Select one object. > Modify panel > Modifier List > Object-Space Modifiers > Camera Map
Select one object. > Modifiers menu > UV Coordinates > Camera Map
The Camera Map modifier (object-space version) assigns planar mapping coordinates based on the current frame and the camera specified in the Camera Map modifier. This differs from the Camera Map (WSM) modifier that updates the object's mapping coordinates on every frame.
In the Procedures section (below), you'll be blending an object into the background using the Camera Map modifier. If the background uses the same image as the object's texture map, then the object blends with the background at the frame where the modifier is applied and a camera is specified. The object becomes visible if either the camera or object moves. In order to make the illusion work, you must assign the same map to the background that you assign to the object.
Because the accuracy of mapped objects depends partly on the complexity of the mesh, the "blend to background" effect works best when applied to an object with a relatively high density of triangular faces. The necessary density also depends on the distance of the object from the camera.
A simple box might look fine when it occupies only a small portion of the background, but up close the mapping will look distorted without adequate tessellation. Some experimentation is required to get an ideal mapping and still minimize the complexity of the geometry. (In general, for a box object that's filling a quarter of the screen, a tessellation of 4x4x4 works well.)
Note: When using the Camera Map modifier, apply the modifier to a single object at a time. If it's applied to a selection set, only the first item in the selection will be mapped properly.
Use Camera Map (WSM) if you want to move the camera and maintain the match to the background.
The following steps show how to apply the Camera Map modifier, and how to set up your scene.
To apply the Camera Map modifier:
Create a scene with a camera and one or more objects. Make sure the object you want to map is visible in the Camera viewport.
Select the object, and apply the Camera Map modifier.
Use the Object-Space Camera Map modifier, the one without the asterisk.
If you have animation in the scene, move to the frame where you want the object map to match the background. For example, if the camera is animated, the mapping will match only at this frame.
On the Camera Mapping rollout, click Pick Camera, and then select the camera used for the rendered view.
To assign a background image to the Camera viewport:
Note: This procedure is not necessary for successful rendering, but if you want to see the effect in a viewport, follow these steps.
On the Viewport Background dialog that displays, click the Files button, and choose the same bitmap that you plan to apply as a background for the rendered scene, and as a diffuse map on the object.
Turn on Display Background, and click OK.
The dialog is dismissed and the map is displayed in the viewport.
To assign a mapped material to the object:
In the Material Editor, create a standard material to whose Diffuse component you've assigned the same bitmap as you assigned to the background.
At the Diffuse Map level of the material, turn on the Show Map In Viewport button.
Select the object, and click Assign Material To Selection.
The map on the object in the viewport matches the viewport background, but the shading makes the object visible. To make the object truly invisible, go to the next step.
At the top level of the object's material, set Specular Level and Glossiness to 0. Turn off Self Illumination Color, and set Self Illumination to 100.
To assign the background to the rendered background:
In the Environment dialog that displays, click the button below "Environment Map" to open the Material/Map Browser.
Turn off Root Only, find the map in the list window, highlight it, and choose OK.
In the Exposure Control rollout on the Environment dialog, make sure the exposure is set to <no exposure control> or the turn off the Active switch.
If this is not done, you will be able to see the object in the rendering.
The mapped object is camouflaged against the background in the rendered scene.