Normals

Todd Vanderlin — Tue, 22 Sep 2009 23:36:45 +0000

Finally got normals working for the height map. Brad helped me a ton with the math, thanks brad :). After making sure I had the right points its was pretty simple.

Here is an example to calculate normals for a grid in OpenFrameworks. Obviously this can be applied to any other language.

The image above we have four points on a plane. We need three of those points:

ofxVec3f p1(x1, y1, z1);

ofxVec3f p2(x2, y2, z2);

ofxVec3f p3(x3, y3, z3);

We now need a vector from p1 to p2 and p1 to p3.

ofxVec3f v1 = p1 - p2;

ofxVec3f v2 = p1 - p3;

We need the cross product of v1 and v2. This will give us our normal vector. Next we normalize that vector scale it and add p1.

ofxVec3f normalVec = v1.cross(v2);

normalVec.normalize();

normalVec *= 50.0;

normalVec += p1;

Now render from p1 to normal vector.

ofSetColor(255, 0, 0);

glVertex3f(normalVec.x, normalVec.y, normalVec.z);

glVertex3f(p1.x, p1.y, p1.z);

Todd Vanderlin » cpp

Normals