Hi all,
I solved this problem. To help others I'll explain my ideas here, so other can
use this information as well.
The wrong part in my structure was the function were I modified the height
values.
To explain my optionion of the right way, it is required to understand how the
tiles are initialized.
Step 1: When the tile is added to the scene graph, it will be traversed in the
next frame. - TerrainTile.cpp, line 120
Step 2: If it is the first traversal, the tile's init() function is called. -
TerrainTile.cpp, line 143
Step 3: If no terrainTechnique is assigned, it assigns the terrainTechnique. -
TerrainTile.cpp, line 169
Step 4: Now a terrainTechnique should be available, so it's init() function is
called. - TerrainTile.cpp, line 184
Step 5: The drawable geometry is created from heightfield in
generateGeometry(). - GeometryTechnique.cpp, line 135
Step 6: The color- and transparency layer are created from imagelayer and
blending policy in applyColorLayers() / applyTransparency(). -
GeometryTechnique.cpp, line 135+
Step7: The created tile data buffer is assigned to the _newBufferData pointer,
so the next update traversal will use it as current data to display. -
GeometryTechnique.cpp, line 145 / 150
If the color / transparency or geometry data should be modified, it must be
done prior the data is used to compile the data to display.
e.g. To modify the geometry, you can subclass GeometryTechnique and overwrite
the init function. There in you can modify all of the tile's layers. afterwards
you call the baseclass implementation via
Code:
void myTerrainTechnique::init(int dirtyMask, bool assumeMultiThreaded)
{
// Modify the data
[...]
// Call base class implementation to init the tile correctly:
GeometryTechnique::init(dirtyMask, assumeMultiThreaded);
}
If you have to modify more than only the tile data you have to overwrite the
generating function.
Example:
In my case I want to cut holes in the terrain, this means the tile drawable is
not longer a regular grid of triangles. This irregular drawable must be created
by my specialized generateGeometry() function, I have to implement in my
subclassed TerrainTechnique.
I know it is a very simple approach, but oftern the first contact is quite
hard, so this may be a good starter for other beginners out there :)
So far, thanks to the community which helped me to reach this point!
I'll be back with my generateGeometry() problems ;)
Cheers,
Torben
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=34368#34368
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