View Full Version : Alpha channel and wireframe render problem

01-23-2007, 12:29 AM

I have an object wich (which?) I have rendered as wireframe. I want to
composite the object into another background and then of course I would
like to saving the alpha channel for the object, so I could cut and paste it
in photoshop for instance. I have tried saving it as tga32 and tiff32, but the
alpha channel is just empty black, so if I try a selection of the alpha channel
in psCS2 it just makes a selection around the picture frame. What am I doing
wrong here? The wireframe object is supposed to be background on some
graphics of my firms cars, so I would like to get the object as vector too.
Perhaps its possible to import the alpha channel in Illustrator CS2 or
something, but then I had to have a alpha channel in the first place which
worked :help:

01-23-2007, 12:52 AM

You have to render your front objet alone in LW and verify the folowings :

1/ Every surface of this objet must have : Surface Editor> Advanced Tab > Alpha Channel = Surface Opacity
2/ For your front objet : Object Properties > Render Tab Alpha Channel = Use Surface Setting
3/ Make a render : you must see the alpha information in the render preview window by selecting it in the top right (you can select whay you see in the render preview : alpha or image)
4/ From the render preview save your image in a 32 bit format (I use PSD 32)
5/ You shoud see the alpha channel in Photoshop and use it as usually

Hope it couls help and good luck

01-23-2007, 03:28 AM
Hi Steph, thanks for the reply. I have got your settings, but it didn't help.
Well, if I render with realistic shading I see the alpha channel, but not with
wireframe. I think I overcome the problem though by using white as wireframe
color with black background. Then it should be just like an alpha channel right!?! :D

01-23-2007, 05:40 AM
Excuse me, I think I had a bad understanding of your problem.
I thought you want an alpha channel on another objet than your wireframe.

But I have yet another solution:
you can made your wireframe objet made of two points poly and render it a normal way (be careful, you have to use the classic camera to render 2 points poly, the persp cam don't see them)
To make this :
1/ Select all points of your object in Modeler
2/ Extend these new points (shortcut e) far from the original and delete them
3/ In doing that, you have created 2 points poly on your original model that you can isolate in the stasitic windows (shortcut w)
4/ Use this two points poly to render in realistic mode with a classic camera in layout

In the following example, each layer of ball.lwo correspond to a step

The avantage is that you can color your wireframe, specularity, have an alpha map, using it an a normal objet. You can see influence of light in the folowing exemple.

You can even change the thickness of lines in Objet properties > Render > Particles-lines

Hope you understand cause my english is not really perfect.Goood luck.

01-23-2007, 05:45 AM
or you can make an alpha channel from your picture in photoshop..