{"id":574,"date":"2019-12-05T02:28:23","date_gmt":"2019-12-05T02:28:23","guid":{"rendered":"https:\/\/www.danielparente.net\/en\/2019\/12\/05\/directional-lights\/"},"modified":"2019-12-05T02:28:23","modified_gmt":"2019-12-05T02:28:23","slug":"directional-lights","status":"publish","type":"post","link":"https:\/\/www.danielparente.net\/en\/2019\/12\/05\/directional-lights\/","title":{"rendered":"Directional Lights"},"content":{"rendered":"

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\n<\/p>\n

This is the third part of a tutorial series about creating a custom scriptable render pipeline<\/a>. It adds support for shading with multiple directional lights.<\/p>\n

This tutorial is made with Unity 2019.2.12f1.<\/p>\n

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Lighting<\/h2>\n

If we want to create a more realistic scene then we’ll have to simulate how light interacts with surfaces. This requires a more complex shader than the unlit one that we currently have.<\/p>\n

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Lit Shader<\/h3>\n

Duplicate the UnlitPass<\/em> HLSL file and rename it to LitPass<\/em>. Adjust the include guard define and the vertex and fragment function names to match. We’ll add lighting calculations later.<\/p>\n

#ifndef \n#define \n\n\u2026\n\nVaryings  (Attributes input) { \u2026 }\n\nfloat4  (Varyings input) : SV_TARGET { \u2026 }\n\n#endif<\/pre>\n
Also duplicate the Unlit<\/em> shader and rename it to Lit<\/em>. Change its menu name, the file it includes, and the functions it uses. Let’s also change the default color to gray, as a fully white surface in a well-lit scene can appear very bright. The Universal pipeline uses a gray color by default as well.<\/p>\n
Shader  {\n\t\n\tProperties {\n\t\t_BaseMap(\"Texture\", 2D) = \"white\" {}\n\t\t_BaseColor(\"Color\", Color) = (, 1.0)\n\t\t\u2026\n\t}\n\n\tSubShader {\n\t\tPass {\n\t\t\t\u2026\n\t\t\t#pragma vertex \n\t\t\t#pragma fragment \n\t\t\t#include \n\t\t\tENDHLSL\n\t\t}\n\t}\n}<\/pre>\n
We’re going to use a custom lighting approach, which we’ll indicate by setting the light mode of our shader to CustomLit<\/em>. Add a Tags<\/code> block to the Pass<\/code>, containing \"LightMode\" = \"CustomLit\"<\/code>.<\/p>\n
\t\tPass {\n\t\t\t\n\t\t\t\t\n\t\t\t\n\n\t\t\t\u2026\n\t\t}<\/pre>\n
To render objects that use this pass we have to include it in CameraRenderer<\/code>. First add a shader tag identifier for it.<\/p>\n
\tstatic ShaderTagId\n\t\tunlitShaderTagId = new ShaderTagId(\"SRPDefaultUnlit\")\n\t\t;<\/pre>\n
Then add it to the passes to be rendered in DrawVisibleGeometry<\/code>, like we did in DrawUnsupportedShaders<\/code>.<\/p>\n
\t\tvar drawingSettings = new DrawingSettings(\n\t\t\tunlitShaderTagId, sortingSettings\n\t\t) {\n\t\t\tenableDynamicBatching = useDynamicBatching,\n\t\t\tenableInstancing = useGPUInstancing\n\t\t};\n\t\t<\/pre>\n
Now we can create a new opaque material, though at this point it produces the same results an as unlit material.<\/p>\n
Default opaque material.<\/figcaption><\/figure>\n<\/section>\n
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Normal Vectors<\/h3>\n
How well an object is lit depends on multiple factors, including the relative angle between the light and surface. To know the surface’s orientation we need to access the surface normal, which is a unit-length vector pointing straight away from it. This vector is part of the vertex data, defined in object space just like the position. So add it to Attributes<\/code> in LitPass<\/em>.<\/p>\n
struct Attributes {\n\tfloat3 positionOS : POSITION;\n\t\n\tfloat2 baseUV : TEXCOORD0;\n\tUNITY_VERTEX_INPUT_INSTANCE_ID\n};<\/pre>\n
Lighting is calculated per fragment, so we have to add the normal vector to Varyings<\/code> as well. We’ll perform the calculations in world space, so name it normalWS<\/code>.<\/p>\n
struct Varyings {\n\tfloat4 positionCS : SV_POSITION;\n\t\n\tfloat2 baseUV : VAR_BASE_UV;\n\tUNITY_VERTEX_INPUT_INSTANCE_ID\n};<\/pre>\n
We can use TransformObjectToWorldNormal<\/code> from SpaceTransforms<\/em> to convert the normal to world space in LitPassVertex<\/code>.<\/p>\n
\toutput.positionWS = TransformObjectToWorld(input.positionOS);\n\toutput.positionCS = TransformWorldToHClip(positionWS);\n\t<\/pre>\n