Only one shader needed

resources/shaders/heightmap1.frag

-#version 410 core
-out vec4 FragColor;
-
-in vec4 vertexColor;
-in float colorCoord;
-in int colorOverridden;
-
-uniform sampler1D colorscheme;
-
-void main(){
-  if(colorOverridden == 1){
-    FragColor = vertexColor;
-  }
-  else{
-	  FragColor = texture(colorscheme, colorCoord);
-  }
-}

resources/shaders/heightmap1.vert

-#version 410 core
-layout (location = 0) in vec3 aPos;
-
-out vec4 vertexColor;
-out float colorCoord;
-out int colorOverridden;
-
-//perspective related uniforms
-uniform mat4 model;
-uniform mat4 view;
-uniform mat4 projection;
-
-//Scale related uniforms
-uniform float scale;
-uniform float minZ;
-uniform float maxZ;
-uniform float bad_z_value;
-
-//Cross section plots lines related uniforms
-uniform int plotLinesEnabled;
-uniform vec3 plotLineAlongX_color;
-uniform vec3 plotLineAlongY_color;
-uniform float plotLineAlongX_y;
-uniform float plotLineAlongY_x;
-uniform float plotLineHalfThickness;
-
-void main(){
-	vec3 position = aPos;
-	if(aPos.z != bad_z_value){
-		position.z -= minZ;
-		position.z *= scale;
-		position.z += minZ;
-	}
-	else{
-		position.z = minZ - 0.5 * scale * (maxZ - minZ);
-	}
-	gl_Position = projection * view * model * vec4(position, 1.0);
-	colorCoord = (aPos.z - minZ)/(maxZ-minZ);
-	vertexColor = vec4(position.z, 0.0, 0.0, 1.);
-  colorOverridden = 0;
-
-  //Check if on cross section line
-  if(plotLinesEnabled == 1){
-    if(abs(position.x - plotLineAlongY_x) < plotLineHalfThickness){
-      colorOverridden = 1;
-      vertexColor = vec4(plotLineAlongY_color, 1.);
-    }
-    else if(abs(position.y - plotLineAlongX_y) < plotLineHalfThickness){
-      colorOverridden = 1;
-      vertexColor = vec4(plotLineAlongX_color, 1.);
-    }
-  }
-}