.exe
├── ConeSphereOcclusionLUT.sln
├── ConeSphereOcclusionLUT.vcxproj
├── README.md
├── cone_sphere_occlusion_lut.tga
└── main.cpp


/.gitattributes:
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12 | *.dot  diff=astextplain
13 | *.DOT  diff=astextplain
14 | *.pdf  diff=astextplain
15 | *.PDF	 diff=astextplain
16 | *.rtf	 diff=astextplain
17 | *.RTF	 diff=astextplain
18 | 


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/ConeSphereOcclusionLUT.exe:
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https://raw.githubusercontent.com/knarkowicz/ConeSphereOcclusionLUT/cc329868d7b4fb689f5c4a0c9e917351f6d06757/ConeSphereOcclusionLUT.exe


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/ConeSphereOcclusionLUT.sln:
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/ConeSphereOcclusionLUT.vcxproj:
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/README.md:
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1 | ConeSphereOcclusionLUT
2 | =======
3 | 
4 | ConeSphereOcclusionLUT generates a cone sphere occlusion LUT to be used with TLoU style capsule AO shadows. For details see page 26 of ["Lighting Technology Of "The Last Of Us""](http://miciwan.com/SIGGRAPH2013/Lighting%20Technology%20of%20The%20Last%20Of%20Us.pdf) talk by Michał Iwanicki . This slick technique was originally created for SPU, but it perfectly works with compute shaders.
5 | 


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/cone_sphere_occlusion_lut.tga:
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https://raw.githubusercontent.com/knarkowicz/ConeSphereOcclusionLUT/cc329868d7b4fb689f5c4a0c9e917351f6d06757/cone_sphere_occlusion_lut.tga


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/main.cpp:
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  1 | #include <math.h>
  2 | #include <stdint.h>
  3 | #include <stdio.h>
  4 | #include <string.h>
  5 | #include <stdlib.h>
  6 | 
  7 | float const MATH_PI			= 3.14159265359f;
  8 | unsigned const SAMPLE_NUM	= 10000;
  9 | 
 10 | struct Vec3
 11 | {
 12 | 	float x;
 13 | 	float y;
 14 | 	float z;
 15 | };
 16 | 
 17 | float dot( Vec3 a, Vec3 b )
 18 | {
 19 | 	return a.x * b.x + a.y * b.y + a.z * b.z;
 20 | }
 21 | 
 22 | void SaveTGA( char const* path, unsigned width, unsigned height, void const* data )
 23 | {
 24 | 	#pragma pack( push, 1 )
 25 | 	struct STGAHeader 
 26 | 	{
 27 | 	   char  idlength;
 28 | 	   char  colourmaptype;
 29 | 	   char  datatypecode;
 30 | 	   short int colourmaporigin;
 31 | 	   short int colourmaplength;
 32 | 	   char  colourmapdepth;
 33 | 	   short int x_origin;
 34 | 	   short int y_origin;
 35 | 	   short width;
 36 | 	   short height;
 37 | 	   char  bitsperpixel;
 38 | 	   char  imagedescriptor;
 39 | 	};
 40 | 	#pragma pack( pop )
 41 | 
 42 | 
 43 | 	FILE* f = nullptr;
 44 |     fopen_s( &f, path, "wb" );
 45 |     if ( !f )
 46 |     {
 47 |         return;
 48 |     }
 49 | 
 50 | 	STGAHeader header;
 51 | 	memset( &header, 0, sizeof( header ) );
 52 | 	header.width			= width;
 53 | 	header.height			= height;
 54 | 	header.datatypecode		= 2;
 55 | 	header.bitsperpixel		= 24;
 56 | 	header.imagedescriptor	= 1 << 5;
 57 | 	fwrite( &header, sizeof( header ), 1, f );
 58 | 
 59 | 	fwrite( data, width * height * 3, 1, f );
 60 | 
 61 | 	fclose( f );
 62 | }
 63 | 
 64 | Vec3 RandomConeRays[ SAMPLE_NUM ];
 65 | 
 66 | void GenerateRandomConeRays( float coneAngle )
 67 | {
 68 | 	float const cosConeAngle = cosf( 0.5f * ( coneAngle * MATH_PI / 180.0f ) );
 69 | 	for ( unsigned iSample = 0; iSample < SAMPLE_NUM; ++iSample )
 70 | 	{
 71 | 		float cosTheta	= ( (float) rand() / RAND_MAX ) * ( 1.0f - cosConeAngle ) + cosConeAngle;
 72 | 		float sinTheta	= sqrtf( 1.0f - cosTheta * cosTheta );
 73 | 		float phi		= MATH_PI * ( (float) rand() / RAND_MAX ) * 2.0f - 1.0f;
 74 | 		float cosPhi	= cosf( phi );
 75 | 		float sinPhi	= sinf( phi );
 76 | 
 77 | 		RandomConeRays[ iSample ] = { sinTheta * cosPhi, sinTheta * sinPhi, cosTheta };
 78 | 	}
 79 | }
 80 | 
 81 | float Occlusion( float occluderAngleSin, float occluderToBeamAngleCos )
 82 | {	
 83 | 	float const occluderToBeamAngleSin	= sqrtf( 1.0f - occluderToBeamAngleCos * occluderToBeamAngleCos );
 84 | 	float const occluderAngleCos		= sqrtf( 1.0f - occluderAngleSin * occluderAngleSin );
 85 | 	Vec3 const occluderDir				= { occluderToBeamAngleSin, 0.0f, occluderToBeamAngleCos };
 86 | 
 87 | 	unsigned hitNum = 0;
 88 | 	for ( unsigned iSample = 0; iSample < SAMPLE_NUM; ++iSample )
 89 | 	{
 90 | 		if ( dot( occluderDir, RandomConeRays[ iSample ] ) > occluderAngleCos )
 91 | 		{
 92 | 			++hitNum;
 93 | 		}
 94 | 	}
 95 | 
 96 | 	return 1.0f - hitNum / (float) SAMPLE_NUM;
 97 | }
 98 | 
 99 | int main( int argc, char** argv )
100 | {
101 |     if ( argc < 4 )
102 |     {
103 |         printf( "Incorrect params\n" );
104 |         printf( "Usage: ConeSphereOcclusionLUT.exe lut_width lut_height cone_angle_in_degress\n" );
105 |         printf( "ConeSphereOcclusionLUT.exe 128 64 30\n" );
106 |         return 1;
107 |     }
108 | 
109 | 	float coneAngle		= 30.0f;
110 | 	unsigned lutWidth	= 128;
111 | 	unsigned lutHeight	= 64;
112 | 	sscanf_s( argv[ 1 ], "%u", &lutWidth );
113 | 	sscanf_s( argv[ 2 ], "%u", &lutHeight );
114 | 	sscanf_s( argv[ 3 ], "%f", &coneAngle );
115 | 
116 | 	uint8_t* lutData = new uint8_t[ lutWidth * lutHeight * 3 ];
117 | 	GenerateRandomConeRays( coneAngle );
118 | 
119 | 	for ( unsigned iSinTheta = 0; iSinTheta < lutHeight; ++iSinTheta ) // angle subtended by the occluder [0;1]
120 | 	{
121 | 		float const sinTheta = iSinTheta / ( lutHeight - 1.0f );
122 | 
123 | 		for ( unsigned iCosPhi = 0; iCosPhi < lutWidth; ++iCosPhi ) // angle between the cone axis and the vector pointing towards the occluder (sphere) center [-1;1]
124 | 		{
125 | 			float const cosPhi = 2.0f * ( iCosPhi / ( lutWidth - 1.0f ) ) - 1.0f;
126 | 			float const sampleValue = Occlusion( sinTheta, cosPhi );
127 | 
128 | 			uint8_t sampleU8 = uint8_t( sampleValue * 255.0f + 0.5f );
129 | 			lutData[ iCosPhi * 3 + iSinTheta * lutWidth * 3 + 0 ] = sampleU8;
130 | 			lutData[ iCosPhi * 3 + iSinTheta * lutWidth * 3 + 1 ] = sampleU8;
131 | 			lutData[ iCosPhi * 3 + iSinTheta * lutWidth * 3 + 2 ] = sampleU8;
132 | 		}
133 | 	}
134 | 
135 | 	SaveTGA( "cone_sphere_occlusion_lut.tga", lutWidth, lutHeight, lutData );
136 | 	delete[] lutData;
137 | 
138 | 	return 0;
139 | }


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