Render in 32bit & Alpha Channels

[CADTutor]

Is it just me or does the 32bit render option for TIFF renders no longer save alpha channel information?

 

In AutoCAD 2006 and earlier, rendering tp 32bit TIFF resulted in a 24bit image and a saved alpha channel, which could be used as a saved selection in Photoshop. In AutoCAD 2007/08, this feature doesn't seem to work. Rendering to 32bit TIFF results in just a 24bit image and no alpha channel.

 

Anyone else have this problem?

[hazardman]

i just did a quick test render...i made a rectangle and extruded it...then i hit render and did a save as tif w/ alpha (you need to specificaly choose the 32 bit w/ alpha option)...opened in photshop and the alpha was there...

 

now i seem to remember some sort of patch w/ photoshop cs3 that resolve alpha issues but i can't remember what is was...could it be that?..

 

if you do a rendering from a previous acad version, if accessible, does the alpha work?..

 

another thought, is your object isolated enough to create an alpha, ie just black autocad space with no background and surrounding objects?..

 

anyway, short answer is that yes alphas still work--at least in my version of ACA 2k8...

 

printing to a tif file will not create alphas (just in case you might have been doing that)....

[papagyi]

Is it just me or does the 32bit render option for TIFF renders no longer save alpha channel information?

 

In AutoCAD 2006 and earlier, rendering tp 32bit TIFF resulted in a 24bit image and a saved alpha channel, which could be used as a saved selection in Photoshop. In AutoCAD 2007/08, this feature doesn't seem to work. Rendering to 32bit TIFF results in just a 24bit image and no alpha channel.

 

Anyone else have this problem?

I did for you with acad 2008.This is true? Ok or not pls reply me.

[CADTutor]

OK, I'm resurecting this thread becaue I still don't have a solution to the problem. So here's the thing. I render a drawing in AutoCAD 2004 using the 32bit TIFF option. Open in Photoshop CS3 and there is a nice Alpha Channel so I can easily select the rendered objects. Now I render the same drawing in AutoCAD 2009 using the 32bit TIFF option. I open the image in PS CS3 and... no Alpha Channel.

 

Can anyone shed any light on this - it's been a real pain for me since the renderer changed in Acad 07.

[Cadfisch]

Very strange. I’m doing it all the time – rendering in AC 2009 save as TIF with Alpha Channel then further edit it in PS CS3, exactly your combination.

[CADTutor]

Very strange. I’m doing it all the time – rendering in AC 2009 save as TIF with Alpha Channel then further edit it in PS CS3, exactly your combination.

 

Aha! So it IS just me. That must mean there is a solution. OK, so how many variables can there be? I'm using Win Vista (yes, I know...) - would you be using XP by any chance? What graphics card are you using?

 

I need to get to the bottom of this because it's costing me hours to make the selections.

[Cadfisch]

Are you sure you are using the default AC background? Once you have chosen a background even if it was true black, the Alpha channel option doesn’t work anymore.

[Cadfisch]

Sorry, I forgot to answer your other questions but the graphics chart has nothing to do with it and I doubt that the OS has. I’m using XP and the graphics is Nvidia 8600M GT.

[CADTutor]

Are you sure you are using the default AC background? Once you have chosen a background even if it was true black, the Alpha channel option doesn’t work anymore.

 

No, that's not it. If I start a new drawing, draw a box and render it to 32bit TIFF, I don't get an alpha channel.

 

Could you do the same and then attach the DWG and TIFF files here so that I can pinpoint the problem?

[Cadfisch]

Here we are, but I had to convert the TIF in PSD. TIFs are not accepted here. I checked for the alpha channel it is there!

Cube.dwg

Cube.psd

[CADTutor]

OK, I opened your PSD and the alpha channel is there. I open the DWG and render it to 32bit TIFF, open in Photoshop and - no alpha channel.

 

At least we can take Photoshop out of the equasion. It's definately an AutoCAD problem and one I've had in 07, 08 and 09. The fact that no one else has this problem must mean it is some other variable and the OS is the most obvious one.

 

Is there anyone using Acad on Vista who could check this out?

[Cadfisch]

Have you tried to save it as PNG + alpha channel? You end up with your object already selected (no background=transparent background in PS). If this doesn't work as well, you have one more evidence that some DLL(?) can not be accessed by AutoCad