About Blendmask and Watermask

Hi Gary,

I hope I'm in the correct forum. I'm curious about something regarding making blendmask and watermask. I was reading a tutorial "Using Gimp to Create Water/Land and Blend masks," and in it, it tells you to make one layer as a watermask and another layer as a blendmask. So you have 2 layers here. If I understand correctly, a watermask is when you paint everything that is water in black. A blendmask is when you paint everything black on the map that you do not want to be shown in the sim. What I'm curious about is that is there a reason for having 2 separate layers, one for the watermask, and the other for the blendmask as opposed to having just one layer to create both the water and blendmask? It's just something I'm curious about but I'm going to follow the instructions laid out.

Hi Ken:

Technically one must specify in the *.INF which "Channel" in a specified image file is to be processed as a:

* Blend Mask


* Land / Water Mask

...in order for SDK Resample to properly interpret the Mask data.

In the graphics application, one can more easily distinguish the purpose and type of data to be output as separate Masks, by creating and maintaining Blend Mask and Land / Water Mask images either as separate layers (Channels) within a graphic file format which saves / preserves multiple layers without requiring that 'saved' layers be merged / combined / flattened.

Alternatively such Blend Mask and Land / Water Mask images may be saved as separate 1-layer raster files.

The method used by ACES in SDK documentation utilizes Masks which are 8-Bit gray-scale TIFF images

BTW: While technically SDK Resample 'can' process a number of graphic source file formats to make custom photo-real imagery land class BGLs, SBuilderX reportedly will internally process only certain *.BMP source file formats to make custom photo-real imagery land class BGLs prior to submitting the *.BMP and *.INF source files to SDK Resample.

CAVAEAT: Be aware that an inherent limitation of the *.BMP source file formats that SDK Resample will accept to make custom photo-real imagery is that such *.BMPs shall only have a single Alpha Channel.

Although some developers do utilize that Alpha Channel as a Mask, AFAIK, most developers follow the procedure method used by ACES in SDK documentation, that utilizes Masks which are 8-Bit gray-scale TIFF images that are separate from a *.BMP source file used for an actual visible Day or Seasonal / Night image.

When those Mask images are specified properly in the *.INF as "Channels", they are read and treated as data sources to assign scenery attributes of:

* Variable transparency (aka "Blend") of superimposed custom photo-real versus underlying land/water class

Blend Masks use up to 256 gray-scale steps ranging from near-Black (RGB 1,1,1) to near-White (RGB 254,254,254)


* Land / Water Masks turn On/Off a superimposed, translucent Hydro overlay (float, splash, wave specularity)

Land/Water Masks must use gray-scale steps of ONLY pure-Black (RGB 0,0,0) AND pure-White (RGB 255,2555,255)

IMHO, the "8-Bit gray-scale TIFF Mask" method may be regarded as the most practical and SDK compliant to use.

FYI: That "gray-scale masking" method is to be distinguished from an alternate method which requires "color" Masks (and therefore larger source file data set sizes :alert: ).

Such types of "color" Masks utilized by Maurizio Giorgi (aka "Maurizio_G") for certain freeware and OrbX FTX payware scenery packages, allow output of Blend Masks, Land and Water Masks, as well as some types of Land and Water class texture definitions, via pixel-based methods within the custom photo-real imagery BGL directly via SDK Resample.

Land and Water class texture definition methods using "color" Masks are to be distinguished from generation of those sub-types of Land and Water class texture definitions via CVX vector polygon objects compiled by SDK SHP2VEC.

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