The painting process was great because we had our full HD 3D base render, and it was all about coloring and playing around with textures and developing, at this early stage, the final look of the environment.
We figure out during this stage that we had to divide the environment into different paintings. For example, we had a BG paint, then the mid front elements, then the front elements and a second layer of front elements. Even the volumetric lights were painted preserving the alpha channel. This gave us different paintings to cover the different depths of elements around the scene, so that when the camera panned near a front element you could see the full painting of the elements behind.
But despite the fact that the theory of dividing the paint according to the distribution of elements on the set was working pretty well, we did run into a couple of problems.
One of them was about how the volumetric light reacted to the scene when it was projected. This meant that when we painted on a layer in Photoshop with an overall blending mode, it was working great. But when we applied that same volumetric on a 3D plane and rendered it, the blending mode was no more and the volumetric wasn't blending with the background the same way it did in Photoshop.
We solved that problem by painting the volumetric on the background paint and keeping the volumetric layer with a minimum opacity, and it worked pretty nicely (Fig.06 & Fig.07) (Mov.02).
For this stage we used the Camera Map Per Pixel material that comes with the latest 3ds Max versions, and this is a really easy process. You just need to choose the camera you are going to use to project the image and then under the Texture option you pick the image you want to project over the mesh (Fig.08 & Fig.09).
Choosing The 'Locked' Camera
There's something very important about the workflow when you're working with projection. At the very beginning of the process you need to decide the exact camera position in your scene for the camera that is going to be used for the projection. We named it "locked" camera, because once you choose the position you must never change it. Remember that this "locked" camera is where you are going to get your 3D base render from for the painting process.
Deciding The Camera Movement
So once you have the "locked" camera, you can clone it and rename it ("animated" camera). Then you go to the half of your timeline and create a key for the "animated" camera at the exact same position that the "locked" camera is.
Now you can play around by adding a starting key at frame 0 and an ending key at the last frame of your timeline. You are going to make a camera movement you like, where at the exact halfway point of the motion you are going to match the "locked" camera position. This is going to help you understand how much of the original paint - the one you did over your 3D base render - you are going to need to extend in order to cover the new mesh that appears when moving the camera (Fig.10 & Fig.11).