TriAxis-Games#281 A couple of the old samples but using the new code

Source/RealtimeMeshExamples/Private/RealtimeMeshBranchingLinesActor.cpp

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+// Copyright TriAxis Games, L.L.C. & xixgames All Rights Reserved.
+
+#include "RealtimeMeshBranchingLinesActor.h"
+
+#include "RealtimeMeshSimple.h"
+
+ARealtimeMeshBranchingLinesActor::ARealtimeMeshBranchingLinesActor()
+{
+	PrimaryActorTick.bCanEverTick = false;
+}
+
+void ARealtimeMeshBranchingLinesActor::OnGenerateMesh_Implementation()
+{
+	// Initialize to a simple mesh, this behaves the most like a ProceduralMeshComponent
+	// Where you can set the mesh data and forget about it.
+	URealtimeMeshSimple* RealtimeMesh = GetRealtimeMeshComponent()->InitializeRealtimeMesh<URealtimeMeshSimple>();
+
+	// The most important part of the mesh data is the StreamSet, it contains the individual buffers,
+	// like position, tangents, texcoords, triangles etc. 
+	FRealtimeMeshStreamSet StreamSet;
+
+	// For this example we'll use a helper class to build the mesh data
+	// You can make your own helpers or skip them and use individual TRealtimeMeshStreamBuilder,
+	// or skip them entirely and copy data directly into the streams
+	TRealtimeMeshBuilderLocal<uint16, FPackedNormal, FVector2DHalf, 1> Builder(StreamSet);
+
+	// here we go ahead and enable all the basic mesh data parts
+	Builder.EnableTangents();
+	Builder.EnableTexCoords();
+	Builder.EnableColors(); // TODO
+
+	// Poly groups allow us to easily create a single set of buffers with multiple sections by adding an index to the triangle data
+	Builder.EnablePolyGroups();
+
+	// CUSTOM BUILD OF THE BRANCHES
+	PreCacheCrossSection();
+	GenerateMesh(Builder);
+
+	// Setup the two material slots
+	RealtimeMesh->SetupMaterialSlot(0, "PrimaryMaterial", Material);
+	//RealtimeMesh->SetupMaterialSlot(1, "SecondaryMaterial");
+
+	// Now create the group key. This is a unique identifier for the section group
+	// A section group contains one or more sections that all share the underlying buffers
+	// these sections can overlap the used vertex/index ranges depending on use case.
+	const FRealtimeMeshSectionGroupKey GroupKey = FRealtimeMeshSectionGroupKey::Create(0, FName("TestTriangle"));
+
+	// Now create the section key, this is a unique identifier for a section within a group
+	// The section contains the configuration for the section, like the material slot,
+	// and the draw type, as well as the range of the index/vertex buffers to use to render.
+	// Here we're using the version to create the key based on the PolyGroup index
+	const FRealtimeMeshSectionKey PolyGroup0SectionKey = FRealtimeMeshSectionKey::CreateForPolyGroup(GroupKey, 0);
+	//const FRealtimeMeshSectionKey PolyGroup1SectionKey = FRealtimeMeshSectionKey::CreateForPolyGroup(GroupKey, 1);
+
+	// Now we create the section group, since the stream set has polygroups, this will create the sections as well
+	RealtimeMesh->CreateSectionGroup(GroupKey, StreamSet);
+
+	// Update the configuration of both the polygroup sections.
+	RealtimeMesh->UpdateSectionConfig(PolyGroup0SectionKey, FRealtimeMeshSectionConfig(ERealtimeMeshSectionDrawType::Static, 0));
+	//RealtimeMesh->UpdateSectionConfig(PolyGroup1SectionKey, FRealtimeMeshSectionConfig(ERealtimeMeshSectionDrawType::Static, 1));
+
+	Super::OnGenerateMesh_Implementation();
+}
+
+void ARealtimeMeshBranchingLinesActor::GenerateMesh(RealtimeMesh::TRealtimeMeshBuilderLocal<uint16, FPackedNormal, FVector2DHalf, 1>& Builder)
+{
+	// -------------------------------------------------------
+	// Setup the random number generator and create the branching structure
+	RngStream.Initialize(RandomSeed);
+	CreateSegments();
+
+	// -------------------------------------------------------
+	// Now lets loop through all the defined segments and create a cylinder for each
+	for (int32 i = 0; i < Segments.Num(); i++)
+	{
+		GenerateCylinder(Segments[i].Start, Segments[i].End, Segments[i].Width,
+						 RadialSegmentCount, Builder, bSmoothNormals);
+	}
+}
+
+FVector ARealtimeMeshBranchingLinesActor::RotatePointAroundPivot(const FVector& InPoint, const FVector& InPivot, const FVector& InAngles)
+{
+	FVector Direction = InPoint - InPivot; // get point direction relative to pivot
+	Direction = FQuat::MakeFromEuler(InAngles) * Direction; // rotate it
+	return Direction + InPivot; // calculate rotated point
+}
+
+void ARealtimeMeshBranchingLinesActor::PreCacheCrossSection()
+{
+	if (LastCachedCrossSectionCount == RadialSegmentCount)
+	{
+		return;
+	}
+
+	// Generate a cross-section for use in cylinder generation
+	const float AngleBetweenQuads = (2.0f / static_cast<float>(RadialSegmentCount)) * PI;
+	CachedCrossSectionPoints.Empty();
+
+	// Pre-calculate cross section points of a circle, two more than needed
+	for (int32 PointIndex = 0; PointIndex < (RadialSegmentCount + 2); PointIndex++)
+	{
+		const float Angle = static_cast<float>(PointIndex) * AngleBetweenQuads;
+		CachedCrossSectionPoints.Add(FVector(FMath::Cos(Angle), FMath::Sin(Angle), 0));
+	}
+
+	LastCachedCrossSectionCount = RadialSegmentCount;
+}
+
+void ARealtimeMeshBranchingLinesActor::CreateSegments()
+{
+	// We create the branching structure by constantly subdividing a line between two points by creating a new point in the middle.
+	// We then take that point and offset it in a random direction, by a random amount defined within limits.
+	// Next we take both of the newly created line halves, and subdivide them the same way.
+	// Each new midpoint also has a chance to create a new branch
+	// TODO This should really be recursive
+	Segments.Empty();
+	float CurrentBranchOffset = MaxBranchOffset;
+
+	if (bMaxBranchOffsetAsPercentageOfLength)
+	{
+		CurrentBranchOffset = (Start - End).Size() * (FMath::Clamp(MaxBranchOffset, 0.1f, 100.0f) / 100.0f);
+	}
+
+	// Pre-calc a few floats from percentages
+	const float ChangeOfFork = FMath::Clamp(ChanceOfForkPercentage, 0.0f, 100.0f) / 100.0f;
+	const float BranchOffsetReductionEachGeneration = FMath::Clamp(BranchOffsetReductionEachGenerationPercentage, 0.0f, 100.0f) / 100.0f;
+
+	// Add the first segment which is simply between the start and end points
+	Segments.Add(FRealtimeMeshBranchSegment(Start, End, TrunkWidth));
+
+	for (int32 iGen = 0; iGen < Iterations; iGen++)
+	{
+		TArray<FRealtimeMeshBranchSegment> NewGen;
+
+		for (const FRealtimeMeshBranchSegment& EachSegment : Segments)
+		{
+			FVector Midpoint = (EachSegment.End + EachSegment.Start) / 2;
+
+			// Offset the midpoint by a random number along the normal
+			const FVector Normal = FVector::CrossProduct(EachSegment.End - EachSegment.Start, OffsetDirections[RngStream.RandRange(0, 1)]).GetSafeNormal();
+			Midpoint += Normal * RngStream.RandRange(-CurrentBranchOffset, CurrentBranchOffset);
+
+			 // Create two new segments
+			NewGen.Add(FRealtimeMeshBranchSegment(EachSegment.Start, Midpoint, EachSegment.Width, EachSegment.ForkGeneration));
+			NewGen.Add(FRealtimeMeshBranchSegment(Midpoint, EachSegment.End, EachSegment.Width, EachSegment.ForkGeneration));
+
+			// Chance of fork?
+			if (RngStream.FRand() > (1 - ChangeOfFork))
+			{
+				// TODO Normalize the direction vector and calculate a new total length and then subdiv that for X generations
+				const FVector Direction = Midpoint - EachSegment.Start;
+				const FVector SplitEnd = (Direction * RngStream.FRandRange(ForkLengthMin, ForkLengthMax)).RotateAngleAxis(RngStream.FRandRange(ForkRotationMin, ForkRotationMax), OffsetDirections[RngStream.RandRange(0, 1)]) + Midpoint;
+				NewGen.Add(FRealtimeMeshBranchSegment(Midpoint, SplitEnd, EachSegment.Width * WidthReductionOnFork, EachSegment.ForkGeneration + 1));
+			}
+		}
+
+		Segments.Empty();
+		Segments = NewGen;
+
+		// Reduce the offset slightly each generation
+		CurrentBranchOffset = CurrentBranchOffset * BranchOffsetReductionEachGeneration;
+	}
+}
+
+void ARealtimeMeshBranchingLinesActor::GenerateCylinder(const FVector& StartPoint, const FVector& EndPoint, const float InWidth,
+    const int32 InCrossSectionCount, TRealtimeMeshBuilderLocal<uint16, FPackedNormal, FVector2DHalf, 1>& Builder,
+    const bool bInSmoothNormals/* = true*/)
+{
+    // Make a cylinder section
+    const float AngleBetweenQuads = (2.0f / static_cast<float>(InCrossSectionCount)) * PI;
+    const float UMapPerQuad = 1.0f / static_cast<float>(InCrossSectionCount);
+
+    const FVector StartOffset = StartPoint - FVector(0, 0, 0);
+    const FVector Offset = EndPoint - StartPoint;
+
+    // Find angle between vectors
+    const FVector LineDirection = (StartPoint - EndPoint).GetSafeNormal();
+    const FVector RotationAngle = LineDirection.Rotation().Add(90.f, 0.f, 0.f).Euler();
+
+    // Start by building up vertices that make up the cylinder sides
+    for (int32 QuadIndex = 0; QuadIndex < InCrossSectionCount; QuadIndex++)
+    {
+        // Set up the vertices
+        FVector P0 = (CachedCrossSectionPoints[QuadIndex] * InWidth) + StartOffset;
+        P0 = RotatePointAroundPivot(P0, StartPoint, RotationAngle);
+        FVector P1 = CachedCrossSectionPoints[QuadIndex + 1] * InWidth + StartOffset;
+        P1 = RotatePointAroundPivot(P1, StartPoint, RotationAngle);
+        const FVector P2 = P1 + Offset;
+        const FVector P3 = P0 + Offset;
+
+        // Normals
+        const FVector NormalCurrent = FVector::CrossProduct(P0 - P3, P1 - P3).GetSafeNormal();
+        FVector NormalNext, NormalPrevious, AverageNormalRight, AverageNormalLeft;
+        if (bInSmoothNormals)
+        {
+            FVector P4 = (CachedCrossSectionPoints[QuadIndex + 2] * InWidth) + StartOffset;
+            P4 = RotatePointAroundPivot(P4, StartPoint, RotationAngle);
+
+            // p1 to p4 to p2
+            NormalNext = FVector::CrossProduct(P1 - P2, P4 - P2).GetSafeNormal();
+            AverageNormalRight = ((NormalCurrent + NormalNext) / 2).GetSafeNormal();
+
+            const float PreviousAngle = static_cast<float>(QuadIndex - 1) * AngleBetweenQuads;
+            FVector PMinus1 = FVector(FMath::Cos(PreviousAngle) * InWidth, FMath::Sin(PreviousAngle) * InWidth, 0.f) + StartOffset;
+            PMinus1 = RotatePointAroundPivot(PMinus1, StartPoint, RotationAngle);
+
+            // p0 to p3 to pMinus1
+            NormalPrevious = FVector::CrossProduct(P0 - PMinus1, P3 - PMinus1).GetSafeNormal();
+            AverageNormalLeft = ((NormalCurrent + NormalPrevious) / 2).GetSafeNormal();
+        }
+
+        // Tangents (perpendicular to the surface)
+        const FVector Tangent = (P0 - P1).GetSafeNormal();
+
+        // UVs
+        const FVector2D UV0 = FVector2D(1.0f - (UMapPerQuad * QuadIndex), 1.0f);
+        const FVector2D UV1 = FVector2D(1.0f - (UMapPerQuad * (QuadIndex + 1)), 1.0f);
+        const FVector2D UV2 = FVector2D(1.0f - (UMapPerQuad * (QuadIndex + 1)), 0.0f);
+        const FVector2D UV3 = FVector2D(1.0f - (UMapPerQuad * QuadIndex), 0.0f);
+
+        const int32 V0 = Builder.AddVertex(static_cast<FVector3f>(P0))
+            .SetNormalAndTangent(static_cast<FVector3f>(bInSmoothNormals ? AverageNormalLeft : NormalCurrent), static_cast<FVector3f>(Tangent))
+            .SetTexCoord(static_cast<FVector2f>(UV0));
+        const int32 V1 = Builder.AddVertex(static_cast<FVector3f>(P1))
+            .SetNormalAndTangent(static_cast<FVector3f>(bInSmoothNormals ? AverageNormalRight : NormalCurrent), static_cast<FVector3f>(Tangent))
+            .SetTexCoord(static_cast<FVector2f>(UV1));
+        const int32 V2 = Builder.AddVertex(static_cast<FVector3f>(P2))
+            .SetNormalAndTangent(static_cast<FVector3f>(bInSmoothNormals ? AverageNormalRight : NormalCurrent), static_cast<FVector3f>(Tangent))
+            .SetTexCoord(static_cast<FVector2f>(UV2));
+        const int32 V3 = Builder.AddVertex(static_cast<FVector3f>(P3))
+            .SetNormalAndTangent(static_cast<FVector3f>(bInSmoothNormals ? AverageNormalLeft : NormalCurrent), static_cast<FVector3f>(Tangent))
+            .SetTexCoord(static_cast<FVector2f>(UV3));
+
+        // Add our 2 triangles, placing the vertices in counter clockwise order
+        Builder.AddTriangle(V3, V2, V0, 0);
+        Builder.AddTriangle(V2, V1, V0, 0);
+    }
+}