114 lines
4.1 KiB
Markdown
114 lines
4.1 KiB
Markdown
# URP unlit shader with color input
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The Unity shader in this example adds the __Base Color__ property to the Material. You can select the color using that property and the shader fills the mesh shape with the color.
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Use the Unity shader source file from section [URP unlit basic shader](writing-shaders-urp-basic-unlit-structure.md) and make the following changes to the ShaderLab code:
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1. Add the `_BaseColor` property definition to the Properties block:
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```c++
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Properties
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{
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[MainColor] _BaseColor("Base Color", Color) = (1, 1, 1, 1)
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}
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```
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This declaration adds the `_BaseColor` property with the label __Base Color__ to the Material:
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When you declare a property with the `[MainColor]` attribute, Unity uses this property as the [main color](https://docs.unity3d.com/ScriptReference/Material-color.html) of the Material.
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> **Note**: For compatibility reasons, the `_Color` property name is a reserved name. Unity uses a property with the name `_Color` as the [main color](https://docs.unity3d.com/ScriptReference/Material-color.html) even it does not have the `[MainColor]` attribute.
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2. When you declare a property in the Properties block, you also need to declare it in the HLSL code.
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> __NOTE__: To ensure that the Unity shader is SRP Batcher compatible, declare all Material properties inside a single `CBUFFER` block with the name `UnityPerMaterial`. For more information on the SRP Batcher, see the page [Scriptable Render Pipeline (SRP) Batcher](https://docs.unity3d.com/Manual/SRPBatcher.html).
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Add the following code before the vertex shader:
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```c++
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CBUFFER_START(UnityPerMaterial)
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half4 _BaseColor;
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CBUFFER_END
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```
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3. Change the code in the fragment shader so that it returns the `_BaseColor` property.
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```c++
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half4 frag() : SV_Target
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{
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return _BaseColor;
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}
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```
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Now you can select the color in the **Base Color** field in the Inspector window. The fragment shader fills the mesh with the color you select.
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Below is the complete ShaderLab code for this example.
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```c++
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// This shader fills the mesh shape with a color that a user can change using the
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// Inspector window on a Material.
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Shader "Example/URPUnlitShaderColor"
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{
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// The _BaseColor variable is visible in the Material's Inspector, as a field
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// called Base Color. You can use it to select a custom color. This variable
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// has the default value (1, 1, 1, 1).
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Properties
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{
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[MainColor] _BaseColor("Base Color", Color) = (1, 1, 1, 1)
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}
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SubShader
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{
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Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" }
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Pass
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{
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HLSLPROGRAM
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#pragma vertex vert
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#pragma fragment frag
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#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
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struct Attributes
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{
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float4 positionOS : POSITION;
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};
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struct Varyings
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{
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float4 positionHCS : SV_POSITION;
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};
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// To make the Unity shader SRP Batcher compatible, declare all
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// properties related to a Material in a a single CBUFFER block with
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// the name UnityPerMaterial.
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CBUFFER_START(UnityPerMaterial)
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// The following line declares the _BaseColor variable, so that you
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// can use it in the fragment shader.
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half4 _BaseColor;
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CBUFFER_END
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Varyings vert(Attributes IN)
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{
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Varyings OUT;
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OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
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return OUT;
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}
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half4 frag() : SV_Target
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{
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// Returning the _BaseColor value.
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return _BaseColor;
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}
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ENDHLSL
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}
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}
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}
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```
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Section [Drawing a texture](writing-shaders-urp-unlit-texture.md) shows how to draw a texture on the mesh.
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