Short Grass Rendering
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Most of the demos for grass I see use tall prairie looking grass. But the billboard techniques do not look good when viewed from a bird's eye. Since I want to render short grass (like a lawn) where if they player looks down it will sort of be a "bird's eye" view, I have doubts about the billboard approach. Does anyone have experience with this? Right now I am leaning towards a shell/fin system, but I would still like advice from anyone with experience in short grass rendering before starting.
Besides billboards or using a massive amount of little polygons, you may want to look at
"Steep parallax mapping"
Which is nothing but improved parallax mapping. There is a screenshot with some test grass and a reference to a useful paper on my blog here:
http://tower22.blogspot.com/2010_06_01_archive.html
Notice that my implementation didn't use self-shadowing so far. You can improve the results by taking more samples, varying the grass blade length & colors with some noisy maps, and apply self-shadows. Besides grass, this shader can also be used for carpets or fur. You could also play around a little bit with the blur directions to simulate some wind.
Rick
"Steep parallax mapping"
Which is nothing but improved parallax mapping. There is a screenshot with some test grass and a reference to a useful paper on my blog here:
http://tower22.blogspot.com/2010_06_01_archive.html
Notice that my implementation didn't use self-shadowing so far. You can improve the results by taking more samples, varying the grass blade length & colors with some noisy maps, and apply self-shadows. Besides grass, this shader can also be used for carpets or fur. You could also play around a little bit with the blur directions to simulate some wind.
Rick
like in Samoths link, use 4-16 layered polygons on top of each other
with small offset. And to get better outlook make bottom ones darker.
/Tyrian
with small offset. And to get better outlook make bottom ones darker.
/Tyrian
I implemented much of Boulangers stuff with great results, but for really short grass I'd suggest googling for "fur shell rendering" which is kinda what Tyrian is showing, but done automatically.
For short grass (well sometimes a bit longer too) I use way similar to Boulangers (quite a little bit different to achieve faster rendering). Here is a sample:
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