On a configurable product page when a swatch/attribute is selected, the product page gallery images get overridden by the simple product image for each swatch. Or there is a extra thumbnail has been added (the image which assigned to that simple product). Which presents here as a repeated thumbnail.(screenshots attached)
And on default demo, it is like:
In magento 2, is it compulsory to add the images to all simple products? otherwise it will not show the product image when selecting the swatch or attributes.
How can i just show all the thumbnails and when some swatch been selected, its pic will shows up and its thumbnail will be highlights or have a frame effect. Like the screenshot blow: