Matthew,
You can construct two vectors (Vector3d's in java) from the 3 points (A, B,
and C). The normal is simply the cross product of these (normalized)
vectors. Remember that the cross product of 2 vectors is a vector that is
perpendicular to both of these vectors.
vector1 = new Vector3d(C.x - A.x, C.y - A.y, C.z - A.z);
vector2 = new Vector3d(B.x - A.x, B.y - A.y, B.z - A.z);
vector1.normalize();
vector2.normalize();
normal = new Vector3d();
normal.cross(vector1, vector2);
If the normal turns out to face the wrong way, either negate it or reverse the
order of the cross product (i.e. normal.cross(vector2, vector1);).
Hope this helps,
-guillermo
[EMAIL PROTECTED]
Matthew Warren wrote:
> Hello,
>
> I have a situation where I need to calculate the normals of a surface for
> shading.
>
> The surface is represented as an [][] of hieght values, and because of this
> I believe I cannot use the triangulate and generatenormals classes as the
> triangulate class may not always return the surface I need.
>
> So, I can generate my own TriangleStripArray from the data but need to
> calculate the normal for each triangle. I have just made a quick search of
> the net and so far have only found lecture notes and papers etc. that talk
> about it a lot, but dont actually tell you how to do it...
>
> I imagine the code is quite simple, given 3 points determining a triangle.
>
> If someone could tell me the either the code to do it, or the math formula
> to compute the normal I would be very grateful.
>
> Thanks,
>
> Matthew.
>
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