Is Triangle CW or CCW with respect to a Ray

Graphics
1

Hi all,

Newbie here but really enjoying learning 3D in Monogame - been browsing this community site for about 50 hours in the last fortnight :slight_smile:

I have a quick question.

I have a Triangle with an intersecting Ray. How can I quickly find out if the triangle is CW or CCW with respect to the Ray?

Thanks.

2

You need to calculate the triangle’s normal vector using the cross product, and then compare that normal vector to the ray’s direction vector using the dot product

Vector3 normal = Vector3.Cross(p1-p0, p2-p1);
float normalDotRay = Vector3.Dot(normal, rayVector);
bool isCW = normalDotRay > 0; // or < 0, try what works
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