OpenGL: Add vertices with vertex shader

5
votes

Tell me, please, how I can add new vertex in vertex shader?

4
openglshadervertex

4 Answers

7
votes

The vertex shader only transforms vertices. If you need to output additional geometry based on the input vertices a geometry shader is what you need.

3
votes

You can add vertices using a geometry shader http://www.opengl.org/wiki/Geometry_Shader

"A GS can create new primitives, unlike vertex shaders, which are limited to a 1:1 input to output ratio."

3
votes

You can't. That's what geometry shaders are for.

0
votes

It's not possible to create new vertices using a vertex shader; it can only transform vertices. The Khronos documentation for the vertex shader states:

A vertex shader receives a single vertex from the vertex stream and generates a single vertex to the output vertex stream. There must be a 1:1 mapping from input vertices to output vertices.

There are several options for adding new vertices:

  • Generate the new vertices on the CPU before rendering them.
  • Use a geometry shader for creating new vertices based on a given primitive.
  • Use tessellation for creating new vertices based on a given patch.