Extend face controller to support splitting a face along a plane

Individual parts of the splits faces can then be styled separately

3 files changed, 98 insertions, 9 deletions

diff --git a/assetFactory/faceController.cpp b/assetFactory/faceController.cpp
index 25bf833..28812d8 100644
--- a/assetFactory/faceController.cpp
+++ b/assetFactory/faceController.cpp
@@ -2,6 +2,7 @@
 #include "collections.hpp"
 #include "maths.h"
 #include "modelFactoryMesh.h"
+#include <glm/gtx/intersect.hpp>
 
 void
 FaceController::apply(ModelFactoryMesh & mesh, const StyleStack & parents, const std::string & names,
@@ -30,24 +31,29 @@ void
 FaceController::applySingle(ModelFactoryMesh & mesh, const StyleStack & parents, const std::string & name,
 		Shape::CreatedFaces & faces) const
 {
-	const auto controlledFaces {materializeRange(faces.equal_range(name))};
-	if (controlledFaces.empty()) {
-		throw std::runtime_error("Named face(s) do not exist: " + name);
-	}
+	auto controlledFaces {materializeRange(faces.equal_range(name))};
 
-	if (!type.empty()) {
+	if (!type.empty() || !splits.empty()) {
 		faces.erase(name);
 	}
-	for (const auto & [faceName, faceHandle] : controlledFaces) {
+	for (auto & [faceName, faceHandle] : controlledFaces) {
+		Shape::CreatedFaces newFaces;
+		for (const auto & [newFaceSuffix, splitDef] : splits) {
+			newFaces.merge(split(mesh, name + newFaceSuffix, faceHandle, *splitDef));
+		}
 		if (type == "extrude") {
-			auto newFaces = extrude(mesh, faceName, faceHandle);
+			newFaces.merge(extrude(mesh, name, faceHandle));
+		}
+		if (!newFaces.empty()) {
 			applyStyle(mesh, parents + this, newFaces);
 			for (const auto & [subFaceName, faceController] : faceControllers) {
 				faceController->apply(mesh, parents + this, subFaceName, newFaces);
 			}
 			faces.merge(std::move(newFaces));
 		}
-		applyStyle(mesh, parents + this, faceHandle);
+		else {
+			applyStyle(mesh, parents + this, faceHandle);
+		}
 	}
 }
 
@@ -88,9 +94,70 @@ FaceController::extrude(ModelFactoryMesh & mesh, const std::string & faceName, O
 	return newFaces;
 }
 
+enum class PlaneRelation { Above, Below, On };
+Shape::CreatedFaces
+FaceController::split(
+		ModelFactoryMesh & mesh, const std::string & name, OpenMesh::FaceHandle & fh, const Split & split) const
+{
+	// Map face vertex handles to their relationship to the split plane
+	const auto vertices = materializeRange(mesh.fv_range(fh));
+	auto vertexRelations = vertices * [&split, &mesh](OpenMesh::VertexHandle vh) {
+		const auto d = glm::dot(split.normal, mesh.point(vh) - split.origin);
+		return std::make_pair(vh, d < 0.f ? PlaneRelation::Below : d > 0.f ? PlaneRelation::Above : PlaneRelation::On);
+	};
+	// Insert new vertices where half edges intersect the split plane
+	for (size_t curIdx = 0; curIdx < vertexRelations.size(); ++curIdx) {
+		const size_t nextIdx = (curIdx + 1) % vertexRelations.size();
+		const auto &current = vertexRelations[curIdx], next = vertexRelations[nextIdx];
+		if ((current.second == PlaneRelation::Above && next.second == PlaneRelation::Below)
+				|| (current.second == PlaneRelation::Below && next.second == PlaneRelation::Above)) {
+			const auto origin = mesh.point(current.first), dir = glm::normalize(mesh.point(next.first) - origin);
+
+			float dist {};
+			glm::intersectRayPlane(origin, dir, split.origin, split.normal, dist);
+			const auto newv = mesh.add_vertex(origin + (dir * dist));
+			auto where = vertexRelations.begin();
+			++curIdx;
+			std::advance(where, curIdx);
+			vertexRelations.emplace(where, newv, PlaneRelation::On);
+		}
+	}
+	// Create vertex vectors
+	std::array<std::vector<OpenMesh::VertexHandle>, 2> out;
+	auto filterVertices = [&vertexRelations](auto & out, auto notRelation) {
+		for (const auto & vhr : vertexRelations) {
+			if (vhr.second != notRelation) {
+				out.emplace_back(vhr.first);
+			}
+		}
+	};
+	filterVertices(out.front(), PlaneRelation::Above);
+	filterVertices(out.back(), PlaneRelation::Below);
+
+	if (out.back().size() > 2) {
+		Shape::CreatedFaces newFaces;
+		const auto oldName = mesh.property(mesh.nameFaceProperty, fh);
+		mesh.delete_face(fh);
+		const auto newf1 = newFaces.insert(mesh.add_namedFace(oldName, out.front()))->second;
+		const auto newf2 = newFaces.insert(mesh.add_namedFace(name, out.back()))->second;
+		mesh.copy_property(mesh.smoothFaceProperty, fh, newf1);
+		mesh.copy_property(mesh.smoothFaceProperty, fh, newf2);
+		fh = newf1;
+		return newFaces;
+	}
+	return {};
+}
+
 bool
 FaceController::persist(Persistence::PersistenceStore & store)
 {
 	return STORE_TYPE && STORE_MEMBER(id) && Style::persist(store) && STORE_MEMBER(type) && Mutation::persist(store)
+			&& STORE_NAME_HELPER("split", splits, Persistence::MapByMember<Splits>)
 			&& STORE_NAME_HELPER("face", faceControllers, Persistence::MapByMember<FaceControllers>);
 }
+
+bool
+FaceController::Split::persist(Persistence::PersistenceStore & store)
+{
+	return STORE_TYPE && STORE_MEMBER(id) && STORE_MEMBER(origin) && STORE_MEMBER(normal);
+}
diff --git a/assetFactory/faceController.h b/assetFactory/faceController.h
index 851292a..91860f4 100644
--- a/assetFactory/faceController.h
+++ b/assetFactory/faceController.h
@@ -10,7 +10,22 @@
 
 class FaceController : public Mutation, public Style, public Persistence::Persistable {
 public:
+	class Split : public Persistable {
+	public:
+		std::string id;
+		glm::vec3 origin, normal;
+
+	private:
+		friend Persistence::SelectionPtrBase<std::unique_ptr<Split>>;
+		bool persist(Persistence::PersistenceStore & store) override;
+		std::string
+		getId() const override
+		{
+			return {};
+		};
+	};
 	using FaceControllers = std::map<std::string, std::unique_ptr<FaceController>>;
+	using Splits = std::map<std::string, std::unique_ptr<Split>>;
 
 	void apply(ModelFactoryMesh & mesh, const Style::StyleStack & parents, const std::string & names,
 			Shape::CreatedFaces & faces) const;
@@ -18,6 +33,7 @@ public:
 	std::string id;
 	std::string type;
 	FaceControllers faceControllers;
+	Splits splits;
 
 private:
 	friend Persistence::SelectionPtrBase<std::unique_ptr<FaceController>>;
@@ -33,4 +49,6 @@ private:
 	static std::string getAdjacentFaceName(const ModelFactoryMesh & mesh,
 			const std::span<const OpenMesh::FaceHandle> ofrange, OpenMesh::FaceHandle nf);
 	Shape::CreatedFaces extrude(ModelFactoryMesh & mesh, const std::string & faceName, OpenMesh::FaceHandle) const;
+	Shape::CreatedFaces split(
+			ModelFactoryMesh & mesh, const std::string & faceName, OpenMesh::FaceHandle &, const Split &) const;
 };
diff --git a/res/brush47.xml b/res/brush47.xml
index f74cb29..20c43c8 100644
--- a/res/brush47.xml
+++ b/res/brush47.xml
@@ -70,7 +70,11 @@
             <face id="front back" colour="#e1eff3"/>
             <face id="top" type="extrude" scale="0.5,0.85,0" smooth="true" position="0,0,0.575" colour="#aeb0b0">
               <face id="top" texture="roofTopWithVents"/>
-              <face id="right left" texture="roofSideWithVents"/>
+              <face id="right left">
+                <split id="frontcorner" origin="0,7.90704,0" normal="0,1,0"/>
+                <split id="backcorner" origin="0,-7.90704,0" normal="0,-1,0"/>
+                <face id="right left" texture="roofSideWithVents"/>
+              </face>
             </face>
           </face>
         </face>