Unity HLSL Shader 序列帧动画V0.1

目标：

Unity 序列帧动画shader

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步骤：

1. 定义序列帧图的行数和列数

   	_RowNums	("Row Nums",	float) = 0
   	_ColumnNums ("Column Nums",	float) = 0
   

2. 定义帧数的位置（这样做方便直接脚本控制或者animation控制）

   	_FrameIndex ("FrameIndex",  Range(0, 1)) = 0
   

3. uv查找算法

   	float r = floor(_RowNums);
   	float c = floor(_ColumnNums);
   	float sizeX = 1.0f / c;
   	float sizeY = 1.0f / r;
   	float frameIndex = floor((r * c - 1) * _FrameIndex);
   
   	float2 uv     = float2(IN.uv.x, IN.uv.y) / float2(c, r);
   	float2 offset = float2(0, 0);
   	offset.x = (frameIndex % c) * sizeX;
   	offset.y = 1 - sizeY - floor(frameIndex / r) * sizeY;
   

4. 完整shader

   Shader "FramePlayer" {
   	Properties {
   		[NoScaleOffset]_BaseMap (" Texture", 2D) = "white" {}
   	
   		_RowNums	("Row Nums",	float) = 0
   		_ColumnNums ("Column Nums",	float) = 0
   		_FrameIndex ("FrameIndex",  Range(0, 1)) = 0
   	}
   	SubShader {
   		Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" }
   
   		HLSLINCLUDE
   		#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
   
   		CBUFFER_START(UnityPerMaterial)
   		float4 _BaseColor;
   
   		float _RowNums;
   		float _ColumnNums;
   		float _FrameIndex;
   	
   		CBUFFER_END
   		ENDHLSL
   
   	Pass {
   		Name "Example"
   		Tags { "LightMode"="UniversalForward" "Queue"="Transparent"}
   		Blend SrcAlpha OneMinusSrcAlpha
   
   		HLSLPROGRAM
   			#pragma vertex vert
   			#pragma fragment frag
   
   			struct Attributes {
   				float4 positionOS	: POSITION;
   				float2 uv			: TEXCOORD0;
   			};
   
   			struct Varyings {
   				float4 positionCS 	: SV_POSITION;
   				float2 uv			: TEXCOORD0;
   			};
   
   			TEXTURE2D(_BaseMap);	SAMPLER(sampler_BaseMap);
   
   			Varyings vert(Attributes IN) {
   				Varyings OUT;
   
   				VertexPositionInputs positionInputs = GetVertexPositionInputs(IN.positionOS.xyz);
   
   				OUT.positionCS = positionInputs.positionCS;
   				OUT.uv = IN.uv;
   
   				return OUT;
   			}
   
   			half4 frag(Varyings IN) : SV_Target {
   
   				float r = floor(_RowNums);
   				float c = floor(_ColumnNums);
   				float sizeX = 1.0f / c;
   				float sizeY = 1.0f / r;
   				float frameIndex = floor((r * c - 1) * _FrameIndex);
   
   				float2 uv     = float2(IN.uv.x, IN.uv.y) / float2(c, r);
   				float2 offset = float2(0, 0);
   				offset.x = (frameIndex % c) * sizeX;
   				offset.y = 1 - sizeY - floor(frameIndex / r) * sizeY;
   			
   				half4 baseMap = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, uv + offset);
   
   				return baseMap;
   			}
   			ENDHLSL
   		}
   	}
   }
   

5. 总结：一个方便脚本控制的序列帧shader