Question

How can I get hard edges on my terain. I have a simple ambient and diffuse shader in GLSL. I think that the fragment shader is interpolating the vertex normals and causing smooth shading. Do you guys need my code or is there maybe some setting I can enable?

Current terain without hard edges:
http://twirlbound.com/uploads/terain.png

Answer 1

In your vertex shader, do something like this:

flat out vec3 v_normal;

In your fragment shader, something like this:

flat in vec3 v_normal;

flat tells the GL to give all the fragments rasterized for a triangle the same value. Which vertex’s normal is used depends on the current ‘provoking vertex’, set by calling glProvokingVertex.