I’m trying to do a composite rendering using the pytsai script. Camera match worked quite good and in camera view everything is properly arranged to my backgroundimage, but when I render the image, the background image disapears. I’ve looked through the manual but didn’t find a easy way to get it rendered. It seems this can be achieved using nodes, but I’m quite new to blender and got no clue how to use them.
Another question is how an objects shadow can be rendered on a plane, that itself should be invisible. ( I matched a photo of my desk to a plane and now I want to add some objects. the plane should become invisible and the shadows casted on the photo)
I hope I made my intention clear and someone can help me, otherwise I could add some screenshots
Screenshots always help, but I will give it a try. When you say background image, if you are refering to an image added to the 3d scene via view…background image, that wont render. The background image is used mostly as a modeling reference.
To add an image to a render, you would use an alpha over node in compositing.
Objects will cast a shadow as long as the light is set for ray tracing, “Ray” is turned on in rendering options, and (most often missed - by me) the object that is to receive the shadow must usa a material with “TraShad” turned on.
you helped me a lot, thx! using nodes isnt that complicated as i thought also my problem with shadows is partly solved. I took some some screenshots because now its getting a bit complicated for me to explain www.valentinsteiff.de/blender/screenshot.jpg
Here you can see the material for my desk. I’m using 2 lamps. lamp1 to cast a shadow and illuminate the scene (Ray Shadow = ON ; OnlyShadow = OFF), lamp2 just for illumination (Ray Shadow = OFF ; OnlyShadow = OFF) http://www.valentinsteiff.de/blender/render1.png this is what it looks like, I get a very dark shadow. Now I switched Ray Shadow = ON for lamp2, shadow gets brighter, but now I have 2 of them http://www.valentinsteiff.de/blender/render2.png which doesnt look that realistic how can I solve that problem? another thing is that my desk is quite shiny. how can i add diffuse reflections to my desk material?
With respect to shadows, withought some form of global illumination, the shadows will be very dark. Some people use Ambient Occlusion for global illumination, others use hemi lamps dupliverted to a half sphere.
See this thread: http://blenderartists.org/forum/showthread.php?t=79502
I have posted 3 sets of pics to this wip thread. Take a look at the last 2. In one, I have added a lantern to the column, and rendered it with a single lamp (sun). In the last, I have added some faked global illumination by:
Adding an icosphere
Deleting half of the verts
Reverse the normals of the verts (inward)
Add a hemi lamp
Parent the hemi lamp to the half sphere
Turn dupliverts on for the half sphere (F7 “Anim settings” panel)
This will duplicate the hemi lamp at every vertice of the sphere, aligned with the surface normals. Now you have the equivalent of 26 lamps, the settings for which can all be controlled by changing the settings for the original lamp. Positioning can be controlled by scalling and moving the half sphere. In my case, I changed the energy setting for the original lamp to .08.
also my problem with shadows is partly solved. I took some some screenshots because now its getting a bit complicated for me to explain 
