Making matte/shadow-textures in instant-compositings

To complete the chrome-map tutorial, here the one to show you how to make
matte/shadow-textures in renderings.

I've posted a new thread, because you can use this also in other issues like
HDR-renderings of object into an additional photos of the HDR-environments and
more.

By the way: don't confuse the chrome-map with HDRs the one has nothing to do
with the other.

For this tutorial you'll need:
-Megapov
-A picture, where you like to put a 3d-object into.
-read this: web.496bc004fe4d566620776f0@news.povray.org

To let your 3d-object better fit into the real environment, a shadow is very
important - and in most cases its easy!

In fact, most cases means a plane: In normal environments, you have a ground and
you will put something on it. What you need is a plane that is more or less
opaque in-, and invisible outside of the shadows.

The first step is, to fit the plane, or other objects, to the
background-picture. this is the most difficult part. Sometimes you need to
adjust your lens-angle to.

When this is done, do this:

plane {y,0  // adjust plane first
hollow on
pigment {
projection {
object {your_object} // this pattern projects your object onto the plane
point <-20,40,15> // point of the light_source
//normal on  // use this to get an occlusion-effect                        //
instead of a normal shadow
blur .1,64  // this blurs your shadow (amount,samples)
}
color_map {
[0 color rgbt 1] // this is outside of the shadow (invisible)
[1 color rgbt <0,0,0,0.5>] // experiment with the last value:
}}}      // 1=invisible 0=black

If you have more than one object, define them as a union{..} and take them for
the projection{object{...}} keyword.

To finalize your rendering, focus the camera somewhere between your object and
the camera-plane that contains the background-image. Use small values for the
aperture keyword.

With this trick, you cam adjust the sharpness between you object and the photo.

Sharp objects often looking very artificial.

Have fun

Holger

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