GLTRIANGLESTRIP

GLTRIANGLESTRIP, also known as GL_TRIANGLE_STRIP, is a primitive type in OpenGL used to render a connected strip of triangles that share vertices along a single chain. The first triangle is formed from the first three vertices: v0, v1, v2. Each subsequent vertex v_i (for i ≥ 3) creates a new triangle with the two preceding vertices, producing triangles in sequence: (v0, v1, v2), (v1, v2, v3), (v2, v3, v4), and so on. This arrangement reuses vertices, which can reduce the amount of vertex data and indexing required for rendering long connected surfaces.

In GL_TRIANGLESTRIP, the winding order of successive triangles alternates, so the front-facing direction flips from triangle to triangle. As a result, consistent face culling can be affected unless handled carefully. Techniques to manage this include reordering vertices, using degenerate triangles (by repeating vertices), or employing primitive restart to break a single strip into multiple segments within a single draw call.

Typical uses for GL_TRIANGLESTRIP include rendering long, regular surfaces such as terrain rows, cylindrical or braided meshes, and other meshes where many adjacent triangles share vertices. It is supported by modern OpenGL workflows via glDrawArrays or glDrawElements with the GL_TRIANGLE_STRIP mode, and by the historical immediate mode path as glBegin(GL_TRIANGLE_STRIP) / glEnd().

Compared with GL_TRIANGLES, triangle strips can offer performance benefits by reducing vertex specification and improving vertex reuse, but they offer less flexibility for independently controlled triangles. GL_TRIANGLE_STRIP is a common choice when rendering connected, strip-like geometry with regular topology.