[英]Sphere mesh in modern OpenGL
我正在嘗試創建一個球體表面的三角形網格並使用 OpenGL 4.1 繪制它。
這是我目前使用的代碼,從該問題的第二個答案中獲得,頂點布局是 [x, y, z, r, b, g, a] 這就是為什么每個頂點有 7 個浮點數:
std::vector<float> vertices;
std::vector<unsigned int> indices;
const float dLambda = 2 * glm::pi<float>() / meridianNumber;
const float dPhi = glm::pi<float>() / parallelNumber;
unsigned int lastVertex = 0;
for (int i = 0; i < parallelNumber; ++i) {
for (int j = 0; j < meridianNumber; ++j) {
std::cout << "lot: " << glm::degrees(j * dLambda);
std::cout << "\tlat: " << glm::degrees(i * dPhi);
std::cout << std::endl;
float lambda1 = j * dLambda;
float phi1 = i * dPhi;
float lambda2 = j+1 == parallelNumber ? 2 * glm::pi<float>()
: (j+1) * dLambda;
float phi2 = i+1 == meridianNumber ? glm::pi<float>()
: (i+1) * dPhi;
// vertex 1
vertices.emplace_back(cosf(lambda1) * sinf(phi1) * radius);
vertices.emplace_back(cosf(phi1) * radius);
vertices.emplace_back(sinf(lambda1) * sinf(phi1) * radius);
vertices.emplace_back(0.5f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
// vertex 2
vertices.emplace_back(cosf(lambda1) * sinf(phi2) * radius);
vertices.emplace_back(cosf(phi2) * radius);
vertices.emplace_back(sinf(lambda1) * sinf(phi2) * radius);
vertices.emplace_back(0.5f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
// vertex 3
vertices.emplace_back(cosf(lambda2) * sinf(phi1) * radius);
vertices.emplace_back(cosf(phi1) * radius);
vertices.emplace_back(sinf(lambda2) * sinf(phi1) * radius);
vertices.emplace_back(0.5f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
// vertex 4
vertices.emplace_back(cosf(lambda2) * sinf(phi2) * radius);
vertices.emplace_back(cosf(phi2) * radius);
vertices.emplace_back(sinf(lambda2) * sinf(phi2) * radius);
vertices.emplace_back(0.5f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
vertices.emplace_back(1.0f);
indices.emplace_back(lastVertex);
indices.emplace_back(lastVertex+1);
indices.emplace_back(lastVertex+2);
indices.emplace_back(lastVertex+1);
indices.emplace_back(lastVertex+3);
indices.emplace_back(lastVertex+2);
lastVertex += 4;
}
我用來繪制的代碼是:
GLCall(glDrawElements(
GL_TRIANGLES,
indicesNumber,
GL_UNSIGNED_INT,
(const void*) 0
));
編輯 1: VAO 設置非常復雜,因為我在 opengl 上寫了一點抽象層……我有一個名為 VertexBuffer 的類,它可以創建、保持活動並銷毀 OpenGL 數組緩沖區。 另一個類 IndexBuffer 與前一個管理 Element 數組緩沖區的類非常相似。 這兩個類使用起來非常簡單,它們可以被構造、綁定、解除綁定和銷毀,僅此而已。 還有第三個類表示 OpenGL 頂點緩沖區中單個頂點的布局; 這個名為 VertexLayout 的類包含調用 glVertexAttribPointer 所需的所有數據。
馬力:
class VertexLayout {
private:
struct Element {
unsigned int type;
unsigned int count;
unsigned char normalized;
size_t typeSize;
Element(
unsigned int type, unsigned int count, unsigned char normalized,
size_t typeSize
);
};
std::vector<Element> elements;
unsigned int stride;
public:
VertexLayout();
template<typename T>
VertexLayout &push(unsigned int count, unsigned char normalized = GL_FALSE){
std::fputs(
"this function has to be implemented for desired type",
stderr
);
assert(false);
return *this;
}
const std::vector<Element> &getElements() const;
unsigned int getStride() const;
};
cp:
template<>
VertexLayout &VertexLayout::push<unsigned int>(
unsigned int count, unsigned char normalized
) {
elements.emplace_back(
GL_UNSIGNED_INT, count, normalized, sizeof(unsigned int)
);
stride += count * sizeof(unsigned int);
return *this;
};
template<>
VertexLayout &VertexLayout::push<unsigned char>(
unsigned int count, unsigned char normalized
) {
elements.emplace_back(
GL_UNSIGNED_BYTE, count, normalized, sizeof(unsigned char)
);
stride += count * sizeof(unsigned char);
return *this;
};
template<>
VertexLayout &VertexLayout::push<float>(unsigned int count, unsigned char normalized){
elements.emplace_back(GL_FLOAT, count, normalized, sizeof(float));
stride += count * sizeof(float);
return *this;
}
VertexLayout::Element::Element(
unsigned int type, unsigned int count,
unsigned char normalized, size_t typeSize
) : type(type), count(count), normalized(normalized), typeSize(typeSize) {}
const std::vector<VertexLayout::Element> &VertexLayout::getElements() const {
return elements;
}
unsigned int VertexLayout::getStride() const {
return stride;
}
VertexLayout::VertexLayout() : stride(0) {}
因此,應該為每個 VertexBuffer 對象創建一個 VertexLayout 實例,並且應該將 foreach opengl 屬性稱為push<type>(numberOfElementOfThatType)
。
第四個也是最后一個類是表示 VAO 的 VertexArray 類:最后一個類跟蹤所有連接到 VAO 的 VertexBuffer 和 IndexBuffer 對象,並在使用以下方法添加 VertexBuffer 時設置調用 glVertexAttribPointer 的布局:
void VertexArray::addBuffer(
const VertexBuffer &buffer, const VertexLayout &layout
) {
GLCall(glBindVertexArray(id));
buffer.bind();
const auto &elements = layout.getElements();
size_t offset = 0;
for (unsigned int i = 0; i < elements.size(); ++i) {
const auto &element = elements[i];
GLCall(glEnableVertexAttribArray(i));
GLCall(glVertexAttribPointer(
i, element.count, element.type, element.normalized,
layout.getStride(), (const void *)offset
));
offset += element.count * element.typeSize;
}
vertexBuffers.emplace_back(buffer);
}
GLCall 是一個宏,它在發布時什么都不做,而在調試時清除 OpenGL 錯誤並打印新錯誤。
編輯 2:這是代表一個 VBO 的 VertexBuffer 類:
馬力
class VertexBuffer {
private: // static
static std::map<unsigned int, unsigned int> references;
private: // member
unsigned int rendererID;
public:
VertexBuffer();
VertexBuffer(
const void *data, unsigned long size,
unsigned int usage = GL_STATIC_DRAW
);
VertexBuffer(const VertexBuffer &oth);
VertexBuffer &operator=(const VertexBuffer &rhs);
~VertexBuffer();
void bind() const;
void unbind() const;
};
cp:
std::map<unsigned int, unsigned int> VertexBuffer::references;
VertexBuffer::VertexBuffer(
const void *data,
unsigned long size,
unsigned int usage
) {
GLCall(glGenBuffers(1, &rendererID));
GLCall(glBindBuffer(GL_ARRAY_BUFFER, rendererID));
GLCall(glBufferData(GL_ARRAY_BUFFER, size, data, usage));
references.insert_or_assign(rendererID, 1);
}
VertexBuffer::VertexBuffer(const VertexBuffer &oth) {
if (oth.rendererID != 0){
auto ref = references.find(oth.rendererID);
assert(ref != references.end());
ref->second++;
}
rendererID = oth.rendererID;
}
VertexBuffer &VertexBuffer::operator=(const VertexBuffer &rhs) {
if (rendererID != 0) {
auto refs = references.find(rendererID);
assert(refs != references.end());
if (--refs->second == 0) {
GLCall(glDeleteBuffers(1, &rendererID));
references.erase(refs);
}
}
if (rhs.rendererID != 0){
auto ref = references.find(rhs.rendererID);
assert(ref != references.end());
ref->second++;
}
rendererID = rhs.rendererID;
return *this;
}
VertexBuffer::VertexBuffer() : rendererID(0) {}
VertexBuffer::~VertexBuffer() {
if (rendererID != 0) {
auto ref = references.find(rendererID);
assert(ref != references.end());
if (--ref->second == 0) {
GLCall(glDeleteBuffers(1, &rendererID));
references.erase(ref);
}
}
}
void VertexBuffer::bind() const {
GLCall(glBindBuffer(GL_ARRAY_BUFFER, rendererID));
}
void VertexBuffer::unbind() const {
GLCall(glBindBuffer(GL_ARRAY_BUFFER, 0));
}
在球體中,我只有一個包含位置和顏色的大緩沖區。
我找到了解決方案。 這是一個非常愚蠢的錯誤:VertexBuffer 類的構造函數需要以字節為單位的緩沖區大小,但是當我調用它時,我只傳遞了 std::vector 的大小,即元素的數量。
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