我正在使用 C++ 开发体素引擎，在实现了块之后，我意识到它们的生成成本真的很高。我的意思不是用块填充它们，我的意思是生成一个块网格。
生成块后，游戏运行顺畅，除了放置和删除体素。每当一个块发生变化时，它的网格就会被重建。这是昂贵的过程。处理一个块大约需要 0.36 秒，这会导致在编辑一个块时冻结大约 0.36 秒。此外，由于单个区块的 0.36 秒峰值，加载超过一个区块半径或 3 或 4 个区块的世界需要几分钟。有 4 个块，需要 189 秒，(4*2)^3*0.36（每个 0.36 秒 512 个块）
这是我的网格生成代码。它遍历块中的每个块，如果它不是空气，它会为其添加立方体顶点，否则，忽略它。稍后这将成为一个更复杂的方法，其中包含我计划的一些东西，如果该方法已经很慢，那就不好了。
void WorldRenderer::constructChunkMesh(Chunk* chunk)
{
if (!chunk->isInitialized() || chunk->getNumBlocks() <= 0)
return; //If the chunk isn't initialized, or is empty, don't construct anything for it.
ChunkMesh mesh;
//iterate over every block within the chunk.
//CHUNK_SIZE has a value of 16. Each chunk is 16x16x16 blocks.
for (int x = 0; x < CHUNK_SIZE; x++)
{
for (int y = 0; y < CHUNK_SIZE; y++)
{
for (int z = 0; z < CHUNK_SIZE; z++)
{
if (chunk->getBlock(x, y, z) != Blocks::BLOCK_TYPE_AIR) //if the block is solid, add vertices, otherwise, don't render it.
{
//the 8 vertices for a cube. mesh.addVertex(...) returns the index.
int i0 = mesh.addVertex(Vertex(glm::vec3(0.0F, 0.0F, 1.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i1 = mesh.addVertex(Vertex(glm::vec3(1.0F, 0.0F, 1.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i2 = mesh.addVertex(Vertex(glm::vec3(0.0F, 1.0F, 1.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i3 = mesh.addVertex(Vertex(glm::vec3(1.0F, 1.0F, 1.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i4 = mesh.addVertex(Vertex(glm::vec3(0.0F, 0.0F, 0.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i5 = mesh.addVertex(Vertex(glm::vec3(1.0F, 0.0F, 0.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i6 = mesh.addVertex(Vertex(glm::vec3(0.0F, 1.0F, 0.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
int i7 = mesh.addVertex(Vertex(glm::vec3(1.0F, 1.0F, 0.0F) + glm::vec3(x, y, z), glm::vec3(0.0F, 1.0F, 0.0F), glm::vec4(1.0F, 1.0F, 1.0F, 1.0F), glm::vec2(0.0F, 0.0F)));
//The xyz coord in the iteration in world-relative coordinates, instead of chunk-relative
int wx = (chunk->getPos().x * CHUNK_SIZE) + x;
int wy = (chunk->getPos().y * CHUNK_SIZE) + y;
int wz = (chunk->getPos().z * CHUNK_SIZE) + z;
//top y+
if (World::getBlock(wx, wy + 1, wz) <= 0)
{
//if a block does not exist in the y+ direction to this one, add the top face.
mesh.addFace(i2, i3, i7);
mesh.addFace(i2, i7, i6);
}
//bottom y-
if (World::getBlock(wx, wy - 1, wz) <= 0)
{
//if a block does not exist in the y- direction to this one, add the top face.
mesh.addFace(i0, i4, i1);
mesh.addFace(i1, i4, i5);
}
//front z-
if (World::getBlock(wx, wy, wz - 1) <= 0)
{
//if a block does not exist in the z- direction to this one, add the top face.
mesh.addFace(i6, i7, i4);
mesh.addFace(i7, i5, i4);
}
//back z+
if (World::getBlock(wx, wy, wz + 1) <= 0)
{
//if a block does not exist in the z+ direction to this one, add the top face.
mesh.addFace(i0, i1, i2);
mesh.addFace(i1, i3, i2);
}
//right x+
if (World::getBlock(wx + 1, wy, wz) <= 0)
{
//if a block does not exist in the x+ direction to this one, add the top face.
mesh.addFace(i1, i7, i3);
mesh.addFace(i1, i5, i7);
}
//left x-
if (World::getBlock(wx - 1, wy, wz) <= 0)
{
//if a block does not exist in the x- direction to this one, add the top face.
mesh.addFace(i2, i6, i4);
mesh.addFace(i0, i2, i4);
}
}
}
}
}
//The rest of this is OpenGL code, and doesn't add any significant
//performance drop. I have measured this.
GeometryData gd = MeshHandler::compileGeometry(mesh.vertices.data(), mesh.indices.data(), mesh.vertices.size(), mesh.indices.size());
RenderableChunk rc;
rc.pos = chunk->getPos();
auto a = std::find(chunks.begin(), chunks.end(), rc);
int index = a - chunks.begin();
if (a != chunks.end())
{
rc = chunks[index];
}
else
{
GLuint VAO;
GLuint* VBOs = new GLuint[2];
//1527864 bytes maximum per chunk (1.5MB)
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
glGenBuffers(2, VBOs);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * 8 * MAX_BLOCKS, nullptr, GL_DYNAMIC_DRAW);
glVertexAttribPointer(ATTRIB_VERTEX_ARRAY, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(offsetof(Vertex, position)));
glEnableVertexAttribArray(ATTRIB_VERTEX_ARRAY);
glVertexAttribPointer(ATTRIB_NORMAL_ARRAY, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(offsetof(Vertex, normal)));
glEnableVertexAttribArray(ATTRIB_NORMAL_ARRAY);
glVertexAttribPointer(ATTRIB_COLOUR_ARRAY, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(offsetof(Vertex, colour)));
glEnableVertexAttribArray(ATTRIB_COLOUR_ARRAY);
glVertexAttribPointer(ATTRIB_TEXTURE_ARRAY, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), BUFFER_OFFSET(offsetof(Vertex, texture)));
glEnableVertexAttribArray(ATTRIB_TEXTURE_ARRAY);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, VBOs[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLushort) * 36 * MAX_BLOCKS, nullptr, GL_DYNAMIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindVertexArray(0);
rc.VAO = VAO;
rc.VBOs = VBOs;
}
rc.numIndices = gd.numIndices;
glBindVertexArray(rc.VAO);
glBindBuffer(GL_ARRAY_BUFFER, rc.VBOs[0]);
glBufferSubData(GL_ARRAY_BUFFER, 0, gd.vboSize(), gd.vertices);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, rc.VBOs[1]);
glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, gd.iboSize(), gd.indices);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindVertexArray(0);
if (index >= 0 && index < chunks.size())
{
chunks[index] = rc;
}
else
{
chunks.push_back(rc);
}
}
使用的结构ChunkMesh，我认为问题在于：
struct ChunkMesh
{
std::vector<Vertex> vertices;
std::vector<GLushort> indices;
int addVertex(Vertex v)
{
//add a vertex to the mesh, and return its index in the list.
vertices.push_back(v);
return vertices.size() - 1;
}
void addFace(int v0, int v1, int v2)
{
//construct a face with 3 vertices.
indices.push_back(v0);
indices.push_back(v1);
indices.push_back(v2);
}
};
我相信问题出在 ChunkMesh 结构中，使用了 push_backs。数百个std::vectorpush_backs 非常慢，但我找不到替代方案。我可以用什么替换矢量？
我要完全错误地渲染这些块吗？如何优化此功能？
任何帮助将非常感激。
谢谢。
编辑： 我尝试保留向量，令我困惑的是，这对性能没有影响。它保持在 0.36 秒。
我添加了一个构造函数来ChunkMesh获取块的数量，如下所示：
ChunkMesh(int numBlocks)
{
vertices.reserve(numBlocks * 8); //8 vertices per cube
indices.reserve(numBlocks * 36); //36 indices per cube
}