Add snippet for SpatialGltfModel (#889)

Author: amyZepp

xr/src/main/java/com/example/xr/compose/SpatialGltfModel.kt

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.xr.compose
+
+import android.util.Log
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.xr.compose.platform.LocalSession
+import androidx.xr.compose.subspace.SpatialGltfModel
+import androidx.xr.compose.subspace.SpatialGltfModelSource
+import androidx.xr.compose.subspace.layout.SubspaceModifier
+import androidx.xr.compose.subspace.rememberSpatialGltfModelState
+import androidx.xr.runtime.math.Pose
+import androidx.xr.runtime.math.Quaternion
+import androidx.xr.runtime.math.Vector4
+import androidx.xr.scenecore.AlphaMode
+import androidx.xr.scenecore.KhronosPbrMaterial
+import androidx.xr.scenecore.Texture
+import java.nio.file.Paths
+import kotlin.io.path.Path
+
+@Composable
+fun SpatialGltfModelExample(){
+    val xrSession = checkNotNull(LocalSession.current)
+    val degrees = 1f
+
+    // [START androidxr_compose_SpatialGltfModelState]
+    val modelState = rememberSpatialGltfModelState(
+        source = SpatialGltfModelSource.fromPath(
+            Paths.get("models/bugdroid_animated_wave.glb")
+        )
+    )
+    // [END androidxr_compose_SpatialGltfModelState]
+
+    // [START androidxr_compose_SpatialGltfModelMaterial]
+    // Retrieve the list of nodes (individual components/meshes) defined within the glTF model.
+    val entityNodes = modelState.nodes
+
+    // Find a specific node by name to apply modifications, such as material overrides.
+    val node = entityNodes.find { it.name == "node_name" }
+
+    // Maintain a reference to the custom material to avoid re-creating it on every recomposition.
+    var pbrMaterial by remember { mutableStateOf<KhronosPbrMaterial?>(null) }
+
+    // Create and apply the custom material once the session is ready and the target node is available.
+    LaunchedEffect(node) {
+        val material = pbrMaterial ?: KhronosPbrMaterial.create(
+            session = xrSession,
+            alphaMode = AlphaMode.OPAQUE
+        ).also {
+            pbrMaterial = it
+            // Load a texture
+            val texture = Texture.create(
+                session = xrSession,
+                path = Path("textures/texture_name.png")
+            )
+
+            // Configure occlusion to define how the material surface handles ambient lighting.
+            it.setOcclusionTexture(
+                texture = texture,
+                strength = 1.0f
+            )
+
+            // Apply a base color factor (RGBA) to tint the model.
+            it.setBaseColorFactor(
+                Vector4(
+                    x = 0.5f,
+                    y = 0.5f,
+                    z = 1.0f,
+                    w = 1.0f
+                )
+            )
+        }
+
+        // Apply the custom PBR material to the specific node, overriding its original glTF material.
+        node?.setMaterialOverride(
+            material = material
+        )
+    }
+    // [END androidxr_compose_SpatialGltfModelMaterial]
+
+    // [START androidxr_compose_SpatialGltfModelIntrospection]
+    val arrows = modelState.nodes.find {
+        it.name == "Arrows"
+    }
+
+    LaunchedEffect(arrows, degrees) {
+        val rotation = Quaternion.fromEulerAngles(degrees, 0f, degrees)
+        arrows?.localPose =
+            Pose(arrows.localPose.translation, rotation)
+    }
+    // [END androidxr_compose_SpatialGltfModelIntrospection]
+
+    // [START androidxr_compose_SpatialGltfModelLoad]
+    // Render the 3D model into the spatial subspace.
+    SpatialGltfModel(state = modelState, modifier = SubspaceModifier)
+    // [END androidxr_compose_SpatialGltfModelLoad]
+}