Hey there! I get it—full-on optimal Greedy Meshing can feel like diving into a dense math textbook, but we can build a simplified version that still cuts down your draw calls significantly, and it’s totally approachable. Let’s walk through this step by step, focused on single-Chunk rendering first.

First: Prep Work - Figure Out Which Faces Are Visible #

Before merging faces, we need to know which ones actually need to be drawn. A face is visible if the adjacent block in that direction is either outside the Chunk, air, or transparent. Here’s a quick helper function to check that:

def is_face_visible(chunk, x, y, z, face):
    # Shift coordinates to check the adjacent block
    nx, ny, nz = x, y, z
    if face == "North":
        nx -= 1
    elif face == "East":
        nz += 1
    elif face == "South":
        nx += 1
    elif face == "West":
        nz -= 1
    elif face == "Top":
        ny += 1
    elif face == "Bottom":
        ny -= 1

    # Check if adjacent block is out of bounds, or is transparent/air
    if nx < 0 or nx >= CHUNK_SIZE or ny < 0 or ny >= CHUNK_SIZE or nz < 0 or nz >= CHUNK_SIZE:
        return True
    adjacent_block = chunk[nx][ny][nz]
    return adjacent_block.is_transparent()  # Assume your Block class has this method

Core Idea: Merge Faces in Axis-Aligned Groups #

Greedy Meshing works by merging adjacent, visible, identical faces into big rectangles. Instead of tackling all 6 faces at once, split them into 3 axis-aligned groups—this simplifies the logic a lot:

• Top/Bottom Faces (parallel to the X-Z plane)
• North/South Faces (parallel to the Y-Z plane)
• East/West Faces (parallel to the X-Y plane)

Let’s use Top Faces as an example to walk through the process.

Step 1: Mark Visible Top Faces #

Create a 2D array top_visible[x][z] where each entry is True if the top face of the block at (x, y, z) (y being the highest non-air block at that X-Z position) is visible.

Step 2: Merge Contiguous Visible Faces #

Here’s where the "greedy" part comes in, simplified:

1. Fix a Z coordinate, then iterate along the X axis. When you hit an unprocessed, visible top face, note the starting X (start_x).
2. Keep moving right along X until you hit a non-visible face, a different block type (since we can’t merge different textures), or the Chunk edge—this is your end_x.
3. Now, see how far you can extend this X range along the Z axis: check if every X position from start_x to end_x has a visible, matching top face at the next Z coordinate. Keep extending until this breaks.
4. Mark all positions in this merged rectangle as processed, so we don’t rework them.

Step 3: Generate Renderable Geometry #

For the merged rectangle, create the 4 vertices (or two triangles) that make up the big face, assign the correct texture coordinates, and add it to your render queue.

The logic for North/South and East/West faces is almost identical—you just swap which axes you iterate and extend along. For example, North Faces are parallel to Y-Z, so you’d fix X, iterate Y first, then extend Z.

Quick Optimizations (No Extra Complexity) #

• Only merge identical blocks: Don’t merge faces from different block types—you’ll end up with messed-up textures. Make sure to check that the block type matches when extending your rectangles.
• Skip processed faces: Use a 2D processed array for each face group to avoid reprocessing the same area multiple times.

Example Pseudocode for Merging Top Faces #

def merge_top_faces(chunk, chunk_world_x, chunk_world_z):
    CHUNK_SIZE = 16  # Adjust to your Chunk size
    processed = [[False for _ in range(CHUNK_SIZE)] for _ in range(CHUNK_SIZE)]
    render_queue = []

    for z in range(CHUNK_SIZE):
        for x in range(CHUNK_SIZE):
            if processed[x][z]:
                continue

            # Get the highest non-air block at this X-Z position
            y = get_highest_block_y(chunk, x, z)
            if y is None or not is_face_visible(chunk, x, y, z, "Top"):
                processed[x][z] = True
                continue
            current_block_type = chunk[x][y][z].block_type

            # Expand along X first
            end_x = x
            while end_x < CHUNK_SIZE and not processed[end_x][z]:
                check_y = get_highest_block_y(chunk, end_x, z)
                if (check_y != y 
                    or chunk[end_x][check_y][z].block_type != current_block_type
                    or not is_face_visible(chunk, end_x, check_y, z, "Top")):
                    break
                end_x += 1

            # Now expand along Z
            max_z = z
            valid_extension = True
            while max_z + 1 < CHUNK_SIZE and valid_extension:
                # Check if the entire X range is valid at the next Z
                for cx in range(x, end_x):
                    if processed[cx][max_z + 1]:
                        valid_extension = False
                        break
                    check_y = get_highest_block_y(chunk, cx, max_z + 1)
                    if (check_y != y 
                        or chunk[cx][check_y][max_z + 1].block_type != current_block_type
                        or not is_face_visible(chunk, cx, check_y, max_z + 1, "Top")):
                        valid_extension = False
                        break
                if valid_extension:
                    max_z += 1

            # Mark this entire rectangle as processed
            for cx in range(x, end_x):
                for cz in range(z, max_z + 1):
                    processed[cx][cz] = True

            # Generate world-space vertices for the merged top face
            world_x1 = chunk_world_x * CHUNK_SIZE + x
            world_z1 = chunk_world_z * CHUNK_SIZE + z
            world_x2 = chunk_world_x * CHUNK_SIZE + end_x
            world_z2 = chunk_world_z * CHUNK_SIZE + max_z + 1
            world_y = y + 1  # Top face sits at Y = block Y + 1

            # Add two triangles (to make a quad) to the render queue
            render_queue.append([
                (world_x1, world_y, world_z1),
                (world_x2, world_y, world_z1),
                (world_x1, world_y, world_z2)
            ])
            render_queue.append([
                (world_x2, world_y, world_z1),
                (world_x2, world_y, world_z2),
                (world_x1, world_y, world_z2)
            ])

    return render_queue

Start with implementing one face group (like Top/Bottom) first, test it to make sure merged faces render correctly, then add the other groups. This simplified version doesn’t use any advanced math, just nested loops and checks—perfect for getting your feet wet with Greedy Meshing.

内容的提问来源于stack exchange，提问作者Rob van Dijk