OpenGL Insights

168 II Rendering Techniques

11.3.2 Geometry Extrusion Using a Geometry Shader

The vertex shader–based extrusion method has the drawback of not being able to

render correct volumetric lines when they are viewed a long their own direction: the

triangle strip becomes visible at the grazing angle (Figure 11.5). The method using a

geometry shader–based extrusion does not suffer from this problem.

Figure 11.5. The visual error resulting from using the vertex shader–based extrusion while

viewing a line along its direction (left). Corrected version using geometry shader–based extru-

sion (right).

Given the two input vertices, the geometry shader extrudes an ...