View Full Version : Help- Add layer mask and rivers - GIMP

03-26-2012, 09:54 PM
I have been following the Hand-Drawn Map Tutorial (for the Artistically Challenged) by Gidde @ the Cartographer's Guild. It was working out well for me up until he talks about rivers. I drew out my rivers an then he says (im going to quote it off the tutorial)

Step 2. Clean up the edges
Right-click on the River layer in the layers dialog, and click “Add Layer Mask…”. Check the box next
to channel, select Sea in the dropdown, check the Invert Layer Mask checkbox, and hit Ok. Next,
right-click the River layer again, and click Apply Layer Mask.

Now when i do that, all the rivers just vanish. Im just not sure if i missed a step or if im doing something else wrong. Any one have any idea why its doing that? Figure i will skip the step for now, but if his tip would make them look better, im all for using it. Assuming i can get it to work.


03-26-2012, 10:13 PM
Hi lokiie :)

First of all, Gidde's a "she" ;) To your question, it sounds like you may either be not clicking the Invert Mask checkbox, or maybe your Sea channel itself is inverted (to which the immediate solution would be to uncheck the Invert Mask checkbox). The only part of your rivers that *should* vanish in this step are the parts that bleed into your ocean/sea. Hope that helps, if not continue the thread and we'll keep working through it!

03-26-2012, 11:09 PM
Ah ok, sorry bout that, normally say he/she but my brain has been on the frits working on this. Its fun though so i don't mind too much. I actually do remember inverting the sea channel too so that must be my problem, as the "bleed outs" were all that showed. I think i had just misunderstood what the step was supposed to do. I had thought it would crisp the line edges for places were i messed up or something.

Thanks for the help, and great work on guide. There is no way i would have figured out any of this with out it lol I will be sure to post it on here when its done, it wont be perfect but it will do its job, which is a visual aid to help me write a fantasy/post apoc novel I'm working on.

03-26-2012, 11:14 PM
Ha, no need for apologies, just clarifying :)

Glad that helped, and that you're getting use out of the guide. Looking forward to seeing your map!

03-27-2012, 08:44 PM
Also, I would highly suggest learning the details about layer masks. Tutorials about how to do something are great, but it's more helpful in the long run in knowing WHY you are doing a specific step and I will tell you IMHO, learning about layer masks is a huge mental shift and give you that "eureka" moment. If you check my sig, there is a short tutorial on layer masks, including more of a "why" to use them.