# 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!

# A few options

1- Make the big cube unrenderable by switching off the camera icon:

2- Move the big cube to a different layer that is not renderable

3- Make the shader for the BIG CUBE a holdout material (then you don't need the boolean)

4- Turn off all Ray Visibility for the object in the properties panel.

5- Use the object as mask (no need for boolean either)

• Making the object un-render-able was a quick and effective solution. Thanks! Aug 29 '15 at 16:55

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.

I can only think of a work-around, in the materials tab (on the right) set the node to mix shader.

Add a transparent shader to each one. I'm presuming this works by making it at 50% of it's transparency, then adding a second one makes the transparency 0%