3dtiles: EXT_texture_webpを利用する (#604)

<!-- Close or Related Issues -->
Close #597

### Description（変更内容）
<!-- Please describe the motivation behind this PR and the changes it introduces. -->
<!-- 何のために、どのような変更をしますか？ -->

- テクスチャにwebpが含まれている場合、EXT_texture_webpの拡張機能を利用するように変更

### Notes（連絡事項）
<!-- If manual testing is required, please describe the procedure. -->
<!-- 手動の動作確認が必要なら、手順を簡単に伝えてください。その他連絡事項など。 -->

- None / なし

nusamai-gltf/nusamai-gltf-json/src/models/extensions/mod.rs

@@ -1,2 +1,3 @@
 pub mod gltf;
 pub mod mesh;
+pub mod texture;

nusamai-gltf/nusamai-gltf-json/src/models/extensions/texture/mod.rs

@@ -0,0 +1,19 @@
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use std::collections::HashMap;
+
+#[derive(Serialize, Deserialize, Debug, Default, PartialEq)]
+pub struct ExtTextureWebp {
+    pub source: u32,
+}
+
+#[derive(Serialize, Deserialize, Debug, Default, PartialEq)]
+
+pub struct TextureExtensions {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(rename = "EXT_texture_webp")]
+    pub ext_texture_webp: Option<ExtTextureWebp>,
+
+    #[serde(flatten)]
+    pub others: HashMap<String, Value>,
+}

nusamai-gltf/nusamai-gltf-json/src/models/image.rs

@@ -10,6 +10,8 @@ pub enum MimeType {
     ImageJpeg,
     #[serde(rename = "image/png")]
     ImagePng,
+    #[serde(rename = "image/webp")]
+    ImageWebp,
 }
 
 /// Image data used to create a texture. Image MAY be referenced by an URI (or IRI) or a buffer view index.

nusamai-gltf/nusamai-gltf-json/src/models/texture.rs

@@ -1,5 +1,4 @@
-use std::collections::HashMap;
-
+use crate::extensions;
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
@@ -22,16 +21,9 @@ pub struct Texture {
 
     /// JSON object with extension-specific objects.
     #[serde(skip_serializing_if = "Option::is_none")]
-    pub extensions: Option<TextureExtensions>,
+    pub extensions: Option<extensions::texture::TextureExtensions>,
 
     /// Application-specific data.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub extras: Option<Value>,
 }
-
-#[derive(Serialize, Deserialize, Debug, Default, PartialEq)]
-#[serde(rename_all = "camelCase")]
-pub struct TextureExtensions {
-    #[serde(flatten)]
-    others: HashMap<String, Value>,
-}

nusamai/src/sink/cesiumtiles/gltf.rs

@@ -230,6 +230,28 @@ pub fn write_gltf_glb<W: Write>(
         buffers
     };
 
+    let has_webp = gltf_textures.iter().any(|texture| {
+        texture
+            .extensions
+            .as_ref()
+            .and_then(|ext| ext.ext_texture_webp.as_ref())
+            .map_or(false, |_| true)
+    });
+
+    let extensions_used = {
+        let mut extensions_used = vec![
+            "EXT_mesh_features".to_string(),
+            "EXT_structural_metadata".to_string(),
+        ];
+
+        // Add "EXT_texture_webp" extension if WebP textures are present
+        if has_webp {
+            extensions_used.push("EXT_texture_webp".to_string());
+        }
+
+        extensions_used
+    };
+
     feedback.ensure_not_canceled()?;
 
     // Build the JSON part of glTF
@@ -255,10 +277,7 @@ pub fn write_gltf_glb<W: Write>(
             ..Default::default()
         }
         .into(),
-        extensions_used: vec![
-            "EXT_mesh_features".to_string(),
-            "EXT_structural_metadata".to_string(),
-        ],
+        extensions_used,
         ..Default::default()
     };
 

nusamai/src/sink/cesiumtiles/material.rs

@@ -66,9 +66,31 @@ impl Texture {
         let (image_index, _) = images.insert_full(Image {
             uri: self.uri.clone(),
         });
-        nusamai_gltf_json::Texture {
-            source: Some(image_index as u32),
-            ..Default::default()
+
+        // Get the file extension
+        let extension = Path::new(self.uri.path())
+            .extension()
+            .and_then(|ext| ext.to_str())
+            .map(|ext| ext.to_lowercase());
+
+        if extension == Some("webp".to_string()) {
+            nusamai_gltf_json::Texture {
+                extensions: Some(nusamai_gltf_json::extensions::texture::TextureExtensions {
+                    ext_texture_webp: Some(
+                        nusamai_gltf_json::extensions::texture::ExtTextureWebp {
+                            source: image_index as u32,
+                        },
+                    ),
+                    ..Default::default()
+                }),
+                source: Some(image_index as u32),
+                ..Default::default()
+            }
+        } else {
+            nusamai_gltf_json::Texture {
+                source: Some(image_index as u32),
+                ..Default::default()
+            }
         }
     }
 }
@@ -134,6 +156,10 @@ fn load_image(feedback: &Feedback, path: &Path) -> std::io::Result<(Vec<u8>, Mim
                 feedback.info(format!("Embedding a jpeg as is: {:?}", path));
                 Ok((std::fs::read(path)?, MimeType::ImageJpeg))
             }
+            Some("webp") => {
+                feedback.info(format!("Embedding a webp as is: {:?}", path));
+                Ok((std::fs::read(path)?, MimeType::ImageWebp))
+            }
             _ => {
                 let err = format!("Unsupported image format: {:?}", path);
                 log::error!("{}", err);