Version: 2023.2
언어: 한국어
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DOTS 인스턴싱 셰이더

드로우 커맨드 생성

드로우 커맨드를 생성하려면 BatchRendererGroup.OnPerformCulling 콜백을 사용하십시오.구체적으로 말하자면 콜백의 BatchCullingOutput 파라미터를 사용합니다.이 파라미터에는 하나의 요소가 포함된 NativeArray가 있습니다.이 레이아웃을 통해 Unity가 불필요하게 데이터를 복사하지 않고도 배열 요소의 콘텐츠를 직접 수정할 수 있습니다.NativeArray의 요소는 실제 드로우 커맨드를 포함하는 BatchCullingOutputDrawCommands 구조체입니다.

OnPerformCulling을 구현하면 원하는 만큼의 드로우 커맨드를 생성할 수 있습니다.하나의 메시와 머티리얼만 사용하여 간단하게 구현하면 하나의 드로우 커맨드만 출력할 수 있지만, 각각 다른 메시와 머티리얼을 사용하여 더 복잡하게 구현하면 수천 개를 출력할 수 있습니다.

참고:최대한 유연하도록 Unity는 BatchCullingOutputDrawCommands 출력 구조체에 배열을 미리 할당하지 않고 원시 포인터로 저장하여 버스트 잡에서 쉽게 할당하고 사용할 수 있도록 합니다.Allocator.TempJob 할당자가 포함된 UnsafeUtility.Malloc을 사용하여 배열을 할당해야 합니다.콜백은 메모리를 해제하지 않아야 합니다.대신 Unity는 드로우 커맨드를 사용하여 렌더링을 완료한 후 메모리를 해제합니다.

드로우 커맨드 생성 방법의 예는 다음 코드 샘플을 참조하십시오.이 코드 샘플은 배치 생성에 있는 것을 기반으로 합니다.

using System;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using Unity.Jobs;
using UnityEngine;
using UnityEngine.Rendering;

public class SimpleBRGExample :MonoBehaviour
{
    public Mesh mesh;
    public Material material;

    private BatchRendererGroup m_BRG;

    private GraphicsBuffer m_InstanceData;
    private BatchID m_BatchID;
    private BatchMeshID m_MeshID;
    private BatchMaterialID m_MaterialID;

    // Some helper constants to make calculations more convenient.
    private const int kSizeOfMatrix = sizeof(float) * 4 * 4;
    private const int kSizeOfPackedMatrix = sizeof(float) * 4 * 3;
    private const int kSizeOfFloat4 = sizeof(float) * 4;
    private const int kBytesPerInstance = (kSizeOfPackedMatrix * 2) + kSizeOfFloat4;
    private const int kExtraBytes = kSizeOfMatrix * 2;
    private const int kNumInstances = 3;

    // The PackedMatrix is a convenience type that converts matrices into
    // the format that Unity-provided SRP shaders expect.
    struct PackedMatrix
    {
        public float c0x;
        public float c0y;
        public float c0z;
        public float c1x;
        public float c1y;
        public float c1z;
        public float c2x;
        public float c2y;
        public float c2z;
        public float c3x;
        public float c3y;
        public float c3z;

        public PackedMatrix(Matrix4x4 m)
        {
            c0x = m.m00;
            c0y = m.m10;
            c0z = m.m20;
            c1x = m.m01;
            c1y = m.m11;
            c1z = m.m21;
            c2x = m.m02;
            c2y = m.m12;
            c2z = m.m22;
            c3x = m.m03;
            c3y = m.m13;
            c3z = m.m23;
        }
    }

    private void Start()
    {
        m_BRG = new BatchRendererGroup(this.OnPerformCulling, IntPtr.Zero);
        m_MeshID = m_BRG.RegisterMesh(mesh);
        m_MaterialID = m_BRG.RegisterMaterial(material);

        AllocateInstanceDateBuffer();
        PopulateInstanceDataBuffer();
    }

    private void AllocateInstanceDateBuffer()
    {
        m_InstanceData = new GraphicsBuffer(GraphicsBuffer.Target.Raw,
            BufferCountForInstances(kBytesPerInstance, kNumInstances, kExtraBytes),
            sizeof(int));
    }

    private void PopulateInstanceDataBuffer()
    {
        // Place a zero matrix at the start of the instance data buffer, so loads from address 0 return zero.
        var zero = new Matrix4x4[1] { Matrix4x4.zero };

        // Create transform matrices for three example instances.
        var matrices = new Matrix4x4[kNumInstances]
        {
            Matrix4x4.Translate(new Vector3(-2, 0, 0)),
            Matrix4x4.Translate(new Vector3(0, 0, 0)),
            Matrix4x4.Translate(new Vector3(2, 0, 0)),
        };

        // Convert the transform matrices into the packed format that shaders expects.
        var objectToWorld = new PackedMatrix[kNumInstances]
        {
            new PackedMatrix(matrices[0]),
            new PackedMatrix(matrices[1]),
            new PackedMatrix(matrices[2]),
        };

        // Also create packed inverse matrices.
        var worldToObject = new PackedMatrix[kNumInstances]
        {
            new PackedMatrix(matrices[0].inverse),
            new PackedMatrix(matrices[1].inverse),
            new PackedMatrix(matrices[2].inverse),
        };

        // Make all instances have unique colors.
        var colors = new Vector4[kNumInstances]
        {
            new Vector4(1, 0, 0, 1),
            new Vector4(0, 1, 0, 1),
            new Vector4(0, 0, 1, 1),
        };

        // In this simple example, the instance data is placed into the buffer like this:
        // Offset | Description
        //      0 | 64 bytes of zeroes, so loads from address 0 return zeroes
        //     64 | 32 uninitialized bytes to make working with SetData easier, otherwise unnecessary
        //     96 | unity_ObjectToWorld, three packed float3x4 matrices
        //    240 | unity_WorldToObject, three packed float3x4 matrices
        //    384 | _BaseColor, three float4s

        // Calculates start addresses for the different instanced properties. unity_ObjectToWorld starts at 
        // address 96 instead of 64 which means 32 bits are left uninitialized.This is because the 
        // computeBufferStartIndex parameter requires the start offset to be divisible by the size of the source
        // array element type.In this case, it's the size of PackedMatrix, which is 48.
        uint byteAddressObjectToWorld = kSizeOfPackedMatrix * 2;
        uint byteAddressWorldToObject = byteAddressObjectToWorld + kSizeOfPackedMatrix * kNumInstances;
        uint byteAddressColor = byteAddressWorldToObject + kSizeOfPackedMatrix * kNumInstances;

        // Upload the instance data to the GraphicsBuffer so the shader can load them.
        m_InstanceData.SetData(zero, 0, 0, 1);
        m_InstanceData.SetData(objectToWorld, 0, (int)(byteAddressObjectToWorld / kSizeOfPackedMatrix), objectToWorld.Length);
        m_InstanceData.SetData(worldToObject, 0, (int)(byteAddressWorldToObject / kSizeOfPackedMatrix), worldToObject.Length);
        m_InstanceData.SetData(colors, 0, (int)(byteAddressColor / kSizeOfFloat4), colors.Length);

        // Set up metadata values to point to the instance data.Set the most significant bit 0x80000000 in each
        // which instructs the shader that the data is an array with one value per instance, indexed by the instance index.
        // Any metadata values that the shader uses and not set here will be zero.When such a value is used with
        // UNITY_ACCESS_DOTS_INSTANCED_PROP (i.e. without a default), the shader interprets the
        // 0x00000000 metadata value and loads from the start of the buffer.The start of the buffer which is
        // is a zero matrix so this sort of load is guaranteed to return zero, which is a reasonable default value.
        var metadata = new NativeArray<MetadataValue>(3, Allocator.Temp);
        metadata[0] = new MetadataValue { NameID = Shader.PropertyToID("unity_ObjectToWorld"), Value = 0x80000000 | byteAddressObjectToWorld, };
        metadata[1] = new MetadataValue { NameID = Shader.PropertyToID("unity_WorldToObject"), Value = 0x80000000 | byteAddressWorldToObject, };
        metadata[2] = new MetadataValue { NameID = Shader.PropertyToID("_BaseColor"), Value = 0x80000000 | byteAddressColor, };

        // Finally, create a batch for the instances, and make the batch use the GraphicsBuffer with the
        // instance data, as well as the metadata values that specify where the properties are.
        m_BatchID = m_BRG.AddBatch(metadata, m_InstanceData.bufferHandle);
    }

    // Raw buffers are allocated in ints.This is a utility method that calculates
    // the required number of ints for the data.
    int BufferCountForInstances(int bytesPerInstance, int numInstances, int extraBytes = 0)
    {
        // Round byte counts to int multiples
        bytesPerInstance = (bytesPerInstance + sizeof(int) - 1) / sizeof(int) * sizeof(int);
        extraBytes = (extraBytes + sizeof(int) - 1) / sizeof(int) * sizeof(int);
        int totalBytes = bytesPerInstance * numInstances + extraBytes;
        return totalBytes / sizeof(int);
    }


    private void OnDisable()
    {
        m_BRG.Dispose();
    }

    public unsafe JobHandle OnPerformCulling(
        BatchRendererGroup rendererGroup,
        BatchCullingContext cullingContext,
        BatchCullingOutput cullingOutput,
        IntPtr userContext)
    {
        // UnsafeUtility.Malloc() requires an alignment, so use the largest integer type's alignment
        // which is a reasonable default.
        int alignment = UnsafeUtility.AlignOf<long>();

        // Acquire a pointer to the BatchCullingOutputDrawCommands struct so you can easily
        // modify it directly.
        var drawCommands = (BatchCullingOutputDrawCommands*)cullingOutput.drawCommands.GetUnsafePtr();

        // Allocate memory for the output arrays.In a more complicated implementation, you would calculate
        // the amount of memory to allocate dynamically based on what is visible.
        // This example assumes that all of the instances are visible and thus allocates
        // memory for each of them.The necessary allocations are as follows:
        // - a single draw command (which draws kNumInstances instances)
        // - a single draw range (which covers our single draw command)
        // - kNumInstances visible instance indices.
        // You must always allocate the arrays using Allocator.TempJob.
        drawCommands->drawCommands = (BatchDrawCommand*)UnsafeUtility.Malloc(UnsafeUtility.SizeOf<BatchDrawCommand>(), alignment, Allocator.TempJob);
        drawCommands->drawRanges = (BatchDrawRange*)UnsafeUtility.Malloc(UnsafeUtility.SizeOf<BatchDrawRange>(), alignment, Allocator.TempJob);
        drawCommands->visibleInstances = (int*)UnsafeUtility.Malloc(kNumInstances * sizeof(int), alignment, Allocator.TempJob);
        drawCommands->drawCommandPickingInstanceIDs = null;

        drawCommands->drawCommandCount = 1;
        drawCommands->drawRangeCount = 1;
        drawCommands->visibleInstanceCount = kNumInstances;

        // This example doens't use depth sorting, so it leaves instanceSortingPositions as null.
        drawCommands->instanceSortingPositions = null;
        drawCommands->instanceSortingPositionFloatCount = 0;

        // Configure the single draw command to draw kNumInstances instances
        // starting from offset 0 in the array, using the batch, material and mesh
        // IDs registered in the Start() method.It doesn't set any special flags.
        drawCommands->drawCommands[0].visibleOffset = 0;
        drawCommands->drawCommands[0].visibleCount = kNumInstances;
        drawCommands->drawCommands[0].batchID = m_BatchID;
        drawCommands->drawCommands[0].materialID = m_MaterialID;
        drawCommands->drawCommands[0].meshID = m_MeshID;
        drawCommands->drawCommands[0].submeshIndex = 0;
        drawCommands->drawCommands[0].splitVisibilityMask = 0xff;
        drawCommands->drawCommands[0].flags = 0;
        drawCommands->drawCommands[0].sortingPosition = 0;

        // Configure the single draw range to cover the single draw command which
        // is at offset 0.
        drawCommands->drawRanges[0].drawCommandsBegin = 0;
        drawCommands->drawRanges[0].drawCommandsCount = 1;

        // This example doesn't care about shadows or motion vectors, so it leaves everything
        // at the default zero values, except the renderingLayerMask which it sets to all ones
        // so Unity renders the instances regardless of mask settings.
        drawCommands->drawRanges[0].filterSettings = new BatchFilterSettings { renderingLayerMask = 0xffffffff, };

        // Finally, write the actual visible instance indices to the array.In a more complicated
        // implementation, this output would depend on what is visible, but this example
        // assumes that everything is visible.
        for (int i = 0; i < kNumInstances; ++i)
            drawCommands->visibleInstances[i] = i;

        // This simple example doesn't use jobs, so it returns an empty JobHandle.
        // Performance-sensitive applications are encouraged to use Burst jobs to implement
        // culling and draw command output.In this case, this function returns a
        // handle here that completes when the Burst jobs finish.
        return new JobHandle();
    }
}

이는 BRG의 완성된 최종 코드 샘플입니다.이 컴포넌트를 게임 오브젝트에 연결하고 인스펙터에서 메시와 DOTS 인스턴싱 호환 머티리얼을 설정하고 플레이 모드로 들어가면, Unity가 머티리얼을 사용하여 메시의 인스턴스 3개를 렌더링합니다.

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