ScriptableRenderPipeline/MaterialGraphProject/Assets/_MingWai/ScatterNode.cs

using UnityEngine.Graphing;

namespace UnityEngine.MaterialGraph
{
    [Title("Procedural/Scatter")]
    public class ScatterNode : FunctionNInNOut, IGeneratesFunction
    {

        [SerializeField]
        private int m_num = 1 ;


        public int num
        {
            get { return m_num; }
            set
            {

                if (m_num == value)
                {
                    return;
                }

                m_num = value;
                if (onModified != null)
                {
                    onModified(this, ModificationScope.Graph);
                }
            }
        }

        public ScatterNode()
        {
            name = "Scatter";
            AddSlot("Texture", "inputTex", Graphing.SlotType.Input, SlotValueType.sampler2D, Vector4.zero);
            AddSlot("UV", "inputUV", Graphing.SlotType.Input, SlotValueType.Vector2, Vector2.one);
            AddSlot("Seed", "seed", Graphing.SlotType.Input, SlotValueType.Vector2, Vector2.one);
            AddSlot("PositionRange", "p_range", Graphing.SlotType.Input, SlotValueType.Vector2, Vector2.zero);
            AddSlot("RotationRange", "r_range", Graphing.SlotType.Input, SlotValueType.Vector2, Vector2.zero);
            AddSlot("ScaleRange", "s_range", Graphing.SlotType.Input, SlotValueType.Vector2, Vector2.zero);
            AddSlot("RGBA", "finalColor", Graphing.SlotType.Output, SlotValueType.Vector4, Vector4.zero);
            UpdateNodeAfterDeserialization();
        }

        protected override string GetFunctionName()
        {
            return "unity_scatter_" + precision;
        }

        public override bool hasPreview
        {
            get { return true; }
        }

        public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
        {
            var outputString = new ShaderGenerator();

            //RotateUVFunction ===================================================================
            outputString.AddShaderChunk("inline float2 rotateUV( float2 arg1, float arg2 )", false);
            outputString.AddShaderChunk("{", false);
            outputString.Indent();
            //center texture's pivot
            outputString.AddShaderChunk("arg1.xy -= 0.5;", false);
            //rotation matrix
            outputString.AddShaderChunk(precision + " s = sin(arg2);", false);
            outputString.AddShaderChunk(precision + " c = cos(arg2);", false);
            outputString.AddShaderChunk(precision + "2x2 rMatrix = float2x2(c, -s, s, c);", false);
            //center rotation matrix
            outputString.AddShaderChunk("rMatrix *= 0.5;", false);
            outputString.AddShaderChunk("rMatrix += 0.5;", false);
            outputString.AddShaderChunk("rMatrix = rMatrix*2 - 1;", false);
            //multiply the UVs by the rotation matrix
            outputString.AddShaderChunk("arg1.xy = mul(arg1.xy, rMatrix);", false);
            outputString.AddShaderChunk("arg1.xy += 0.5;", false);
            outputString.AddShaderChunk("return " + "arg1;", false);
            outputString.Deindent();
            outputString.AddShaderChunk("}", false);

            //RamdomFunction ===================================================================
            outputString.AddShaderChunk("inline float randomrange(float2 randomseed, float min, float max)", false);
            outputString.AddShaderChunk("{", false);
            outputString.Indent();
            outputString.AddShaderChunk("float randomno =  frac(sin(dot(randomseed, float2(12.9898, 78.233)))*43758.5453);", false);
            outputString.AddShaderChunk("return floor(randomno * (max - min + 1)) + min;", false);
            outputString.Deindent();
            outputString.AddShaderChunk("}", false);

            //ScatterFunction ===================================================================
            outputString.AddShaderChunk(GetFunctionPrototype(), false);
            outputString.AddShaderChunk("{", false);
            outputString.Indent();

            outputString.AddShaderChunk("finalColor = float4(0,0,0,0);", false);
            outputString.AddShaderChunk("float2 newuv = inputUV;", false);
            outputString.AddShaderChunk("float4 tex = tex2D(inputTex,newuv);", false);
            
            for (int i=0; i<m_num; i++)
            {
                //random UV
                outputString.AddShaderChunk("newuv *= randomrange(seed,s_range.x,s_range.y);", false); //Scale
                outputString.AddShaderChunk("newuv = rotateUV(newuv,randomrange(seed,r_range.x,r_range.y));", false); //Rotate
                outputString.AddShaderChunk("newuv += randomrange(seed,p_range.x,p_range.y));", false); //Position

                //seamless


                //sample
                outputString.AddShaderChunk("tex = tex2D(inputTex,newuv);", false);

                //blend together
                outputString.AddShaderChunk("finalColor += tex/"+m_num+";", false);
            }

            outputString.Deindent();
            outputString.AddShaderChunk("}", false);

            visitor.AddShaderChunk(outputString.GetShaderString(0), true);
        }
    }
}