Portrait Pixel Flow

Todd Vanderlin — Tue, 02 Feb 2010 17:49:13 +0000

Been doing some testing to find the flow of pixels in portraits. Above are a few attempts to find vectors in pixels based on surrounding pixels. In video this is achieved by simple comparing current frames to previous frames then calculating the velocity of the different pixels. Here I want to find the general flow of pixels through the image. The goal is to then have particles stream through the image to generate a representation of the image, some type of generative stipple drawing.

See large image here
Original Einstein image here
Original Obama image here

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 » vectors

Portrait Pixel Flow

Normals