View Full Version : How do you render part of an object transparent?

10-11-2010, 08:37 PM
I'm trying to show a solid flow arrow inside a pipe. I want to show the pipe as a sheet metal surface, but have a gradual transparency from edge to edge so the arrow shows clearly in the middle of the pipe.

I've tried weight maps and the node editor, but I'm too much a noob to get it right!

Is there an easy way?



Ryan Roye
10-11-2010, 08:47 PM
The simplest way I can think of is this:

In layout, go into the object properties and under the "Render" tab, look for "object dissolve", you can use this option to make anything transparent or invisible.

Now, I notice you said "gradual", so you'll need to click on the small "E" next to object dissolve which brings up the graph editor. Through here, you can set where in your timeline you wish to have what level of transparency with.

The graph editor is daunting at first, but its a powerful tool you'll eventually find you can't do without in Lightwave.

Another method is to do transparency via surface properties.

NOTE: Depending on your lightwave settings, you may not see transparent textures so check your Edit>Display>OpenGL options if you find nothing is happening.

10-11-2010, 09:15 PM

That's a great effect (Object Dissolve), but that dissolves the whole pipe. I may have just figured it out as I type, but what I'm after is the center of the pipe (incidence angle 0?) needs to be transparent, getting more opaque as it gets to 90. The inside of the pipe is visible (two-sided polys), so shadows from the arrows are applied inside.

Am I making any sense?

Thanks again,


10-11-2010, 09:18 PM
You could apply an incidence angle shader in the transparency layer. You just described what you need to do.

10-11-2010, 10:00 PM
Thanks for the insight. I used the Transparency Texture editor to add a gradient that goes from white at the top to clear at the bottom.

Made my night!

Thanks again all y'all.


10-12-2010, 05:48 AM
Render it separately and do it in AE or an onther composit program. It will make the renders a lot faster also.

10-12-2010, 03:53 PM
Render it separately and do it in AE or an onther composit program. It will make the renders a lot faster also.


You could also model the pipe with a hole in it. Keep the part you cut out as a separate object and dissolve just that part to show the interior.

10-21-2010, 08:54 AM
Or you could apply a UV map to the pipe and use a bitmap to control the exact location and intensity of the transparency.