MeshWriter that can save both in .usd and .obj formats

openVulkanoCpp/Scene/MeshWriter.cpp

@@ -0,0 +1,153 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include "MeshWriter.hpp"
+#include "Scene/Geometry.hpp"
+#include "Scene/Vertex.hpp"
+#include <fmt/core.h>
+#include <fstream>
+#include "tinyusdz.hh"
+#include "pprinter.hh"
+#include "prim-pprint.hh"
+#include "value-pprint.hh"
+
+namespace
+{
+	uint32_t GetIndexFromGeometry(OpenVulkano::Scene::Geometry *geometry, int index)
+	{
+		uint32_t result = 0;
+
+		if (geometry->indexType == OpenVulkano::Scene::VertexIndexType::UINT16)
+		{
+			uint16_t *indices = static_cast<uint16_t *>(geometry->indices);
+			result = indices[index];
+		}
+		else if (geometry->indexType == OpenVulkano::Scene::VertexIndexType::UINT32)
+		{
+			uint32_t *indices = static_cast<uint32_t *>(geometry->indices);
+			result = indices[index];
+		}
+		else
+		{
+			throw std::runtime_error("Invalid geometry index type");
+		}
+
+		return result;
+	}
+}
+
+namespace OpenVulkano::Scene
+{
+	void MeshWriter::WriteAsOBJ(Geometry *geometry, const std::string &filePath)
+	{
+		std::ofstream file(filePath);
+
+		if (!file.is_open())
+			throw std::runtime_error("Failed to open file '" + filePath + "' for writing!");
+		
+		for (int i = 0; i < geometry->vertexCount; ++i)
+		{
+			OpenVulkano::Vertex v = geometry->vertices[i];
+			std::string line;
+
+			line = fmt::format("v {} {} {}\n", v.position.x, v.position.y, v.position.z);
+			file << line;
+
+			line = fmt::format("vn {} {} {}\n", v.normal.x, v.normal.y, v.normal.z);
+			file << line;
+
+			line = fmt::format("vt {} {}\n", v.textureCoordinates.x, v.textureCoordinates.y);
+			file << line;
+
+			// NOTE(vb): There aren't specd way to encode colors...
+		}
+
+		for (int i = 0; i < geometry->indexCount; i += 3)
+		{
+			uint32_t i0 = GetIndexFromGeometry(geometry, i + 0) + 1;
+			uint32_t i1 = GetIndexFromGeometry(geometry, i + 1) + 1;
+			uint32_t i2 = GetIndexFromGeometry(geometry, i + 2) + 1;
+			std::string line = fmt::format("f {}/{}/{} {}/{}/{} {}/{}/{}\n",
+				i0, i0, i0,
+				i1, i1, i1,
+				i2, i2, i2
+			);
+			file << line;
+		}
+
+		file.close();
+	}
+
+	void MeshWriter::WriteAsUSD(Geometry *geometry, const std::string &filePath)
+	{
+		tinyusdz::Stage stage;
+		tinyusdz::Xform xform;
+		tinyusdz::GeomMesh mesh;
+		mesh.name = "TheMesh";
+
+		std::vector<tinyusdz::value::point3f> pts(geometry->vertexCount);
+		std::vector<int> indices(geometry->indexCount);
+		tinyusdz::Attribute uvAttr;
+		std::vector<tinyusdz::value::texcoord2f> uvs(geometry->vertexCount);
+
+		for (int i = 0; i < geometry->vertexCount; ++i)
+		{
+			Vertex v = geometry->vertices[i];
+			tinyusdz::value::point3f p;
+			p.x = v.position.x;
+			p.y = v.position.y;
+			p.z = v.position.z;
+			pts[i] = p;
+			uvs[i] = { v.textureCoordinates.x, v.textureCoordinates.y };
+		}
+
+		mesh.points.set_value(pts);
+		uvAttr.set_value(uvs);
+
+		std::vector<int> counts;
+		for (int i = 0; i < geometry->indexCount / 3; ++i)
+		{
+			counts.push_back(3); // NOTE(vb): This value is kind of arbitrary, but the array must be in the mesh!
+		}
+		mesh.faceVertexCounts.set_value(counts);
+
+		for (int i = 0; i < geometry->indexCount; ++i)
+		{
+			uint32_t index = GetIndexFromGeometry(geometry, i);
+			indices[i] = index;
+		}
+		mesh.faceVertexIndices.set_value(indices);
+
+		uvAttr.metas().interpolation = tinyusdz::Interpolation::FaceVarying;
+		tinyusdz::Property uvProp(uvAttr);
+		mesh.props.emplace("primvars:UVMap", uvProp);
+
+		tinyusdz::Prim xformPrim(xform);
+		tinyusdz::Prim meshPrim(mesh);
+		std::string err;
+		if (!xformPrim.add_child(std::move(meshPrim), true, &err))
+		{
+			throw std::runtime_error("Failed to construct scene: " + err);
+		}
+		if (!stage.add_root_prim(std::move(xformPrim)))
+		{
+			throw std::runtime_error("Failed to add prim to stage root: " + stage.get_error());
+		}
+		stage.metas().defaultPrim = tinyusdz::value::token(xformPrim.element_name());
+		stage.metas().comment = "Generated by OpenVulkanoCpp";
+		if (!stage.commit())
+		{
+			throw std::runtime_error("Failed to commit stage: " + stage.get_error());
+		}
+
+		std::ofstream file(filePath);
+		if (!file.is_open())
+			throw std::runtime_error("Failed to open file '" + filePath + "' for writing!");
+		std::string scene = to_string(stage);
+		file << scene << "\n";
+		file.close();
+	}
+}

openVulkanoCpp/Scene/MeshWriter.hpp

@@ -0,0 +1,20 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <string>
+
+namespace OpenVulkano::Scene
+{
+	class Geometry;
+	class MeshWriter
+	{
+	public:
+		static void WriteAsOBJ(Geometry *geometry, const std::string &filePath);
+		static void WriteAsUSD(Geometry *geometry, const std::string &filePath);
+	};
+}