Get positive vertex co-ordinates for mesh when inside vertex shader, to prevent heightmap repetition

Question

I have got a plane mesh of size 2 by 2, subdivided 32 times as in: https://docs.godotengine.org/en/3.0/tutorials/3d/vertex_displacement_with_shaders.html
I am applying a heightmap texture on it as:

shader_type spatial;
uniform sampler2D htmap;
void vertex() {
    float height = texture(htmap, VERTEX.xz).x;
    VERTEX.y += height;
}

Since the x & z co-ordinates go from -1 to +1, my heightmap gets repeated in the 4 quadrants:
https://ibb.co/nz295sH

I can pass the mesh size to prevent this(2.0 in this case as its a square mesh). But whats the usual way to avoid this?

Answer 1

Hello,
You should use the UVs when sampling a texture:

float height = texture(htmap, UV);

In the case of a PlaneMesh the UVs are setup for you the way you expect them to be in this case.