Bump maps in inkscape?

JMan90 · Postby **JMan90** » Mon Jul 26, 2010 11:37 pm

Hi all,
I was reading how to create lighting effects in an online book on Inkscape. As I understand, the lighting filters, use the objects alpha channel as the bump map for the lighting filter. I was wondering if it is possible to manipulate the alpha channel directly. For instance, setting a gray-scale image into the channel.
Thanks,
Vance

Postby **brynn** » Tue Jul 27, 2010 6:17 am

Well the alpha channel, by definition, carries transparency info. While grayscale, to my knowledge, contains no transparency.

What are you trying to do, create a new filter or edit a pre-existing one maybe? Have you checked out the Filter Editor?

If you were to apply a filter which uses one of the lighting primitives, you could then access and edit the alpha channel. Although not with Inkscape. The filters all basically apply a bitmap, or raster graphics image, or portions of it, like the alpha channel, to the vector image created in Inkscape. I don't think there is any way, using Inkscape, to change the alpha channel info.

Postby **druban** » Tue Jul 27, 2010 6:27 am

If you want to design your bump map in inkscape you will have to export it as a bitmap and use the gimp or ps to paste it into your image's alpha channel and then bring it back into inkscape.
You might consider using the layer blend modes -multiply or screen - to superimpose a lighting effect overall and this might be faster and cleaner than a raster effect.

JMan90 · Postby **JMan90** » Wed Jul 28, 2010 11:05 pm

Thanks guys. I'll try out the superimposing technique, and also exporting it to GIMP. I thought I would get an email when there were replies, that's why I took so long to respond.

Postby **prkos** » Thu Jul 29, 2010 5:55 pm

I have a feeling it can be done using Filters but I haven't had time to test it, I'll reply if I find something.

RobA · Postby **RobA** » Fri Jul 30, 2010 1:37 am

prkos wrote:I have a feeling it can be done using Filters but I haven't had time to test it, I'll reply if I find something.

Yes you can. Under the Colour matrix filters there is a "Luminance to alpha" preset that turns a B&W image into an alpha bumpmap.

Here is an example:

: bump.png (59.6 KiB) Viewed 6860 times

And the Filter Dialog. Note the use of the Image primitive to load the bump map.

: 2010-07-29_113138.jpg (90.08 KiB) Viewed 6860 times

I've also attached the SVG file (with the bump map image embedded)

-Rob A>

Postby **prkos** » Fri Jul 30, 2010 3:19 am

This is awesome! Thanx ffaat!

Postby **brynn** » Fri Jul 30, 2010 3:56 am

Yes, awesome Rob!

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