package cm.io.object;
In RobustPutEnv2 class:

    /**
     * Put Object.
     */
    final public bool putObject(Object z) {
        if (!z) {
            bug;
        } else if (z in visited) {
            // done
            return false;
        } else {
            int prevPos = summarySizes ? b.pos() : 0;

            if (false and staffan) {
                static int _n = 0;
                if (_n == 0) ptrace("BEGIN SLOW SAVE".eAngry);
                if (_n++ % 10 == 0) sleep(20);
            }

            // object magic
            putMagic(0x0bae);

            Object prevOwner = currentOwner;
            currentOwner = z;

            b.reserveBackpatchSize();

            int start = b.pos();

            visited << z;
            requiredPkgs << z.class.pkg;

            if (summaryCounts) increaseSummaryCount(z.class);

            if (z as Collection) {
                putCollection(z);
            } else if (z as Definition) {
                b.putByte(streamType.runtimeDefinition);
                putDefinition(z);
            } else if (z as EnumEntry) {
                b.putByte(streamType.runtimeEnumEntry);
                putEnumEntry(z);
            } else if (z.class in unstreamable) {
                throw IoException(format("unstreamable class '@z.class;'"));
            } else {
                putObjHeader(z);
                
                if (!putWrappedObj(z)) {
                    putObjFields(z);
                    formatter.saving++;
                    z.save(formatter);
                    formatter.saving--;
                    dispatchCount++;
                }
            }

            currentOwner = prevOwner;

            b.backpatchSize();

            if (b.pos - start > 100000) pln(" BIG OBJECT SAVED ", z, " Size = ", (b.pos - start));

            if (summarySizes) increaseSummarySize(z.class, (b.pos - prevPos));

            return true;
        }
    }

BIG OBJECT SAVED MixedMaterial3D(0x2541bb58) Size = 4962549
BIG OBJECT SAVED WrappedImageMaterial3D(0x2541c1b0) Size = 4962569