Creating blend masks

[Patrick Vibert]

I use paintshop pro and Global mapper for creating scenery and would like to know if anyone knows of how to automate the ceation of blend masks ?

Thanks for any answers
Patrick

 

[arno]

Hi Patrick,

If you want to automate it, the first question would be automate using what? Do you have some data for the blend mask or so. Without that it would remain an artistic (and manual) process to put it in.

The creation itself should be quite straight forward, you just have to paint the right channel of your image.

 

[Timmo]

How about this (im a photoshop user so terminology might be different) Ill also assume you know how to work your photo editing software.
1) create a new layer and positionally lock it to your aerial image
2) create a selection based on the boundary you want to use for your blend (i.e. For an island you could use the magic wand/select tool to select the water/shoreline/blue pixels). For a more generic blend (i.e blend the edges of a rectangular aerial photo) just use one of the 'normal' selection tools and draw a box just inside the border of the aerial image.

3)transfer this selection to the new layer (You want to have the bits that you DONT want showing selected)
4)Use the paint bucket fill to colour this selected area Black (this will mean this part of the aerial image wont show in the sim)
5)Using a large, blurry brush tool, with a white paint colour, go around the edge of your selection centering the brush on the edge of the selection: this will only paint in the selected area so the resultant effect will be a nice blend from white (full opaque) to black (full transparent)

Export just the new layer as a greyscale tiff/bmp and resample it with the original aerial image.

Make sense?

 

[Timmo]

Oops- just realised you are using global mapper.

If you have a polygon of your arial extent, simply create 10 or so concentric buffers INSIDE this, give them a greyscale colour ramp. Colour the aerial extent polygon WHITE, the background BLACK with the buffer polys going from white > Grey > Black as they move out.

For Islands and Shorelines, I ended up digitising polgons for all water features. From this I could create the water mask (Colour water polys black, white background, then export image). I could also buffer these to create the blend mask. This allowed me to export three images from GIS: The image, the water mask and the blend mask as Geotiffs...It takes a bit of intial work but if you have high quality shoreline data you are 80% there

 

[scott967]

This is something I play with as well. I use GIMP, but mostly I use a gradient brush with a black -> white gradient. I might use a mode such as darken only. It still is too much art. What I want is to draw an inner poly, outer poly, and have a uniform gradient between the two. This would also help for work I've done on eliminating airport mesh plateaus by interpreting mesh as greyscale images.

scott s.
.

 

[meshman]

withdrawn.

 

[HolgerSandmann]

Hi guys,

in Photoshop you can create gradients on the inside or outside of selected areas with the feathering option in the selections menu; that's how I create gradual transitions for my blending masks.

Cheers, Holger

 

[crushnik]

in Photoshop you can create gradients on the inside or outside of selected areas with the feathering option in the selections menu; that's how I create gradual transitions for my blending masks.

Holger, given that this post is over 12 years old, I wonder if you have any 64-bit insight to feathering.

I was pretty good at feathering inside and outside of edges in my Paint Shop Pro days (sadly my old program just can't handle 2 gigabyte files), but I am not getting anywhere in Gimp.

I created a blendmask that has white where my photoreal scenery should go and black where my hydro shapefiles are burned in. I made a second white layer, then switched to my original layer and selected all the black pixels. Tried all morning to feather the edges, where I would have a soft transition beginning at the edge of my water's edge that quickly blends into my vector. It feels like I am doing everything right, but I'm not getting anywhere.

Any thoughts?

 

[falcon409]

. . . . . .I created a blendmask that has white where my photoreal scenery should go and black where my hydro shapefiles are burned in. I made a second white layer, then switched to my original layer and selected all the black pixels.
Any thoughts?

Actually I do the same but I then select the white layer and select Gausian (sp?) Blur and apply that. It "feathers" the edges quite nicely and I've done hundreds of sceneries this way.

 

[crushnik]

Trying to figure this out on Gimp... When you feather, does your selection extend into the black or does it pull back, into the white? And when you have a waterbody that ends on one tile and continues on another, do you have a visible seam?

What program do you use?

Actually I do the same but I then select the white layer and select Gausian (sp?) Blur and apply that. It "feathers" the edges quite nicely and I've done hundreds of sceneries this way.