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This is a technique for making a large grassy field in bryce without reducing your PC to a smoking pile of plastic and metal. The same technique can be used to make a distant forest while minimising the polygons and hence file size and render times.
The grass that we will be making will be made from a series of 2D picture objects. To do this we need to make or find a grass texture as well as a transparency map that will give the grass the “shape” we want.
For this tutorial, this is the grass texture I used - the angle seen in the grass texture matches the sort of lean I envisage the grass in the field to have. The jagged uneven look of the grass will be made with the alpha (transparency) map, so don't worry too much about trying to draw individual blades of grass in this part.
I then made the transparency map - this one was made in Adobe Elements using its default grass brush. This transparency map will give the grass its random sort of shape.
After creating the scene that you want to put the grass into, the next thing is to make the 2D grass picture objects.
To do this, firstly click on the “Da Vinci” figure in the “create” palette in bryce. Then load the grass and transparency maps that you just made into the appropriate channels as shown and click on the tick. This will then give you a grass object in your scene. You should then scale the grass so that its the right height and size when compared to everything else in your scene.
First move the grass to a height well above the rest of your scene and then view your scene in the “From Top” view mode - this will just make life a lot easier later. Move the grass object to one corner of the area you want to cover in grass. Now, with the grass selected, click on the Edit > Multi-replicate.
Make a row of grass objects across the width of the field in your scene (the x-direction) where you wish to have the grass. The number of grass objects you will need will depend on how big an area in your scene that you want to put grass in and on the size of your grass object.
When this is done, select all the grass objects in that row and use the Edit > Multi-replicate option again to make a rectangular pattern of grass objects that now covers roughly the area that you want to cover with grass (multireplicate in the z-direction this time). When you are doing these multi-replications, make sure that the “Size” is set to 100% and the “Rotate” is set to 0 degrees.
You should now have a rectangular shaped grid of grass objects that roughly covers your field (when viewed from above).
If we just dropped this lot of grass onto the field terrain, then we'd end up with artifacts in the resulting grass - i.e. there would be furrows or patterns/lines appearing in the grass. To make sure there aren't any, we need to randomize the positions of all the grass objects. We do this by using bryce's randomize function.
Go into the Edit palette and click on the randomize arrow - this will bring up a series of randomizing options. Choose the “2D disperse” option. Now click on the randomize dot and drag the mouse slowly over to the right while holding the left hand mouse button down - this will randomly move the selected grass objects around. When things are looking reasonably random and not too spread out, then you can release the mouse button.
The next step involves dropping the grass down to the terrain. To do this, select all of the grass and then click on the down arrow symbol next to this selection. This will then (after a short wait as bryce does some calculating) drop all the grass down to the terrain of the field.
If there's any obvious gaps or grass that has landed where it shouldn't then you can either add more grass to those gaps or move the wrongly placed grass out of the way respectively.
After rendering your field you will see, in general, a few small gaps in the grass. The easiest solution I've found here is to use a clone brush or cut and paste technique in a painting program to fix these problem areas.
The important thing to remember here is to clone an area from the grassy field from the same “depth” (or distance) into the field as the gap you will be filling - this will ensure that the haze effects with distance will remain consistent across the field.
After fixing up the gaps, you will have your grassy windswept field. The exact same technique can also be used to make other backgrounds such as a distant forest.
If you have any questions concerning this tutorial, feel free to send me an email at WastelandD@hotmail.com (make sure you spell that email address properly) and we'll see if we can find you an answer.