guard against non-invertible matrices in Camera.update

+ relative viewports and dynamic updating of them sometimes caused non-invertible matrix

src/mol-canvas3d/camera.ts

@@ -87,7 +87,12 @@ class Camera implements ICamera {
 
         if (changed) {
             Mat4.mul(this.projectionView, this.projection, this.view);
-            Mat4.invert(this.inverseProjectionView, this.projectionView);
+            if (!Mat4.tryInvert(this.inverseProjectionView, this.projectionView)) {
+                Mat4.copy(this.view, this.prevView);
+                Mat4.copy(this.projection, this.prevProjection);
+                Mat4.mul(this.projectionView, this.projection, this.view);
+                return false;
+            }
 
             Mat4.copy(this.prevView, this.view);
             Mat4.copy(this.prevProjection, this.projection);

src/mol-math/linear-algebra/3d/mat4.ts

@@ -333,7 +333,7 @@ namespace Mat4 {
         return out;
     }
 
-    export function invert(out: Mat4, a: Mat4) {
+    export function tryInvert(out: Mat4, a: Mat4) {
         const a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
             a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
             a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
@@ -356,8 +356,7 @@ namespace Mat4 {
         let det = b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;
 
         if (!det) {
-            console.warn('non-invertible matrix.', a);
-            return out;
+            return false;
         }
         det = 1.0 / det;
 
@@ -378,6 +377,13 @@ namespace Mat4 {
         out[14] = (a31 * b01 - a30 * b03 - a32 * b00) * det;
         out[15] = (a20 * b03 - a21 * b01 + a22 * b00) * det;
 
+        return true;
+    }
+
+    export function invert(out: Mat4, a: Mat4) {
+        if (!tryInvert(out, a)) {
+            console.warn('non-invertible matrix.', a);
+        }
         return out;
     }