From 23373e85da6f2543c93ac3b79ec90c842e0537c7 Mon Sep 17 00:00:00 2001
From: codereader <greebo@angua.at>
Date: Wed, 7 Oct 2020 20:25:15 +0200
Subject: [PATCH] #5326: Export a .mtl material library file next to the .obj
 file

---
 .../model/export/WavefrontExporter.cpp        | 100 ++++++++++++++++--
 radiantcore/model/export/WavefrontExporter.h  |   3 +-
 2 files changed, 95 insertions(+), 8 deletions(-)

diff --git a/radiantcore/model/export/WavefrontExporter.cpp b/radiantcore/model/export/WavefrontExporter.cpp
index 4444c74de1..b30c85a894 100644
--- a/radiantcore/model/export/WavefrontExporter.cpp
+++ b/radiantcore/model/export/WavefrontExporter.cpp
@@ -7,6 +7,11 @@
 namespace model
 {
 
+namespace
+{
+    const char* const EXPORT_COMMENT_HEADER = "# Generated by DarkRadiant's OBJ file exporter";
+}
+
 IModelExporterPtr WavefrontExporter::clone()
 {
 	return std::make_shared<WavefrontExporter>();
@@ -26,29 +31,45 @@ const std::string& WavefrontExporter::getExtension() const
 
 void WavefrontExporter::exportToPath(const std::string& outputPath, const std::string& filename)
 {
-    // Open the stream to the output file
-    stream::ExportStream output(outputPath, filename, stream::ExportStream::Mode::Text);
+    // Open the stream to the .obj file (and the .mtl file)
+    stream::ExportStream objFile(outputPath, filename, stream::ExportStream::Mode::Text);
 
-    exportToStream(output.getStream());
+    fs::path mtlFilename(filename);
+    mtlFilename.replace_extension(".mtl");
+    stream::ExportStream mtlFile(outputPath, mtlFilename.string(), stream::ExportStream::Mode::Text);
 
-    output.close();
+    writeObjFile(objFile.getStream(), mtlFilename.string());
+    writeMaterialLib(mtlFile.getStream());
+
+    objFile.close();
+    mtlFile.close();
 }
 
-void WavefrontExporter::exportToStream(std::ostream& stream)
+void WavefrontExporter::writeObjFile(std::ostream& stream, const std::string& mtlFilename)
 {
+    // Write export comment
+    stream << EXPORT_COMMENT_HEADER << std::endl;
+
+    // Write mtllib file
+    stream << "mtllib " << mtlFilename << std::endl;
+    stream << std::endl;
+
 	// Count exported vertices. Exported indices are 1-based though.
 	std::size_t vertexCount = 0;
 
 	// Each surface is exported as group. 
-	for (const Surfaces::value_type& pair : _surfaces)
+	for (const auto& pair : _surfaces)
 	{
 		const Surface& surface = pair.second;
 
 		// Base index for vertices, added to the surface indices
 		std::size_t vertBaseIndex = vertexCount;
 
-		// Since we don't write .mtl files store at least the material into the group name
+		// Store the material into the group name
 		stream << "g " << surface.materialName << std::endl;
+
+        // Reference the material we're going to export to the .mtl file
+        stream << "usemtl " << surface.materialName << std::endl;
 		stream << std::endl;
 
 		// Temporary buffers for vertices, texcoords and polys
@@ -89,4 +110,69 @@ void WavefrontExporter::exportToStream(std::ostream& stream)
 	}
 }
 
+void WavefrontExporter::writeMaterialLib(std::ostream& stream)
+{
+    // Write export comment
+    stream << EXPORT_COMMENT_HEADER << std::endl;
+
+    for (const auto& pair : _surfaces)
+    {
+        const Surface& surface = pair.second;
+
+        auto material = GlobalMaterialManager().getMaterialForName(surface.materialName);
+
+        const auto& layers = material->getAllLayers();
+
+        stream << "newmtl " << surface.materialName << std::endl;
+        stream << "Ns 0.0" << std::endl; // shininess 
+        stream << "Ka 1.000000 1.000000 1.000000" << std::endl; // ambient colour
+        stream << "Kd 1.000000 1.000000 1.000000" << std::endl; // diffuse colour
+        stream << "Ks 1.000000 1.000000 1.000000" << std::endl; // specular colour
+        stream << "d 1.000000" << std::endl; // (not transparent at all)
+
+        std::string diffuseFilename;
+        std::string specularFilename;
+        std::string bumpFilename;
+
+        for (const auto& layer : layers)
+        {
+            if (layer->getType() == ShaderLayer::DIFFUSE)
+            {
+                diffuseFilename = layer->getMapImageFilename();
+            }
+            else if (layer->getType() == ShaderLayer::BUMP)
+            {
+                bumpFilename = layer->getMapImageFilename();
+            }
+            else if (layer->getType() == ShaderLayer::SPECULAR)
+            {
+                specularFilename = layer->getMapImageFilename();
+            }
+        }
+
+        if (!diffuseFilename.empty())
+        {
+            stream << "map_Kd " << diffuseFilename << std::endl; // diffusemap
+        }
+
+        if (!bumpFilename.empty())
+        {
+            stream << "map_Kn " << bumpFilename << std::endl; // normalmap
+        }
+
+        if (!specularFilename.empty())
+        {
+            stream << "map_Ks " << specularFilename << std::endl; // specularmap
+            stream << "illum 2" << std::endl; // specular colour
+        }
+        else
+        {
+            stream << "illum 1" << std::endl; // specular colour
+        }
+
+        stream << std::endl;
+        stream << std::endl;
+    }
+}
+
 }
diff --git a/radiantcore/model/export/WavefrontExporter.h b/radiantcore/model/export/WavefrontExporter.h
index 5e2bbadd9b..c02049c35b 100644
--- a/radiantcore/model/export/WavefrontExporter.h
+++ b/radiantcore/model/export/WavefrontExporter.h
@@ -21,7 +21,8 @@ class WavefrontExporter :
 
 private:
 	// Export the model file to the given stream
-	void exportToStream(std::ostream& stream);
+	void writeObjFile(std::ostream& stream, const std::string& mtlFilename);
+	void writeMaterialLib(std::ostream& stream);
 };
 
 }