|06-13-2012, 07:14 PM||#1|
WW what is best resolution
I am plan to use WW to render 2 inch resolution data (at best resolution).
I need to use a flat globe and a mercator' projection.
I have check the source code, and it seem that WW core (CPU part) use double resolution so i think i'ts ok to handle the 2 inch resolution all around the globe.
But during the rendering and AFAIK the GPU convert all vertex to float ...
So in this case i loose a lot of resolution and result will be jitter data ...
My question :
is WW have a limitation to the maximum resolution data due to float conversion by the GPU?
|06-14-2012, 06:23 PM||#2|
WWJ Technical Manager
Join Date: May 2007
GPU hardware typically has low precision floating point, very often less than 32 bits. To get around that, geometry has to be specified to the GPU in small numbers. WW passes all geometry to the GPU relative to some geometry-specific reference point, such as the center point of a sector. A modelview transform is established to move these relative positions into world coordinates. This is the purpose of the push/pop ReferenceCenter system you see in WW's shape and terrain implementations.
If you are using WW's geometry (shapes and terrain) then I don't know why you'd be seeing jitter. There is no practical limit to the resolution that WW can display.
|06-14-2012, 10:17 PM||#3|
Join Date: Nov 2006
Location: Mojave & Oxnard California
This may be because you are painting each pixel many times over.
If you using your 2 inch resolution data at a view altitude of 100 miles that would be thousands of data for each pixel.
You can use an integer rather than a double to figure that out.
If you have 1600 horizontal pixels on your screen then what would the width of the view be with 2 inch for each pixel?
1600 x 2" = 3200" which is 267 feet
If your viewing your data and the view width is several times that then each pixel is in effect being painted several times.
WWJ uses tiled image layers with levels for different resolutions (overviews). dstile will create tiles with the highest resolution and overviews at lower resolution.
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