View Full Version : alpha channel bug?

06-15-2003, 09:53 PM
surface opacity in alpha channels works as expected when ray trace transpanency is turned off. but if i turn ray trace transpanency on, the alpha channel is solid white.

im on a mac osx lw7.5c.

am i missing something here. has anyone else had this problem.

06-15-2003, 10:46 PM
Post a pic, hard to guess without all the details. Do you have a high reflection value for your surface? Is it semi trans??

06-15-2003, 10:55 PM
its is a object with semi trans. the alpha channel shows this when ray trace transpanency is turned off, but when ray trace transpanency is turned on, the alpha channel for this object is solid white.

06-15-2003, 11:49 PM
This may not necessarily be a bug. Depending on your settings (double sided, reflection, refraction, color filtering etc.) this could be correct. Transparencies might add up to full opaque in raytrace mode. Have you tried to crank up your transparency? Also you should check your raytrace recursions - if they are too low, LW will render wrong results.

06-16-2003, 12:02 AM
the rendered image looks the same with ray trace transpanency turned off or on. its the alpha channel that changes. i found the raytrace recursions made no diffence.

i tried rendering a box with 50% transpanency. the alpha channel for this box will be gray if i have the ray trace transpanency turned off. but if i turn the ay trace transpanency on. the box alpha channel is white.

06-16-2003, 12:13 AM
he's right, it happens with rt refraction too

switch your alpha channel to "constant value" and put in what you want, or do some compositing