The rotation comes from a per particle expression. I wanted the leaves to scale up to 1 from 0 as they were born so I attached a ramp to a custom per particle attribute. There are creation expressions for the scale and rotation per particle and a runtime before dynamics expression to keep them rotating.
This ramp represents the particles scale over their lifespan.
Once I had established a preliminary animation/simulation I needed to create some leaves.
I acquired some textures from a range of sources including my garden and the internet. I 'cut them out' and color corrected them in photoshop.
I didn't want to model the leaves individually and had some bad experiences with rendering leaf textured cards with transparency in mental ray for all of the passes. I did some digging and discovered a Maya feature called 'Texture to geometry'. After toying with this feature I got some results I could use. Useless faces were shaded by a shader related to the texture's alpha, so I could select and delete them, leaving me with some weird leaves.
Unless I need these leaves to deform, the topology is acceptable. It is easy enough to remove non border edges and re-cut manually later. I wanted to work this way as I knew I may change the leaves later.
Following this all was required to do to move on was use an instancer to assign leaves to the individual particles. I used another creation expression per particle to choose random leaves from the instancer index. I duplicated leaves I wanted to favour and balance the appearance of the different coloured leaves.
All that remains for this section is to infinitely tweak and improve my animation! I have a good idea about the composition with the leaves and the empty space in the frame is intentional breathing space for my CG leaves!
In my next blog entry I will go over the lighting and probably the rendering too.
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