Use altitude: f32 and index: u32 instead of respectively position: vec3 and tex_coords: vec2

It reduces GPU memory usage from 20-21MiB to 16-17MiB.

src/main.rs

@@ -38,17 +38,38 @@ fn main() {
                 uniform mat4 persp_matrix;
                 uniform mat4 view_matrix;
 
-                in vec3 position;
                 in vec3 normal;
-                in vec2 tex_coords;
+                in uint index;
+                in float altitude;
 
                 out vec3 v_normal;
                 out vec2 v_tex_coords;
 
                 void main() {
                     v_normal = normal;
-                    v_tex_coords = tex_coords;
-                    gl_Position = persp_matrix * view_matrix * vec4(position * 0.005, 1.0);
+                    uint index_mod = index % 6u;
+                    uint index_div = index / 6u;
+                    uint z = index_div / 250u;
+                    uint x = index_div % 250u;
+                    if(index_mod == 0u)
+                        v_tex_coords = vec2(0, 0);
+                    else if(index_mod == 1u || index_mod == 4u)
+                    {
+                        v_tex_coords = vec2(0, 1);
+                        x++;
+                    }
+                    else if(index_mod == 2u || index_mod == 3u)
+                    {
+                        v_tex_coords = vec2(1, 0);
+                        z++;
+                    }
+                    else //if(index_mod == 5u)
+                    {
+                        v_tex_coords = vec2(1, 1);
+                        x++;
+                        z++;
+                    }
+                    gl_Position = persp_matrix * view_matrix * vec4(vec3(x, altitude, z) * 0.005, 1.0);
                 }
             ",