Export shaded view w/ Alpha channel?

[patricks]

I'm going through some preliminary design on a building addition, and I've created several 3D views set up to match several photos of the existing building/site. I've just been exporting JPEG images of the shaded views, as I don't really need to do actual renderings just yet. However I can't seem to get the view to export with an alpha channel so that the white space around the building model is transparent. Is this possible in a shaded view?

[tomnewsom]

The answer is no. JPG can't do alpha anyway, but the formats that can (PNG and TIF) don't export this information. You should be using PNG or TIFF anyway, as JPG is not good at preserving sharp detail in line/shaded images.

[patricks]

Yeah I tried exporting a shaded view as a PNG file, but the background was solid white instead of transparent. That makes it very tedious trying to erase all the white around the building when placing it in a photo in Photoshop.

[aaronrumple]

Here's a trick:

Make a red (or whatever color you like) image. Place the image on a sheet as background. Place the rendering on a sheet. The building will mask the image. Print the sheet. You'll now have a nice color you can select and use to create a alpha channel in PS.

Or skip the red image and place a sky or other background. You'll then have a pretty complete rendering coming out of Revit. This is the technique II used on these images:

http://www.kai-db.com/images/portfolio/design/HigherEducation/Large/Harrison/HarrisonEdCenter.htm

[tomnewsom]

Here's a trick:

Make a red (or whatever color you like) image. Place the image on a sheet as background. Place the rendering on a sheet. The building will mask the image. Print the sheet. You'll now have a nice color you can select and use to create a alpha channel in PS.

Or skip the red image and place a sky or other background. You'll then have a pretty complete rendering coming out of Revit. This is the technique II used on these images:

http://www.kai-db.com/images/portfolio/design/HigherEducation/Large/Harrison/HarrisonEdCenter.htm
Renders saved as TIF have transparency, or at least they did with accurender - I have no idea if the same works in mental ray.

[ws]

Renders saved as .png will have transparency around the building where in a .jpg there would be 'sky' or views looking out from inside will have transparent windows - either way you can slip an image behind in a Photoshop layer and resize to look right.

I can't see an easy way to do something similar with shaded views but I didn't actually realise you could export shaded views anyway, thanks.

While on the subject someone mentioned in one of the forums here that Piranesi will now accept .fbx export out of Revit which is an interesting option.

[aaronrumple]

I can't see an easy way to do something similar with shaded views but I didn't actually realise you could export shaded views anyway, thanks.

Easy as noted in tip above. Any view 2D or 3D, wireframe, hidden line or shaded can be exported. I perfer to print to PDF rather than export as it gives me a little more control of image/sheet composition inside Revit.

[patricks]

I can't just do it from a sheet in Revit. I have to do it in Photoshop because there are existing elements that will be in front of the building model, so I have to use 3 or more layers in Photoshop to get it to look right. Having the building model image come in with nothing around it already saves alot of time.

I've resorted to just doing rendered images instead of shaded. They only take a minute to render a 3000 pixel image at Medium setting, and I can just export that as a PNG and bring it into Photoshop, while it takes me several minutes to erase the white from around the shaded building image.

[jeffh]

...I didn't actually realise you could export shaded views anyway, thanks.


You can actually export any view to an image. I have done this exporting a hidden line view of a perspective and then doing a render of the same view. Then bring both images into an image editor so I can produce a fade effect between the linework image and the rendered image.

[Phil Read]

Here's another idea (which I'll admit is a horrible hack).

Wrap the project in a Really Tall Wall (TM). Call it "Sky Wall" or something to filter it from schedules. Make this wall color bright green. Now you can export shaded views and select the exported color (background) in PS.

-Phil

[patricks]

Here's another idea (which I'll admit is a horrible hack).

Wrap the project in a Really Tall Wall (TM). Call it "Sky Wall" or something to filter it from schedules. Make this wall color bright green. Now you can export shaded views and select the exported color (background) in PS.

-Phil

pseudo-green screen heh... I may give that a try on other projects. I'm almost done with my rendered views on this one now.

I would have preferred the shaded views, though, so I wouldn't have to spend as much time finding actual rendered materials. I would rather have a more diagrammatic color surface showing, since it's early in the project.

[patricks]

I tried the "green screen" method first with the normal JPEG (Medium) image setting, and then used the Magic Wand tool in Photoshop to select all the green pixels so I could delete them. This made the selection path around the building extremely jagged, due to JPEG compression artifacts around the building that weren't exactly the same color as the green background.

So I tried again exporting to a TIFF file and that worked great. File size wasn't too bad, either. Bitmap also worked, but the resulting image was over 17MB. The TIFF file was only 800 KB and the selection path followed the building outline perfectly.

*edit* I feel dumb now :p I could have just used the Magic Wand tool on the white background after exporting a shaded view to TIFF. No extra "green screen" walls or anything like that needed. Oh well, learn a new tool every day. :)

[truevis]

You can put an image on a sheet then place the perspective view on top of it. Move your view's camera around to match the position of the real camera.