Using Bitmap as alpha map of a cone

Question

Hi,

I'm wondering if i can use a bitmap to set alpha channel of a cone in wpf 3d :

Black = > alpha = 0 %

white => alpha = 100 % (more probably 80 % to see inside alpha difference ...)

Answer 1

WPF doesn't have any built-in mechanism for this. I think the easiest way is to:

1. Convert the Bitmap to a Geometry using a tracing library such as the potrace mentioned by Lie Ryan.
2. Simplify the Geometry to a polyline using GetFlattenedPathGeometry()
3. Convert each line segment in the resulting geometry into a 3D triangle from (x,y,0) to (0,0,z) where "z" is the height of the cone.
4. Build the Positions and TriangleIndices of a MeshGeometry3D and set its Material to a SolidColorBrush with the desired opacity.

Steps 2-4 are all extremely easy. Step 1 may be difficult from the standpoint of selecting an appropriate third-party bitmap tracing library and figuring out any P/Invoke or COM Interop required to call it from C#. Use BitmapSource.CopyPixels to get the bits to pass to the libraray and construct the Geometry from the result by drawing on an open StreamGeometry (StreamGeometry.Open).

Answer 2

Hi,

I've found a way to do what i want ...

I take each pixel of a bitmap and make a solidbrushcolored polygon with it (only if the pixel is not black to see color or white better ) !

But because of performance issue i've choose to rezize it to 32 x 32 !

To give a light effect i've use a emmitive material.

But it looks a bit pixellized .. and i'm afraid of using so much polygon to just one bitmap ... any idea ???