Background and Foreground Images

On November 27, 2007, in Tutorials, by Admin

 

The first step is to switch to the Scene panel (F10). Look for the ‘Output’ Tab.
The first three icons are Folder icons with file paths associated with them. The
second line is for background images. Click the folder icon and locate the image you
wish to use for your background image. Click on the “BackBuf” button to enable your
image during rendering. 

Here is my test render after adding my background image.


Next, I’ll show you how you can add a foreground image that will make your model
appear to be within the background image. Select your camera by right clicking
it. Press ‘SHFT-S’ to bring up the ‘Snap Menu’ and select ‘Cursor to Selection’.
Press ’0′ (zero) to change your view to the current camera’s view. While looking
from your camera, press ‘Space’ – ‘Add’ – ‘Mesh’ – ‘Plane’. This will add a plane
that is lined up with your camera. Select the plane and press ‘G’ to grab it.
Press the Z key twice (Once will move the plane in the global Z direction, twice will
move the plane in the Local Z direction, which is lined up with the camera). Move
the plane away from the camera until it’s edges line up closely with the edge of
the camera’s view. You can adjust this later if it’s too close or too far away
(Pressing Z twice to move it locally).


With your plane selected, switch to the Materials panel (F5) click “Add New”.
Add a new texture material to this plane using the same background image. If you
need help with creating materials with textures you can follow my Materials Mystery
Part 2
tutorial. If you need to rotate your image on your plane, with your mouse
in the 3D view while in Object Mode press the ‘F’ key. Press ‘A’ to select all
faces and press ‘R’ to bring up the Rotate Menu. Select ‘UV Co-ordinates’ to rotate
the image on the plane. Continue these steps until the image is oriented correctly.

Using your favorite paint program, locate the dimensions of your background image
in pixels. With your plane selected in Object Mode, press ‘N’ to bring up the
properties menu. Type in the dimensions of your background image here in the lower
right hand corner for the “DimX” and “DimY” values. You may need to rescale your
image slightly to keep it in your camera view.

We’re going to use 2 images for our foreground image.
The first one will be the same
image we’re using for our background image which is already loaded.

The second one will be a hand made simple alpha mask. Using your favorite paint program, create a blank image the same dimensions as your background image. Fill it all with black.
Next, based on your test render, paint the bottom of this image white. The top edge
of the white should be approximately where you would want the grass to appear in front
of your wall as in my example. Using some fancy brushes or just blending in with a fine
point brush, rough up the edge where the black meets the white. This will simulate
the transparent parts of our image. Some of our wall will show through the sections
that are still black.

For the map input on our Alpha Mask, I left the default settings at ‘Orco’ and
‘Flat’. Under the ‘Map To’ tab, only select the ‘Alpha’ button and deselect all
other buttons in the top section.

There’s 3 things we need to do here in these sections. First, under the ‘Material’
tab, pull the ‘A’ (Alpha) slider all the way down to 0.0. Next, under the ‘Links and
Pipeline’ tab, click the ‘ZTransp’ button so it is on. Finally, under the ‘Shaders’
tab, turn the ‘Spec’ slider down to 0.0. This prevents a glare from appearing on our plane.
If all goes well, you should see a preview similar to mine. Notice only the bottom section
of grass is visible which is exactly what we want.

Here’s what we’re looking at. Our camera, our plane, our model and then our background
image. Our alpha map will make the top portion of our plane transparent so the bottom
section will appear to be grass growing up in front of our model. You may need to add
a light behind your camera so your plane appears clearly.
The end result. Our model appears to be in the picture instead of just being on
top of a back ground image.
Good Luck with your models!Scott.

 

 

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