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);
                 }
             ",
 

src/support/mod.rs

@@ -59,12 +59,12 @@ where
 pub fn load_ground(display: &Display) -> VertexBufferAny {
     #[derive(Copy, Clone)]
     struct Vertex {
-        position: [f32; 3],
+        altitude: f32,
         normal: [f32; 3],
-        tex_coords: [f32; 2],
+        index: u32,
     }
 
-    implement_vertex!(Vertex, position, normal, tex_coords);
+    implement_vertex!(Vertex, altitude, normal, index);
 
     let mut vertex_data: Vec<Vertex> = Vec::new();
 
@@ -72,6 +72,8 @@ pub fn load_ground(display: &Display) -> VertexBufferAny {
 
     let lines: Vec<&str> = contents.split('\n').collect();
 
+    let mut index: u32 = 0;
+
     for lines_index in 0..lines.len() - 1 {
         let line = lines[lines_index];
         let next_line = lines[lines_index + 1];
@@ -88,42 +90,48 @@ pub fn load_ground(display: &Display) -> VertexBufferAny {
             // First triangle.
 
             vertex_data.push(Vertex {
-                position: [lines_index as f32, column, columns_index as f32],
+                altitude: column,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [0.0, 0.0],
+                index,
             });
+            index += 1;
 
             vertex_data.push(Vertex {
-                position: [lines_index as f32, column_right, (columns_index + 1) as f32],
+                altitude: column_right,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [0.0, 1.0],
+                index,
             });
+            index += 1;
 
             vertex_data.push(Vertex {
-                position: [(lines_index + 1) as f32, column_below, columns_index as f32],
+                altitude: column_below,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [1.0, 0.0],
+                index,
             });
+            index += 1;
 
             // Second triangle.
 
             vertex_data.push(Vertex {
-                position: [(lines_index + 1) as f32, column_below, columns_index as f32],
+                altitude: column_below,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [1.0, 0.0],
+                index,
             });
+            index += 1;
 
             vertex_data.push(Vertex {
-                position: [lines_index as f32, column_right, (columns_index + 1) as f32],
+                altitude: column_right,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [0.0, 1.0],
+                index,
             });
+            index += 1;
 
             vertex_data.push(Vertex {
-                position: [(lines_index + 1) as f32, column_below_right, (columns_index + 1) as f32],
+                altitude: column_below_right,
                 normal: [0.0, 0.0, 1.0],
-                tex_coords: [1.0, 1.0],
+                index,
             });
+            index += 1;
         }
     }