Fix the valid umbra detection.
This looks better b/c every vertex will have one ray shooting at it, such that
we don't miss the corner.
This performs better too, due to the polygon intersection is removed and less ray
intersection. 2x performance for rect and circle for spot shadow in test app.
b/17288227
b/15598793
b/16712006
Change-Id: I4a5ee397b9e192e93c8e35e6260b499e3e38a6f4
Using the vertices, instead of ray casting for the triangulation.
This request a dynamic index buffer associated with vertex buffer,
so we update the VertexBuffer to support it.
The ambient shadow could be 3x-6x times faster for circle and rect now.
b/16712006
b/14257173
Change-Id: I2f22a8fe19bc59acee5c18e4a3a395acd5042a66
Now the theta = 0 should be on +x axis.
And cos(theta) should correctly represent x value.
Without this fix, the poly theta (from atan2) can be wrongly rotated 90 degrees.
Also, make sure the incoming polygon is CW for the shadow system.
This fix visual artifacts in recent regression for spot shadows.
bug:13553955
Change-Id: I9bbf54db094e7f133326da4dae4610962da849c1
Basically we compute the shadow as a strip of triangles, whose alpha value
is the strength of the shadow.
We use the normal to extend the geometry.
And we use static function and try to avoid new/malloc in the computation.
Change-Id: I382286f1cad351bd5ff983f76f446c075819dcaf
