Drawing billboards using geometry shaders

Simplifying geometry drawn in a distance is a common technique for lowering the processing power needed to render the whole scene. The simplest geometry that can be drawn is a flat quad (or a triangle) with an image depicting the look of an object. For the effect to be convincing, the quad must always be facing camera:

Flat objects that are always facing camera are called billboards. They are used not only for distant objects as the lowest level of detail of a geometry, but also for particle effects.

One straightforward technique for drawing billboards is to use geometry shaders.

How to do it...

1. Create a logical device with the geometryShader feature enabled (refer to the Getting features and properties of a physical device and Creating a logical device recipes from Chapter 1, Instance and Devices).
2. Prepare positions for all billboards with one vertex per single billboard. Store them in a vertex buffer (refer to the Creating a buffer recipe from Chapter...