Creating an Alpha mask of your model for 2D Graphic export.

[DavidMac]

This tutorial is a partner to "Exporting 2D graphics with NO size limits". elsewhere in this forum http://forums.sketchucation.com/viewtopic.php?f=18&t=26527

In a recent thread on exporting 2D images I heard that exporting transparency for a 2D graphic is apparently a luxury available only to Mac users.

Here is a work around for non Mac users which allows you to export an Alpha channel of just your model using SU's 2D export. It is a bit clunky, especially if your model is very complex, but it produces very accurate masking and will certainly do until something better comes along.

I am very much the amateur in SU. (I am really a Photographer/Photoshopper who uses SU to produce elements to use in Photoshop for creating photo realistic illusions.) So it is very likely that the more experienced among you will be able to fine tune this method further.

That being said, although, like all instructions, it looks very long and tedious, to do the actions is really quite quick and simple.

1. First position your model for export.

2. In the Scenes dialogue uncheck everything except Camera Location and save the current camera position as a Scene. (You may need to click on the plus button in the top right of the dialogue to reveal these settings)

3)File > Export > 2D Graphic. Set size as required in the Options dialogue and export your model in whatever file format you prefer.

4. SAVE YOUR MODEL'S SKP FILE!!!! We are about to radically change it.

5. Fill the entire model with 100% black colour.

6. Group the entire model.

7. In the Entity Info dialogue uncheck Cast Shadows and Receive Shadows. (You may need to click on the plus button in the top right of the dialogue to reveal these settings)

8. In the Shadows dialogue check Display Shadows and then move the Time slider to the extreme left or right. This will ensure that your model is a 100% solid black.

9. If you have moved your model in any of the previous operations click the Scene button in the top of the modeling window to restore your camera position.

10. File > Export > 2D Graphic. Export with exactly the same settings you used to export your model. (Warning these settings are not always "sticky". Open Options and set the export size by hand again.)

This will give you an image which is a solid black mask of your model on a white background. You need to invert it and create a mask from it in Photoshop. I have made the following instructions backwardly compatible for any version of CS.

In Photoshop open both images (I shall call them Model and Mask).

In the Mask image:

1. [i:3snv35lk]Image > Adjustments > Invert[/i:3snv35lk]

2. [i:3snv35lk]Select > All[/i:3snv35lk] and [i:3snv35lk]Edit > Copy[/i:3snv35lk]

In the Model image:

3. Double click [i:3snv35lk]Background[/i:3snv35lk] in the [i:3snv35lk]Layers Palette[/i:3snv35lk] to convert it to a layer.

4. [i:3snv35lk]Layer > Layer Mask > Reveal All[/i:3snv35lk]

5. [i:3snv35lk]Alt Click[/i:3snv35lk] the white layer mask icon in the [i:3snv35lk]Layers Palette[/i:3snv35lk] to edit it directly. (The image will turn white)

6. [i:3snv35lk]Edit > Paste[/i:3snv35lk] (Your Mask image will be pasted into the layer mask and will show on the screen)

7. [i:3snv35lk]Click[/i:3snv35lk] in the Image icon in the [i:3snv35lk]Layers Palette[/i:3snv35lk] to deselect the mask and re-select the image.

Bingo!! Your model is now surrounded by transparency.

If you try this you will see it really isn't as complicated as it looks …….. 

......... and it works ..... 

Good luck and have fun.

David Mac