🐎 Only render voxels w/ exposed faces.

The mesh generation of a chunk will now take account of a voxel
and its neighboring voxels and will only include the faces of
voxels that are exposed. This is a half-baked implementation
as there is no support for checking boundaries between chunks.

Author: andrewvy

src/chunk.c

@@ -6,39 +6,69 @@
 
 chunk *create_chunk(GLfloat x, GLfloat z) {
   chunk *new_chunk = malloc(sizeof(chunk));
-  new_chunk->blocks = (uint8_t *) calloc(1, sizeof(CHUNK_SIZE));
+  new_chunk->blocks = (uint8_t *) calloc(1, sizeof(uint8_t) * CHUNK_SIZE);
+
+  // Sets all blocks to a non-air type. (1)
+  for (int i = 0; i < CHUNK_SIZE; i++) {
+    new_chunk->blocks[i] = 1;
+  }
+
   new_chunk->x = x;
   new_chunk->z = z;
 
   return new_chunk;
 }
 
 void generate_chunk_mesh(chunk *render_chunk) {
-  GLfloat *buffer = malloc(sizeof(GLfloat) * (6 * 5 * 5) * CHUNK_SIZE);
+  GLfloat *buffer = malloc(sizeof(GLfloat) * (6 * 6 * 5) * CHUNK_SIZE);
   GLfloat *buffer_pointer = buffer;
-
-  for (int x = 0; x < CHUNK_WIDTH; x++) {
-    for (int z = 0; z < CHUNK_HEIGHT; z++) {
-      for (int y = 0; y < CHUNK_DEPTH; y++) {
-        uint32_t index = x + z + y;
-        uint8_t block = render_chunk->blocks[index];
-
-        create_cube_mesh(&buffer_pointer,
-          1, 1, 1, 0, 1, 1,
-          1, 1, 1, 1, 1, 1,
-          x, y, z, 0.5
-        );
-      }
-    }
+  int vertices_count = 0;
+
+  for (int i = 0; i < CHUNK_SIZE; i++) {
+    int x = i % CHUNK_X;
+    int z = (i / CHUNK_X) % CHUNK_Z;
+    int y = i / (CHUNK_X * CHUNK_Z);
+
+    uint8_t block = render_chunk->blocks[i];
+
+    // left(-x), right(+x), top(+y), bottom(-y), front(-z), back(+z)
+    uint8_t neighbors[6] = {1, 1, 1, 1, 1, 1};
+
+    // Calculate neighboring voxels and check if they are solid or not.
+    // If they are not solid, we should render a face. Otherwise, it is
+    // unnecessary to include the face. This resulting mesh will be
+    // contain only the exposed faces. Perf++.
+    //
+    // TODO(vy): Need to check between chunk boundaries for checking
+    // face exposure.
+    neighbors[0] = (x - 1 < 0) ? 1 : render_chunk->blocks[i - 1] == 0;
+    neighbors[1] = (x + 1 >= CHUNK_X) ? 1 : render_chunk->blocks[i + 1] == 0;
+    neighbors[2] = (y + 1 >= CHUNK_Y) ? 1 : render_chunk->blocks[i + (CHUNK_X * CHUNK_Z)] == 0;
+    neighbors[3] = (y - 1 < 0) ? 1 : render_chunk->blocks[i - (CHUNK_X * CHUNK_Z)] == 0;
+    neighbors[4] = (z - 1 < 0) ? 1 : render_chunk->blocks[i - CHUNK_X] == 0;
+    neighbors[5] = (z + 1 >= CHUNK_Z) ? 1 : render_chunk->blocks[i + CHUNK_X] == 0;
+
+    vertices_count += create_cube_mesh(&buffer_pointer,
+      neighbors[0], neighbors[1], neighbors[2], neighbors[3], neighbors[4], neighbors[5],
+      1, 1, 1, 1, 1, 1,
+      x, y, z, 0.5
+    );
   }
 
+
+  // Resize the mesh buffer to the actual size, since we allocated
+  // the largest size, but during mesh creation, we could have
+  // omitted faces, causing the buffer to be smaller than the
+  // maximum size.
+  buffer = realloc(buffer, (sizeof(GLfloat) * vertices_count * 5));
+
   // TODO(vy): Figure out how to calculate vertices of exposed faces:
   // 6 vertices per face * NUMBER OF FACES
   render_chunk->render_object = create_render_obj(
     GL_TRIANGLES,
     buffer,
-    (6 * 5 * 5) * CHUNK_SIZE,
-    (6 * 5) * CHUNK_SIZE
+    (6 * 6 * 5) * CHUNK_SIZE,
+    vertices_count
   );
 
   // Bind Vertices
@@ -69,9 +99,9 @@ void generate_chunk_mesh(chunk *render_chunk) {
   render_chunk->render_object->transform = m4_transpose(
     m4_translation(
       vec3(
-        render_chunk->x * CHUNK_WIDTH,
+        render_chunk->x * CHUNK_X,
         0,
-        render_chunk->z * CHUNK_HEIGHT
+        render_chunk->z * CHUNK_Z
       )
     )
   );
@@ -91,13 +121,15 @@ void generate_chunk_mesh(chunk *render_chunk) {
 // vertices, normals, uvs of ONLY the exposed faces. This impacts
 // mem space on the overall mesh significantly.
 
-void create_cube_mesh(
+int create_cube_mesh(
     GLfloat **data_pointer,
     int left, int right, int top, int bottom, int front, int back,
     int wleft, int wright, int wtop, int wbottom, int wfront, int wback,
     GLfloat x, GLfloat y, GLfloat z, GLfloat cube_size
   ) {
 
+  int vertices_count = 0;
+
   static const GLfloat vertices[6][4][3] = {
     {{-1, -1, -1}, {-1, -1, +1}, {-1, +1, -1}, {-1, +1, +1}},
     {{+1, -1, -1}, {+1, -1, +1}, {+1, +1, -1}, {+1, +1, +1}},
@@ -163,8 +195,11 @@ void create_cube_mesh(
       *((*data_pointer)++) = z + cube_size * vertices[i][j][2];
       *((*data_pointer)++) = (uvs[i][j][0] ? b : a);
       *((*data_pointer)++) = (uvs[i][j][1] ? b : a);
+      vertices_count++;
     }
   }
+
+  return vertices_count;
 }
 
 uint8_t block_from_index(chunk *render_chunk, uint32_t index) {
@@ -178,9 +213,9 @@ uint32_t index_from_block(uint16_t x, uint16_t y, uint16_t z) {
 
   // return (modz * SIZEXY) + (modx * SIZEY) + mody;
 
-  uint32_t x_length = CHUNK_WIDTH;
-  uint32_t z_length = CHUNK_HEIGHT;
-  uint32_t y_length = CHUNK_DEPTH;
+  uint32_t x_length = CHUNK_X;
+  uint32_t z_length = CHUNK_Z;
+  uint32_t y_length = CHUNK_Y;
   if (x > x_length) x = x_length;
   if (y > y_length) y = y_length;
   if (z > z_length) z = z_length;

src/chunk.h

@@ -4,10 +4,10 @@
 #include "third-party/math_3d.h"
 #include "gl.h"
 
-#define CHUNK_WIDTH 16
-#define CHUNK_HEIGHT 16
-#define CHUNK_DEPTH 256
-#define CHUNK_SIZE CHUNK_WIDTH * CHUNK_HEIGHT * CHUNK_DEPTH
+#define CHUNK_X 16
+#define CHUNK_Z 16
+#define CHUNK_Y 256
+#define CHUNK_SIZE CHUNK_X * CHUNK_Z * CHUNK_Y
 #define LOADED_CHUNK_BOUNDARY 3
 
 typedef struct {
@@ -23,7 +23,7 @@ typedef struct {
 
 chunk *create_chunk(GLfloat x, GLfloat z);
 void generate_chunk_mesh(chunk *render_chunk);
-void create_cube_mesh(
+int create_cube_mesh(
     GLfloat **data_pointer,
     int left, int right, int top, int bottom, int front, int back,
     int wleft, int wright, int wtop, int wbottom, int wfront, int wback,