From 40c37438cecb488ce7b601cdd9809b13064d980c Mon Sep 17 00:00:00 2001
From: parker <parker.g.britt@gmail.com>
Date: Sun, 3 Aug 2025 03:47:51 +0100
Subject: [PATCH] feat: multithread building vbo

---
 src/Engine/Operator/AttributeHandle.h |  2 +-
 src/Engine/Operator/Geometry.cpp      | 27 ++++-----
 src/Engine/Operator/Geometry.h        |  3 +-
 src/Gui/Viewport/GLMesh.cpp           | 81 ++++++++++++++-------------
 4 files changed, 59 insertions(+), 54 deletions(-)

diff --git a/src/Engine/Operator/AttributeHandle.h b/src/Engine/Operator/AttributeHandle.h
index a2bcc87..e3e0a49 100644
--- a/src/Engine/Operator/AttributeHandle.h
+++ b/src/Engine/Operator/AttributeHandle.h
@@ -75,7 +75,7 @@ public:
     {
         // TODO:protect against invalid positions
         // TODO: cast types
-        return data_[pos];
+        return (*data_)[pos];
     }
 
     void setValue(size_t pos, const T& value)
diff --git a/src/Engine/Operator/Geometry.cpp b/src/Engine/Operator/Geometry.cpp
index 03228f6..069fb3e 100644
--- a/src/Engine/Operator/Geometry.cpp
+++ b/src/Engine/Operator/Geometry.cpp
@@ -170,24 +170,25 @@ enzo::geo::HeMesh geo::Geometry::computeHalfEdgeMesh()
     return heMesh;
 }
 
-unsigned int geo::Geometry::getPrimStartVertex(ga::Offset primOffset)
+ga::Offset geo::Geometry::getPrimStartVertex(ga::Offset primOffset) const
 {
-    const ga::Offset handleSize = vertexCountHandlePrim_.getSize();
-    // TODO: add smarter system to recompute primStarts_, also move to separate function 
-    // if size changed, recompute
-    if(handleSize!=primStarts_.size())
-    {
-        bt::intT primStart = 0;
-        for(size_t i=0; i<handleSize; ++i)
-        {
-            primStarts_.push_back(primStart);
-            primStart += vertexCountHandlePrim_.getValue(i);
-        }
-    }
 
     return primStarts_[primOffset];
 }
 
+// TODO: handle this automatically
+void geo::Geometry::computePrimStartVertices()
+{
+    const ga::Offset handleSize = vertexCountHandlePrim_.getSize();
+    bt::intT primStart = 0;
+    for(size_t i=0; i<handleSize; ++i)
+    {
+        primStarts_.push_back(primStart);
+        primStart += vertexCountHandlePrim_.getValue(i);
+    }
+}
+
+
 
 
 ga::AttributeHandle<int> geo::Geometry::addIntAttribute(ga::AttributeOwner owner, std::string name)
diff --git a/src/Engine/Operator/Geometry.h b/src/Engine/Operator/Geometry.h
index eb97fb8..833c97e 100644
--- a/src/Engine/Operator/Geometry.h
+++ b/src/Engine/Operator/Geometry.h
@@ -31,14 +31,15 @@ public:
     std::vector<bt::Vector3> derivePointNormals();
     HeMesh computeHalfEdgeMesh();
     // returns the first vertex of the primitive
-    unsigned int getPrimStartVertex(ga::Offset primOffset);
     void addFace(std::initializer_list<ga::Offset> pointOffsets);
 
+    ga::Offset getPrimStartVertex(ga::Offset primOffset) const;
     bt::Vector3 getPosFromVert(ga::Offset vertexOffset) const;
     bt::Vector3 getPointPos(ga::Offset pointOffset) const;
     unsigned int getPrimVertCount(ga::Offset primOffset) const;
     ga::Offset getNumPrims() const;
     ga::Offset getNumVerts() const;
+    void computePrimStartVertices();
 private:
     using attribVector = std::vector<std::shared_ptr<ga::Attribute>>;
     attribVector& getAttributeStore(ga::AttributeOwner& owner);
diff --git a/src/Gui/Viewport/GLMesh.cpp b/src/Gui/Viewport/GLMesh.cpp
index 2078ade..46a9d61 100644
--- a/src/Gui/Viewport/GLMesh.cpp
+++ b/src/Gui/Viewport/GLMesh.cpp
@@ -5,6 +5,8 @@
 #include "Engine/Operator/Geometry.h"
 #include "Engine/Types.h"
 #include <CGAL/Polygon_mesh_processing/compute_normal.h>
+#include <oneapi/tbb/blocked_range.h>
+#include <oneapi/tbb/parallel_for.h>
 #include "icecream.hpp"
 
 
@@ -61,53 +63,54 @@ void GLMesh::setPosBuffer(enzo::geo::Geometry& geometry)
     const size_t numPrims = geometry.getNumPrims();
 
     vertices.resize(geometry.getNumVerts());
+    geometry.computePrimStartVertices();
 
-
-    for (int primOffset=0; primOffset<numPrims; ++primOffset)
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, numPrims), [&](tbb::blocked_range<size_t> range)
     {
-        const unsigned int primStartVert = geometry.getPrimStartVertex(primOffset);
-        auto faceIndex = primOffset;
-        
-        int faceVertCnt = geometry.getPrimVertCount(primOffset);
-
-        enzo::bt::Vector3 n;
-
-        // compute normal
-        if(faceVertCnt>=3)
+        for (int primOffset=range.begin(); primOffset<range.end(); ++primOffset)
         {
-            const unsigned v1 = primStartVert;
-            const unsigned v2 = primStartVert + 1;
-            const unsigned v3 = primStartVert + 2;
+            const enzo::ga::Offset primStartVert = geometry.getPrimStartVertex(primOffset);
+            const unsigned int faceVertCnt = geometry.getPrimVertCount(primOffset);
 
-            const enzo::bt::Vector3 pos1 = geometry.getPosFromVert(v1);
-            const enzo::bt::Vector3 pos2 = geometry.getPosFromVert(v2);
-            const enzo::bt::Vector3 pos3 = geometry.getPosFromVert(v3);
+            enzo::bt::Vector3 Normal;
 
-            enzo::bt::Vector3 tang1 = (pos2-pos1);
-            enzo::bt::Vector3 tang2 = (pos3-pos1);
+            // compute normal
+            if(faceVertCnt>=3)
+            {
+                const unsigned v1 = primStartVert;
+                const unsigned v2 = primStartVert + 1;
+                const unsigned v3 = primStartVert + 2;
 
-            tang1.normalize();
-            tang2.normalize();
+                const enzo::bt::Vector3 pos1 = geometry.getPosFromVert(v1);
+                const enzo::bt::Vector3 pos2 = geometry.getPosFromVert(v2);
+                const enzo::bt::Vector3 pos3 = geometry.getPosFromVert(v3);
+
+                enzo::bt::Vector3 tang1 = (pos2-pos1);
+                enzo::bt::Vector3 tang2 = (pos3-pos1);
+
+                tang1.normalize();
+                tang2.normalize();
+
+                Normal = tang1.cross(tang2);
+            }
+
+            for(int i=0; i< faceVertCnt; ++i)
+            {
+                const unsigned int vertexCount = primStartVert+i;
+                enzo::bt::Vector3 p = geometry.getPosFromVert(vertexCount);
+
+                vertices[vertexCount] ={
+                    { p.x(),
+                      p.y(),
+                      p.z()},
+                    { Normal.x(),
+                      Normal.y(),
+                      Normal.z()}
+                };
+            }
 
-            n = tang1.cross(tang2);
         }
-
-        for(int i=0; i< faceVertCnt; ++i)
-        {
-            const unsigned int vertexCount = primStartVert+i;
-            enzo::bt::Vector3 p = geometry.getPosFromVert(vertexCount);
-
-            vertices[vertexCount] ={
-                { p.x(),
-                  p.y(),
-                  p.z()},
-                { n.x(),
-                  n.y(),
-                  n.z()}
-            };
-        }
-
-    }
+    });
 
     glBufferData(GL_ARRAY_BUFFER, vertices.size()*sizeof(Vertex), vertices.data(), GL_STATIC_DRAW);
     unbind();