Merge pull request #529 from KhronosGroup/fix/bounding_box

Fix calculation of bounding box [518]
KhronosGroup · Jan 17, 2024 · 2eceb91 · 2eceb91
2 parents 831cf2b + 1085bf6
commit 2eceb91
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Showing 2 changed files with 34 additions and 9 deletions.
diff --git a/source/gltf/accessor.js b/source/gltf/accessor.js
@@ -305,6 +305,7 @@ class gltfAccessor extends GltfObject
     }
 
     // dequantize can be used to perform the normalization from WebGL2 vertexAttribPointer explicitly
+    // https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_mesh_quantization/README.md#encoding-quantized-data
     static dequantize(typedArray, componentType)
     {
         switch (componentType)

diff --git a/source/gltf/gltf_utils.js b/source/gltf/gltf_utils.js
@@ -1,5 +1,6 @@
 import { vec3 } from 'gl-matrix';
 import { jsToGl } from './utils.js';
+import { gltfAccessor } from './accessor.js';
 
 function getSceneExtents(gltf, sceneIndex, outMin, outMax)
 {
@@ -52,19 +53,42 @@ function getSceneExtents(gltf, sceneIndex, outMin, outMax)
 
 function getExtentsFromAccessor(accessor, worldTransform, outMin, outMax)
 {
-    const boxMin = vec3.create();
     let min = jsToGl(accessor.min);
-    if (accessor.normalized){
-        vec3.normalize(min, min);
+    let max = jsToGl(accessor.max);
+
+    if (accessor.normalized) {
+        min = gltfAccessor.dequantize(min, accessor.componentType)
+        max = gltfAccessor.dequantize(max, accessor.componentType)
     }
-    vec3.transformMat4(boxMin, min, worldTransform);
 
-    const boxMax = vec3.create();
-    let max = jsToGl(accessor.max);
-    if (accessor.normalized){
-        vec3.normalize(max, max);
+    // Construct all eight corners from min and max values
+    let boxVertices = [
+        vec3.fromValues(min[0], min[1], min[2]),
+        vec3.fromValues(min[0], min[1], max[2]),
+        vec3.fromValues(min[0], max[1], min[2]),
+        vec3.fromValues(min[0], max[1], max[2]),
+
+        vec3.fromValues(max[0], min[1], min[2]),
+        vec3.fromValues(max[0], min[1], max[2]),
+        vec3.fromValues(max[0], max[1], min[2]),
+        vec3.fromValues(max[0], max[1], max[2])]
+
+
+    // Transform all bounding box vertices
+    for(let i in boxVertices) { 
+        vec3.transformMat4(boxVertices[i], boxVertices[i], worldTransform); 
+    }
+
+    // Create new (axis-aligned) bounding box out of transformed bounding box
+    const boxMin = vec3.clone(boxVertices[0]); // initialize
+    const boxMax = vec3.clone(boxVertices[0]);
+
+    for(let i in boxVertices) {
+        for (const component of [0, 1, 2]) {
+            boxMin[component] = Math.min(boxMin[component], boxVertices[i][component]);
+            boxMax[component] = Math.max(boxMax[component], boxVertices[i][component]);
+        }
     }
-    vec3.transformMat4(boxMax, max, worldTransform);
 
     const center = vec3.create();
     vec3.add(center, boxMax, boxMin);