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Shader "Hidden/Universal Render Pipeline/PaniniProjection"
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{
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HLSLINCLUDE
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#pragma exclude_renderers gles
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#pragma multi_compile_local _GENERIC _UNIT_DISTANCE
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#pragma multi_compile _ _USE_DRAW_PROCEDURAL
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#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
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#include "Packages/com.unity.render-pipelines.universal/Shaders/PostProcessing/Common.hlsl"
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TEXTURE2D_X(_SourceTex);
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float4 _Params;
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// Back-ported & adapted from the work of the Stockholm demo team - thanks Lasse
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float2 Panini_UnitDistance(float2 view_pos)
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{
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// Given
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// S----------- E--X-------
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// | ` . /,´
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// |-- --- Q
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// 1 | ,´/ `
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// | ,´ / ´
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// | ,´ / `
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// | ,´ / .
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// O` / .
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// | / `
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// | / ´
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// 1 | / ´
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// | / ´
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// |/_ . ´
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// P
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//
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// Have E
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// Want to find X
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//
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// First apply tangent-secant theorem to find Q
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// PE*QE = SE*SE
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// QE = PE-PQ
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// PQ = PE-(SE*SE)/PE
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// Q = E*(PQ/PE)
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// Then project Q to find X
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const float d = 1.0;
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const float view_dist = 2.0;
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const float view_dist_sq = 4.0;
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float view_hyp = sqrt(view_pos.x * view_pos.x + view_dist_sq);
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float cyl_hyp = view_hyp - (view_pos.x * view_pos.x) / view_hyp;
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float cyl_hyp_frac = cyl_hyp / view_hyp;
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float cyl_dist = view_dist * cyl_hyp_frac;
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float2 cyl_pos = view_pos * cyl_hyp_frac;
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return cyl_pos / (cyl_dist - d);
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}
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float2 Panini_Generic(float2 view_pos, float d)
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{
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// Given
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// S----------- E--X-------
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// | ` ~. /,´
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// |-- --- Q
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// | ,/ `
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// 1 | ,´/ `
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// | ,´ / ´
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// | ,´ / ´
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// |,` / ,
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// O /
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// | / ,
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// d | /
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// | / ,
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// |/ .
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// P
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// | ´
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// | , ´
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// +- ´
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//
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// Have E
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// Want to find X
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//
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// First compute line-circle intersection to find Q
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// Then project Q to find X
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float view_dist = 1.0 + d;
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float view_hyp_sq = view_pos.x * view_pos.x + view_dist * view_dist;
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float isect_D = view_pos.x * d;
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float isect_discrim = view_hyp_sq - isect_D * isect_D;
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float cyl_dist_minus_d = (-isect_D * view_pos.x + view_dist * sqrt(isect_discrim)) / view_hyp_sq;
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float cyl_dist = cyl_dist_minus_d + d;
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float2 cyl_pos = view_pos * (cyl_dist / view_dist);
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return cyl_pos / (cyl_dist - d);
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}
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half4 Frag(Varyings input) : SV_Target
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{
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UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
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#if _GENERIC
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float2 proj_pos = Panini_Generic((2.0 * input.uv - 1.0) * _Params.xy * _Params.w, _Params.z);
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#else // _UNIT_DISTANCE
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float2 proj_pos = Panini_UnitDistance((2.0 * input.uv - 1.0) * _Params.xy * _Params.w);
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#endif
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float2 proj_ndc = proj_pos / _Params.xy;
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float2 coords = proj_ndc * 0.5 + 0.5;
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return SAMPLE_TEXTURE2D_X(_SourceTex, sampler_LinearClamp, coords);
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}
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ENDHLSL
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SubShader
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{
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Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline"}
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LOD 100
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ZTest Always ZWrite Off Cull Off
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Pass
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{
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Name "Panini Projection"
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HLSLPROGRAM
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#pragma vertex FullscreenVert
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#pragma fragment Frag
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ENDHLSL
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}
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}
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}
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