The tutorial link:
https://www.bilibili.com/video/BV1ih411n7N8?p=16&vd_source=29148d8c9f4eb2dbc06da56b612eed35 (P14-16)
The main point of this tutorial is billboard function. This is a very magic function. I can change the design of the tree crown freely.
Base Color
Color = Base color
HueShift can create the second color
NormalAdd can increase the ratio of base color
NormalColor can increase the ratio of HueShift color
UndersideColor can change the brightness of HueShift color
Highlight can make the tree looks growing
Here is the example I made to show the function more clearly.
Other
Billboard
Actually, I can't fully understand how to make the effect by seeing this graph. In fact, the tutor also does not fully understand, but he shows a link to let us know which tutorial he is referenced for. By the way, I face trouble after I follow the tutorials.
My first version
To save my time, I first use a simple sphere to test whether I make the graph correctly. Obviously, it looks strange. I think the problem is because the sphere is too simple and can not make the level of leave. Therefore, I make the shape of a tree crown by using zbrush.
It stills looks strange, the direction of leave is not similar to the tutor. The gap between the leaves is huge. (I try to copy one more tree crown put into the left tree, it stills strange)
When I turn to the back. OMG...
I tried to change all the parameters which affect Billboard. Finally, I found that the problem occurs on TransformVector. I made "Camera Space to Local Space" then "Tangent Space to World Space" before. In conclusion, the second space of the first TransformVector must be the same with the first space of the second TransformVector. It was just my careless mistake when I followed the tutor.
Final Result
The result by using simple sphere
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