210 lines
8.6 KiB
Text
210 lines
8.6 KiB
Text
Configuring 3D Clouds
|
|
=====================
|
|
|
|
3D clouds can be created in two ways:
|
|
- By placing individual clouds using a command (e.g. from Nasal)
|
|
- Using the global weather function, which reads cloud definition from
|
|
an XML file.
|
|
|
|
Placing Clouds Individually
|
|
===========================
|
|
|
|
Clouds are created using the "add-cloud" command, passing a property
|
|
node defining the location and characterstics of the cloud.
|
|
|
|
Location is defined by the following properties:
|
|
|
|
<layer> - The cloud layer number to add the cloud to. (default 0)
|
|
<index> - A unique identifier for the cloud in the layer. If a cloud
|
|
already exists with this index, the new cloud will not be
|
|
created, and 0 is returned.
|
|
<lon-deg> - Longitude to place the cloud, in degrees (default 0)
|
|
<lat-deg> - Latitude t place the cloud, in degrees (default 0)
|
|
<alt-ft> - Altitude to place the cloud, relative to the layer (!) in ft
|
|
(default 0)
|
|
<x-offset-m> - Offset in m from the lon-deg. +ve is south (default 0)
|
|
<y-offset-m> - Offset in m from the lat-deg. +ve is east (default 0)
|
|
|
|
The cloud itself is built up of a number of "sprites" - simple 2D textures
|
|
that are always rotated to be facing the viewer. These sprites are handled
|
|
by a OpenGL Shader - a small program that is run on your graphics card.
|
|
|
|
The cloud is defined by the following properties:
|
|
|
|
<min-cloud-width-m> - minimum width of the cloud in meters (default 500)
|
|
<max-cloud-width-m> - maximum width of the cloud (default min-cloud-width-m*1.5)
|
|
<min-cloud-height-m> - minimum height of the cloud (default 400)
|
|
<max-cloud-height-m> - maximum height of the cloud (default min-cloud-height-m*1.5)
|
|
<texture> - texture file of sprites to use (default cl_cumulus.png)
|
|
<num-textures-x> - number of cloud textures defined horizontally in the
|
|
texture file (default 4)
|
|
<num-textures-y> - number of cloud textures defined vertically in the
|
|
texture file (default 4)
|
|
<height-map-texture> - whether to choose the vertical texture index based on
|
|
sprite height within the clouds (default false)
|
|
<num-sprites> - Number of sprite to generate for the cloud (default 20)
|
|
<bottom-shade> - Light multiplier for sprites at the bottom of the cloud
|
|
(default 1.0)
|
|
<min-sprite-width-m> - minimum width of the sprites used to create the cloud
|
|
(default 200)
|
|
<max-sprite-width-m> - maximum width of the sprites used to create the cloud
|
|
(default min-sprite-width-m*1.5)
|
|
<min-sprite-height-m> - minimum height of the spites used to create the cloud
|
|
(default 150)
|
|
<max-sprite-height-m> - maximum height of the sprites used to create the cloud
|
|
(default min-sprite-height-m*1.5)
|
|
<z-scale> - vertical scaling factor to apply to to the sprite after
|
|
billboarding. A small value would create a sprite that
|
|
looks squashed when viewed from the side. (default 1.0)
|
|
|
|
|
|
The texture to use for the sprites is defined in the <texture> tag.
|
|
To allow some variation, you can create a texture file containing multiple
|
|
sprites in a grid, and define the <num-textures-x/y> tags. The code
|
|
decides which texture to use for a given sprite : randomly in the x-direction
|
|
and based on the altitude of the sprite within the cloud in the y-direction
|
|
if <height-map-texture> is set. Therefore, you should put sprite textures
|
|
you want to use for the bottom of your cloud at the bottom of the texture
|
|
file, and those you want to use for the top of the cloud at the top of the
|
|
texture file.
|
|
|
|
For example, the following Nasal snippet will create a cloud immediately above the
|
|
aircraft at an altitude of 1000 ft above /environment/clouds/layer[0]/elevation-ft :
|
|
|
|
var p = props.Node.new({ "layer" : 0,
|
|
"index": 1,
|
|
"lat-deg": getprop("/position/latitude-deg"),
|
|
"lon-deg": getprop("/position/longitude-deg"),
|
|
"alt-ft" : 1000 });
|
|
fgcommand("add-cloud", p);
|
|
|
|
Moving Individual Clouds
|
|
========================
|
|
|
|
Clouds may be moved by using the "move-cloud" command. This takes the following
|
|
property arguments.
|
|
|
|
<layer> - The cloud layer number containing the cloud to move. (default 0)
|
|
<index> - The unique identifier of the cloud to move.
|
|
<lon-deg> - Longitude to place the cloud, in degrees (default 0)
|
|
<lat-deg> - Latitude t place the cloud, in degrees (default 0)
|
|
<alt-ft> - Altitude to place the cloud, relative to the layer (!) in ft
|
|
(default 0)
|
|
<x-offset-m> - Offset in m from the lon-deg. +ve is south (default 0)
|
|
<y-offset-m> - Offset in m from the lat-deg. +ve is east (default 0)
|
|
|
|
Deleting Individual Clouds
|
|
===========================
|
|
|
|
Clouds may be deleted by using the "del-cloud" command. This takes the following
|
|
property arguments.
|
|
|
|
<layer> - The cloud layer number containing the cloud to delete. (default 0)
|
|
<index> - The unique identifier of the cloud to delete.
|
|
|
|
Global 3D Clouds
|
|
================
|
|
|
|
The global weather system uses sets of clouds defined in
|
|
FG_ROOT/Environment/cloudlayers.xml
|
|
|
|
The file has 3 distinct sections: layers, cloud boxes and clouds,
|
|
described below.
|
|
|
|
Notes for those editing clouds:
|
|
- All distances are in m. Note that this is in contrast to cloud heights
|
|
in METAR etc. which are in ft.
|
|
- The XML file is loaded into the properties system, so you can modify
|
|
the settings in-sim, and see the results by re-generating the cloud
|
|
layer. The simplest way to do this is to disable METAR, and control
|
|
the cloud layers using the Clouds dialog, and in particular the coverage.
|
|
- Texture files are in .png format, and have a transparent background.
|
|
To make the textures easier to edit, create a black layer behind them,
|
|
so there is some contrast between the background and the white cloud.
|
|
Having a grid based on the texture dimensions also helps, so you don't
|
|
bleed over the edges, which causes ugly sharp horizontal and vertical
|
|
lines.
|
|
|
|
Clouds
|
|
======
|
|
|
|
The cloud definitions are as described above for placing individual
|
|
clouds, but no position information is used (this is defined in the
|
|
cloud box and layers below).
|
|
|
|
Cloud Boxes
|
|
===========
|
|
|
|
The <boxes> section contains definitions of groups of cloads,for example
|
|
an entire towering CB mass.
|
|
|
|
The <boxes> section contains a number of named types, which are referenced
|
|
by the <layers> section, described below. Therefore, the names used are
|
|
completely user-defined.
|
|
|
|
Each of the named section consists of one or more <box> section,
|
|
defining a particular cloud type
|
|
|
|
Each <box> section contains the following tags:
|
|
|
|
<type> - The cloud to use, defined above
|
|
<count> - The number of clouds to generate (+/- 50%)
|
|
<width> - The x and y within which these clouds should be generated
|
|
<height> - The height within which the clouds should be generated
|
|
<hdist> - The horizontal distribution of the clouds within the area.
|
|
Equates to a sum of random distributions. Defaults to 1.
|
|
1 = even distribution, 2 = distributed towards the center.
|
|
3 = very strongly distributed towards the center.
|
|
<vdist> - The vertical distribution of the clouds. As for hdist.
|
|
|
|
|
|
If the /sim/rendering/clouds3d-density is less than 1.0 (100%), then a
|
|
proportional number of clouds will be displayed.
|
|
|
|
The following example shows a stratus cloud group, which consists of 5
|
|
st-large clouds and 5 st-small clouds, distributed in a box 2000mx2000m,
|
|
and 100m high, evenly distributed.
|
|
|
|
<st>
|
|
<box>
|
|
<type>st-large</type>
|
|
<count>5</count>
|
|
<width>2000</width>
|
|
<height>100</height>
|
|
</box>
|
|
<box>
|
|
<type>st-small</type>
|
|
<count>5</count>
|
|
<width>2000</width>
|
|
<height>100</height>
|
|
</box>
|
|
</st>
|
|
|
|
|
|
Layers
|
|
======
|
|
|
|
The <layers> section contains definitions for a specific layer type.
|
|
The layer type is derived from the METAR/Weather settings by FG itself.
|
|
|
|
Each layer type is a named XML tag, i.e.: ns, sc, st, ac, cb, cu.
|
|
If a layer type is not defined, then a 2D layer is used instead.
|
|
|
|
The layer type contains one or more <cloud> definitions. This
|
|
defines a type of cloud box, and a weighting for that type (<count>).
|
|
|
|
For example, the following XML fragment will produce 3 "cb" cloud boxes
|
|
for every 1 "cu":
|
|
|
|
<cloud>
|
|
<name>cb</name>
|
|
<count>3</count>
|
|
</cloud>
|
|
<cloud>
|
|
<name>cu</name>
|
|
<count>1</count>
|
|
</cloud>
|
|
|
|
Clouds are randomly distributed across the sky in the x/y plane, but the
|
|
height of them is set by the weather conditions, with a random height range
|
|
applied, defined by <grid-z-rand>
|