fix: vec3OrthoNormalize, handle an edge case

0b5vr · Jan 31, 2022 · feaf0af · feaf0af
1 parent bf4c45a
commit feaf0af
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Showing 2 changed files with 28 additions and 4 deletions.
diff --git a/src/math/vec3/tests/vec3OrthoNormalize.test.ts b/src/math/vec3/tests/vec3OrthoNormalize.test.ts
@@ -1,5 +1,6 @@
 import '../../../tests/matchers/toBeCloseToArray';
 import { vec3OrthoNormalize } from '../vec3OrthoNormalize';
+import { vecLengthSq } from '../../vec/vecLengthSq';
 import type { RawVector3 } from '../RawVector3';
 
 describe( 'vec3OrthoNormalize', () => {
@@ -32,4 +33,12 @@ describe( 'vec3OrthoNormalize', () => {
     expect( subject.tangent ).toBeCloseToArray( [ 0.707, 0.707, 0.0 ] );
     expect( subject.binormal ).toBeCloseToArray( [ -0.707, 0.707, 0.0 ] );
   } );
+
+  it( 'does its job even when normal and tangent is same', () => {
+    const normal: RawVector3 = [ 0.0, 0.0, -1.0 ];
+    const subject = vec3OrthoNormalize( normal, normal );
+
+    expect( subject.normal ).toBeCloseToArray( [ 0.0, 0.0, -1.0 ] );
+    expect( vecLengthSq( subject.tangent ) ).toBeCloseTo( 1.0 );
+  } );
 } );
diff --git a/src/math/vec3/vec3OrthoNormalize.ts b/src/math/vec3/vec3OrthoNormalize.ts
@@ -1,5 +1,9 @@
-import { vec3Cross } from '.';
-import { vecDot, vecNeg, vecNormalize, vecScale, vecSub } from '..';
+import { vec3Cross } from './vec3Cross';
+import { vecDot } from '../vec/vecDot';
+import { vecNeg } from '../vec/vecNeg';
+import { vecNormalize } from '../vec/vecNormalize';
+import { vecScale } from '../vec/vecScale';
+import { vecSub } from '../vec/vecSub';
 import type { RawVector3 } from './RawVector3';
 
 /**
@@ -16,9 +20,20 @@ export function vec3OrthoNormalize(
     binormal: RawVector3,
   } {
   const n = vecNormalize( normal );
+  let t = vecNormalize( tangent );
 
-  const dotNT = vecDot( n, tangent );
-  const t = vecNormalize( vecSub( tangent, vecScale( n, dotNT ) ) );
+  let dotNT = vecDot( n, t );
+
+  if ( dotNT === 1.0 ) {
+    if ( Math.abs( n[ 1 ] ) > Math.abs( n[ 2 ] ) ) {
+      t = [ 0.0, 0.0, 1.0 ];
+    } else {
+      t = [ 0.0, 1.0, 0.0 ];
+    }
+    dotNT = vecDot( n, t );
+  }
+
+  t = vecNormalize( vecSub( t, vecScale( n, dotNT ) ) );
 
   let b = vec3Cross( t, n );
   if ( binormal && vecDot( b, binormal ) < 0.0 ) {