What's the difference between Speed Trees and the billboard trees?
Speed Trees is a technology developed Interactive Data Visualization (IDV), which renders trees directly on the video card using the faster more powerful graphics processor unit (GPU) instead of the slower program to CPU to video card route which is the older way of rendering trees, and the way which the billboard trees are rendered.
https://store.speedtree.com
Using the GPU instead of the old memory to CPU to video card, the geometry is rendered much quicker and textures can be applied much quicker. The quality of the trees, of course, is all up to the 3d artist or content creator who made them. Using this faster rendering technology, means that these trees can be animated as we see with them blowing in the wind, which I think was a bit over the top when they were first introduced, and always tuned them down, or used a script (by Otto I think his name is) to turn off the animation totally. This aspect has been fixed in the latest Speed Trees in T:ANE.
Billboards, as mentioned take a lot more work for the computer tor render, and in some cases cause a big performance hit. The reason is it's more complex to load the data into memory by the program, generate the mesh and apply the textures and do all the extra work by the CPU, then finally send them on to the video card for rendering.
There are advantages and disadvantages to both technologies. For older systems, with weaker graphics cards (GPUs), and faster CPUs, the older billboards will work better to a certain extent, and gets laggy and bound up by the Speed Trees.
Billboards only have a single rendering view. The geometry is basically a simple planar mesh with images plastered on them. Think of them as mylar sheets with pictures on them. A now long gone art and architectural supply store Charrette used to sell mylar sheets with trees printed on them for this purpose. Like their computer equivalents, the images were crisscrossed into a star pattern so that there was an image of the tree on all sides, though a single image.
Billboards suffer from an alpha-blending issue since TS2010, and do not always render well. In TS12 some became invisible, or nearly so and rendered like ghostly objects. This aspect was fixed in T:ANE so that both tree-types can be used. But then there's that multiple flat image issue with billboards. In T:ANE, and in other Trainz versions, the trees have distinct surfaces, which looks odd when they all face the same way.
Billboard meshes are double sided. This means that the image is rendered on both sides of the mesh, making extra work to render the trees. *This is also an issue with grass, and in particular grass splines, but they're not in the discussion now.
Billboard trees are images of real trees, yes someone photographed actual trees and used images of them to make the assets.
Speed Trees, on the other hand, are made up from libraries of specific tree types. The content creator can then scale and adjust the trees to suit their liking and needs using sliders and tools. It's this aspect of the Speed Trees which is not always great, due to many being way to big and clumsy - like the built-in ones, which are actually from a tree library available from IDV.
Speed Trees work well on the newer more powerful graphics cards and CPUs because a bulk of the work is done on the video card directly. The data takes a quick path via DMA (Direct Memory Access) from memory to the GPU where they are assembled using the supplied primitives. A primitive is a basic geometric shape which exists as part of a library. Leaves, branches, bark, etc. can be considered primitives. This means instead of trying to spit out the whole tree at once, the pieces are picked up using the code and assembled quickly in memory and displayed quickly. This is not new technology, by the way, earlier graphics programs and even graphics terminals had special chips with basic shapes in them to call up when needed to help speed things up.
Speed trees can be scaled automatically and on the fly. Rotate or move a Speed Tree, unless created at a fixed size, and the size and sometimes its shape can be altered. With billboards, you need a separate size for each individual tree, which means there's actually more of them needed to fill a space.
So that's the basics behind Speed Trees. They do have their advantages, and disadvantages just like the billboards do.
For those looking for great billboard trees in older Trainz versions such as TS2009 and below, check out those created by dmdrake (Dave Drake). His trees are par non and work well for just about every situation.
For later Trainz versions, TS12 and up look for Clam1952's trees. His CL series render well, and he also created a T:ANE version which renders quicker in that program. There are other too by toxa_batoxa (begin with tb), and many, many others. Download try them and delete them if they are a render hog. I found some of the forest series trees look great, but render too slowly - FYI.
Hope this helps.
