   how to simulate tree's movement in wind
  I already read much material about how to create trees and its movement in wind.   However, due to I am not very familar with graphics programing, so it's a little difficult for me to simulate tree's movement in wind.  By Now, I have created a tree's trunk with small branches, but i dont know how to create tree's leaves.  Will someone share me with pratical material(inluding according source code if possible),thank you.   
  Render groups of leaves as an alpha-tested billboard-sprite.To simulate wind, rotate the sprite back and forth.billboard spritesalpha testingimproved alpha testing;  How realistic do u want it to be? The usual method is to clump leaves together into bundles and apply a simple oscillation on them based upon the perceived wind force, offset the oscillation a little from each other to give that decoupled look.I'm not sure if this is done in a shader or at a higher level anymore, but that's how it's usually done.Good Luck!-ddn   ;  You can check GPU Gems 3's article here: http://http.developer.nvidia.com/GPUGems3/gpugems3_ch06.html;  Firstly, thank you all. Yesterday, my pc is affected by viruses  and fail to log in the forum, so sorry to be late for your enthusiastic help.----------------------------------------------------------------------------K1nG Gr4H4m: "You can check GPU Gems 3's article here: http://http.developer.nvidia.com/GPUGems3/gpugems3_ch06.html"Yes, actually I am studying the source code of the gpugems3_ch06, but there aren't any leaves in the branches. So I want to get some relative material which teach me how to create leaves. -----------------------------------------------------------------------------ddn3: "How realistic do u want it to be? "I want to create tree's in different distance: near, middle and far.  So if the trees are near the camera, I want to create the trees with polygons; while the trees are in the middle distance, I want to create them with billboard or other technique which I haven't made decision. ddn3: "The usual method is to clump leaves together into bundles and apply a simple oscillation on them based upon the perceived wind force, offset the oscillation a little from each other to give that decoupled look."I have read some papers that make use of the leaves cluster to create leaves, but I dont know how to do from scratch.------------------------------------------------------------------------------Hodgman: "Render groups of leaves as an alpha-tested billboard-sprite.To simulate wind, rotate the sprite back and forth."I will search according information about alpha-tested billboard-sprite and will have a try.  No matter I succeed or not, I will post related info. ;  Now the problem I am facing is: how to create polygon leaves connecting to branch.  My branch description is:struct BranchDesc {// cone geometryfloat radiusFrom;float radiusTo;float length;// bending exponentfloat bendExp;// number of child branches along given branchsize_t childrenCount;// defines 'weakening' of childrenfloat childModifier;// positions range for children// valid range [0..1]float childrenPosFrom;float childrenPosTo;// defines orientations of children float childrenPosAngle;// child relative angle from parentfloat childrenDirAngle;};// Array of branch descriptions forms a tree description, and the tree's array is:static const BranchDesc WEAK_FIR_TREE_DESC[] = {//    r0r1  len    bendExp  childCount// mod  pFrom pTo posAngle   dirAngle    { 0.7f,  0.05f,   50.0f, 1.0f,    20, 0.25f, 0.2f,  0.95f,   deg2rad(135.0f), deg2rad(120.0f) },    { 0.25f, 0.0f,  15.0f, 0.5f,    3,  0.5f,  0.2f,  0.8f,    deg2rad(120.0f), deg2rad(30.0f) },    { 0.2f, 0.0f,    7.0f,  0.75f,   0 }};