Making an Invisible Material in the Cycles render engine I'm a newcomer to Blender and have created a scene in which I want to animate the disappearance of an object. I don't know if this is the 'right' way to do this, but I managed to get the desired effect by having a big block move over the object to be disappeared, and I added a boolean Difference modifier to the object to be disappeared.

This gets me the effect that I want, but I haven't been able to get my big block 100% transparent. It's almost, but not quite, entirely unlike a solid object, but it still casts a shadow and appears to have other visual effects on the animation that I don't fully understand.

Can anyone hand-hold me through creating an absolutely invisible material for my big block, or teach me the 'correct' way to accomplish my goals?

Thanks!
If you want the object to disappear gradually I would do it with the material.  To make it disappear from top to bottom/side to side etc. (like a box covering it up as you described) I would se this node setup for it's material.



You can then animate the value on the greater than node (the one in yellow) from 1 to 0 to make the object disappear from top to bottom.  If you want left to right use the X value from the separate XYZ node.



This works because taking the X, Y, or Z component of the generated texture coordinates gives a gradient from 0 to 1 from left to right, front to back, or back to front respectively.  The output of this, sent through a greater than node to chop it off at a certain point, is used to drive a mix shader mixing the normal material (in this case the diffuse shader) with a transparent shader.  When you animate the value of the greater than node you are animating the cutoff point.