Many artists in the 3d arts push their computers to the max and it takes several hours to complete a render. Many aren't happy with the end result and often have to cut things out of their art just to get it to render. Then you have situations where maybe you need things in the background that you have to render over and over again where you wish you didn't have to. The answer to this is to render each piece separately and to save the png's. You can then blend them any way you like and use the png's over and over saving a lot of time. You can even visit sites like Deviantart to find png's that have already been created by other artists to help you out.
More and more 2d artists are now moving to computers and they use this trick all the time.
I know what some of you may be thinking. You're a purest and you want to let your rendering software to do things for you. Then, we see you complaining you were rendering for twelve hours and something happened. The longer you render the increasing chance there will be a power outage or some other problem like you step away and the kids or a pet gets at your keyboard killing the rendering processes.
When you create art, the process varies. CG artists had to fight years to win respect as traditional artists thought that the computer was doing all the work and you just put things together. They saw it as staging your living room moving things around and taking a photo of it never thinking that this was already an accepted form of art. It's not the process used to create the art, but the vision behind it.
Blending is just another way to do this. Background items are especially easy to do this with as changing the size of a tree, the color of a car, putting figures in shadows that you've used on existing images or inside a building behind glass. A key thing to making this work though is to use standard lighting for your png renders so you can use your 2d applications (such as Photoshop) to create your lighting effects. If you do use your render engines for the lighting and shading, remember to do a render without them to save.
Blending is a time saver and it can allow you a much wider range of artistic achievement because rendering a png of a single item or a couple of items might take a few minutes where the entire scene could take hours.
It also allows you to add different artistic effects to different items and to combine various 2d and 3d processes that a traditional render may not allow
www.artstation.com/artwork/oDb5z
Some artists will even show you their creative processes using png's from simple art pieces to extremely intricate and if you don't have the items in your 3d inventory to render, you can collaborate with other artists that do.
Artist Andrey Denisov is an example of an artist that does this. He apparently goes by different usernames online or collaborates with others as you can find bits and pieces of his art in different images done by him and done by others if you do a few Google image searches.
images.wallpapersden.com/image/download/...kpJRma21lrWZlamU.jpg
images-wixmp-ed30a86b8c4ca887773594c2.wi...TIVNX6s5-5wyq51jd7e4