fix camera slerp() BUG

src/webgl/p5.Camera.js

@@ -1818,10 +1818,10 @@ p5.Camera = class Camera {
     const rotMat1 = cam1.cameraMatrix.createSubMatrix3x3();
 
     // get front and up vector from local-coordinate-system.
-    const front0 = rotMat0.column(2);
-    const front1 = rotMat1.column(2);
-    const up0 = rotMat0.column(1);
-    const up1 = rotMat1.column(1);
+    const front0 = rotMat0.row(2);
+    const front1 = rotMat1.row(2);
+    const up0 = rotMat0.row(1);
+    const up1 = rotMat1.row(1);
 
     // prepare new vectors.
     const newFront = new p5.Vector();

test/unit/webgl/p5.Camera.js

@@ -923,6 +923,21 @@ suite('p5.Camera', function() {
       expect(myCam.projMatrix.mat4[5])
         .to.be.closeTo(p0_5 * Math.pow(p1_5 / p0_5, 0.3), 0.00001);
     });
+    test('Preventing bugs from occurring by changes in slerp spec', function() {
+      myCam = myp5.createCamera();
+      const cam0 = myp5.createCamera();
+      const cam1 = myp5.createCamera();
+      cam0.camera(100, 763, 1073, 100, 480, 380, 0, 1, 2);
+      cam1.camera(300, 400, 700, 0, 0, 0, 2, 3, 1);
+      myCam.slerp(cam0, cam1, 0.1);
+      const expectedSlerpedMatrix = new Float32Array([
+        0.9983342289924622, 0.04771510139107704, 0.03243450075387955, 0,
+        -0.056675542145967484, 0.9162729382514954, 0.39652466773986816, 0,
+        -0.010798640549182892, -0.3977023959159851, 0.9174509048461914, 0,
+        -66.60199737548828, -260.3179016113281, -1242.9371337890625, 1
+      ]);
+      assert.deepEqual(myCam.cameraMatrix.mat4, expectedSlerpedMatrix);
+    });
   });
 
   suite('Helper Functions', function() {
@@ -1072,4 +1087,4 @@ suite('p5.Camera', function() {
       assert.deepEqual(myp5.get(0, 0), [0, 0, 0, 0]);
     });
   });
-});
+});