IntroductionThe “Camera Mapping / Projection” technique is a way of projecting images (textures) directly on to geometry, without actually having to deal with the UV mapping process. This speeds up the texturing process especially when dealing with large CG Environments where huge UV maps may cause problems.
The application of the technique in the digital effects industry is directly related to the process of “Matte Painting”. This works in two ways. Projecting images on dummy geometry and simulating depth by utilizing a CG camera is the first option. Getting wireframe renders of elements through a specific camera, painting the textures on these wire frame layers and projecting them back through the same camera is the other option. In both cases the goal is to retain depth through 2D images inside 3D space; a concept know as 2.5D.
“Set Extension” is a similar technique. It is based on adding new elements to a scene. The elements might be entirely 3D renders or 2D images projected on dummy geometry created as an extension to the original scene. Any camera motion from the live-action plate will be applied to the CG camera moving inside the camera projected environment; guaranteeing proper perspective and parallax relation to the live-action backplate.
In this example from “The Ring”, various 2D matte paintings created by Christopher Stotski are camera mapped on to geometry in order to maintain a CG camera motion simulating an aerial shot.
The Case-StudyAs part of my personal research, I have created a “Camera Projected / Mapped” environment and explored some of the techniques required for this process. Since most of the educational materials covering this field are related to 3D packages like “Autodesk 3ds Max” and “Autodesk Maya”, I especially tried to focus on the ways of applying this technique inside “Side Effects Houdini”.
Here are two renders from the “Camera Projected / Mapped” environment. The example evolved around the concept of frozen time. The rest of this paper will try to illustrate the stages of this case study. Some prior Houdini knowledge is required in order to be able to understand the procedures.