Outline effects in OpenGL

Question

In OpenGL, I can outline objects by drawing the object normally, then drawing it again as a wireframe, using the stencil buffer so the original object is not drawn over. However, this results in outlines with one solid color.

In this image, the pixels of the creature's outline seem to get more transparent the further they are from the creature they outline. How can I achieve a similar effect with OpenGL?

Answer 1

They did not use wireframe for this. I guess it is heavily shader related and requires this:

1. Rendering object to a stencil buffer
2. Rendering stencil buffer with color of choice while applying blur
3. Rendering model on top of it