I don’t understand what you mean by making “a single sprite”. Normally, the GeomPoint interface is used to make a cloud of hundreds or thousands of sprites. The whole point of the interface is to allow you to collect many points into a single Geom object so you can render them with just one call. If you are going to have one sprite in each different node, then you might as well use the Billboard interface, which is much easier to use but slower for lots of sprites because each object is its own node.
But maybe you’re planning on constructing a cloud of sprites one at a time, and then flattening them all together? That might work, though I’ve never tried it. But it would be a slow way to build it.
I don’t know what you mean about measuring the distance from the camera to the tree. You can use standard Panda scene-graph operations to measure distances between any two nodes; for instance camera.getDistance(tree). But this won’t help you much to fit a flat perfectly on top of an existing model. There’s a whole science for doing this precisely; you’d need to do involve the lens projection (because the field of view makes a difference).
Again, all this is much easier with the billboard interface, because there you’re just dealing with a model in model space. No camera space is involved (much).
As to setRenderModeThickness(), when you’re in perspective mode then this is the same thing as Panda3D units, up to the limit of size supported by your graphics card (most cards will only render particles up to a certain size and no larger).
If you want to do it like Ogre imposters I think they use an orthographic camera with width and height same as the bounds of the model, render to a texture buffer then apply that to a billboard with the same width and height as bounds of the model and add it to the LOD.
I have a tree that I just make a .png for outside of Panda, since the tree look pretty much the same from any direction, then I just apply it as a texture to a billboard or a simple cross quad model.
How exactly? Is it the “film size” you are talking about?
Now that i think about it it does sound pointless, I can just add vertices to the geom in the first place.
what do you mean? Billboards are just a task that repositions the node to face the camera in some way, right?
Here Im using sprites to be able to have 1 geom and I’m making a new texture for the sprites, which replaces the actual model with LODing.
If I used billboards I wouldnt be able to flatten them and I would still need to create the texture the same way.
That looks right, use setFilmSize(wid,hi) on an OrthographicLens object and set that as the lens of a camera. I guess the camera then points to a tree model and only renders that model to texture. Maybe saying textured card is better than billboard because you don’t need that rectangle to always rotate to face the camera, it only needs to be oriented once to face the camera since it is the more distant model of the LOD and get switched by the more detailed model as the camera gets closer.