I have created a primitive sphere. At runtime i’m generating a dynamic 2048x1024 texture for it. On this texture a tiny circle is drawn, which could be anywhere. I have the x/y of this circle on the texture, and consequently the corresponding UV coordinate. Now, i’d like to interpolate where exactly on my sphere [x,y,z] this little circle is located.

Does anyone know how I can accomplish this?

hi

i dont know if there is a helper class for this…

to get the uv-triangle, your uv is sitting in, you would have to loop through the IndexData of your Mesh and calculate for each triangle if it is the uv-triangle your searching for (use barycentric cooardinates to test if uv is in uv-triangle)

here i see a problem you would run into, if your mesh have multiple triangles with the same uvs (uv-mirrored models).

if you have the indicies of the uv-triangle calculated you can use them to retrieve the 3 verticles that make up the triangle.

i guess to get the actual Vector3D on the calculated triangle, you could use the Barycentric cooardinates of your uv-point. not shure about that.

Hope that makes sense…

80

thanks for this—i’ll investigate further.  Do you happen to know of an example of the BarycentricTest class?

hi

as far as i know there is no BaryCentrictest class available yet, so you must do the calculation yourself. cant give you much advice, because i just happend to learn about this the last days too.

look inside the HitTestRenderer.as in the function “getPreciseDetails” it uses barycentric coordinates to calculate if a Vector3D is inside a triangle in 3d space. i dont know if this calculation is done 100% correct, since the HitTestrenderer happens to not always (but in most cases) work correct.

For the purpose of getting the uv-triangle for a given uv, you wouldnt need to do this calculation in 3d, but as far as i understand, the concept and the math for 3d and 2d Barycentric coordinates are pretty much the same.

So doing some research about BaryCentric-Coordinates and looking into the HittestRenderer should give you a place to start.

There is a BaryCentricTest class in away3d.tools.utils (away3d 4).  Thanks, tho.. I will look in to it further.