[英]Instantiation order changing draw in OpenGL using VAO
I trying to use VAOs, VBOs and IBOs to draw a bunch of sphere over a plane. 我试图使用VAO,VBO和IBO在飞机上绘制一堆球体。 Before using these, everything was drawn as expected. 在使用它们之前,一切都按预期绘制。 After I started to use those, things got weird. 在我开始使用它们之后,事情变得很奇怪。 I can't post my whole code here because I have 5 classes (but if necessary I can provide a link to my code), so I'll try to post what I think it's useful. 我不能在这里发布整个代码,因为我有5个类(但是如果需要,我可以提供指向我的代码的链接),所以我将尝试发布我认为有用的内容。
With this class I can draw a sphere: 通过本课程,我可以画一个球体:
SphereShaderProgram::SphereShaderProgram(std::string vertexShaderPath, std::string fragmentShaderPath) : ProgramManager(vertexShaderPath, fragmentShaderPath)
{
_sphereH = 20;
_sphereW = 20;
_vbo = 0;
_vao = 0;
_ibo = 0;
CreateProgram();
BuildSphere();
BuildVAO();
}
SphereShaderProgram::~SphereShaderProgram()
{
glDeleteVertexArrays(1, &_vao);
glDeleteBuffers(1, &_vbo);
glDeleteBuffers(1, &_ibo);
}
void SphereShaderProgram::DrawSphere(const glm::mat4 &Projection, const glm::mat4 &ModelView)
{
_ModelViewProjection = Projection * ModelView;
_ModelView = ModelView;
Bind(); //glUseProgram
glBindVertexArray(_vao);
LoadVariables();
glDrawElements(GL_TRIANGLES, _sphereIndexes.size(), GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
UnBind();
}
int SphereShaderProgram::Get1DIndex(int line, int column)
{
return line * (int) _sphereH + column;
}
void SphereShaderProgram::BuildSphere()
{
for (int l = 0; l < _sphereH - 1; l++)
{
for (int c = 0; c < _sphereW - 1; c++)
{
int v1_1 = Get1DIndex(l, c);
int v2_1 = Get1DIndex(l + 1, c + 1);
int v3_1 = Get1DIndex(l + 1, c);
int v1_2 = Get1DIndex(l, c);
int v2_2 = Get1DIndex(l, c + 1);
int v3_2 = Get1DIndex(l + 1, c + 1);
_sphereIndexes.push_back(v1_1);
_sphereIndexes.push_back(v2_1);
_sphereIndexes.push_back(v3_1);
_sphereIndexes.push_back(v1_2);
_sphereIndexes.push_back(v2_2);
_sphereIndexes.push_back(v3_2);
}
}
for (int l = 0; l < _sphereH; l++)
{
for (int c = 0; c < _sphereW; c++)
{
float theta = ((float) l / (_sphereH - 1)) * (float) PI;
float phi = ((float) c / (_sphereW - 1)) * 2 * (float) PI;
float x = sin(theta) * cos(phi);
float z = sin(theta) * sin(phi);
float y = cos(theta);
_sphereCoordinates.push_back(x);
_sphereCoordinates.push_back(y);
_sphereCoordinates.push_back(z);
}
}
}
void SphereShaderProgram::BuildVAO()
{
// Generate and bind the vertex array object
glGenVertexArrays(1, &_vao);
glBindVertexArray(_vao);
// Generate and bind the vertex buffer object
glGenBuffers(1, &_vbo);
glBindBuffer(GL_ARRAY_BUFFER, _vbo);
glBufferData(GL_ARRAY_BUFFER, _sphereCoordinates.size() * sizeof(float), &_sphereCoordinates[0], GL_STATIC_DRAW);
// Generate and bind the index buffer object
glGenBuffers(1, &_ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, _sphereIndexes.size() * sizeof(unsigned int), &_sphereIndexes[0], GL_STATIC_DRAW);
glBindVertexArray(0);
}
void SphereShaderProgram::LoadUniformVariables()
{
glm::mat4 MVP = _ModelViewProjection;
glm::mat4 MV = _ModelView;
glm::mat3 N = glm::transpose(glm::inverse(glm::mat3(MV)));
glm::vec4 AC = glm::vec4(0.2, 0.2, 0.2, 1.0);
glm::vec4 DC = glm::vec4(0.7, 0.0, 0.0, 1.0);
glm::vec4 SC = glm::vec4(0.1, 0.1, 0.1, 1.0);
glm::vec3 LP = glm::vec3(1.0, 6.0, 4.0);
// OpenGL Matrices
GLuint ModelViewProjection_location = glGetUniformLocation(GetProgramID(), "mvpMatrix");
glUniformMatrix4fv(ModelViewProjection_location, 1, GL_FALSE, glm::value_ptr(MVP));
GLuint ModelView_location = glGetUniformLocation(GetProgramID(), "mvMatrix");
glUniformMatrix4fv(ModelView_location, 1, GL_FALSE, glm::value_ptr(MV));
GLuint Normal_location = glGetUniformLocation(GetProgramID(), "normalMatrix");
glUniformMatrix3fv(Normal_location, 1, GL_FALSE, glm::value_ptr(N));
// Lighting
GLuint AmbientColor_location = glGetUniformLocation(GetProgramID(), "ambientColor");
glUniform4fv(AmbientColor_location, 1, glm::value_ptr(AC));
GLuint DiffuseColor_location = glGetUniformLocation(GetProgramID(), "diffuseColor");
glUniform4fv(DiffuseColor_location, 1, glm::value_ptr(DC));
GLuint SpecularColor_location = glGetUniformLocation(GetProgramID(), "specularColor");
glUniform4fv(SpecularColor_location, 1, glm::value_ptr(SC));
GLuint LightPosition_location = glGetUniformLocation(GetProgramID(), "vLightPosition");
glUniform3fv(LightPosition_location, 1, glm::value_ptr(LP));
}
void SphereShaderProgram::LoadAtributeVariables()
{
// Vertex Attributes
GLuint VertexPosition_location = glGetAttribLocation(GetProgramID(), "vPosition");
glEnableVertexAttribArray(VertexPosition_location);
glVertexAttribPointer(VertexPosition_location, 3, GL_FLOAT, GL_FALSE, 0, 0);
}
void SphereShaderProgram::LoadVariables()
{
LoadUniformVariables();
LoadAtributeVariables();
}
And with that, a plane: 然后,飞机:
PlaneShaderProgram::PlaneShaderProgram(std::string vertexShaderPath, std::string fragmentShaderPath) : ProgramManager(vertexShaderPath, fragmentShaderPath)
{
CreateProgram();
_vbo = 0;
_vao = 0;
_ibo = 0;
BuildPlane();
BuildVAO();
}
PlaneShaderProgram::~PlaneShaderProgram()
{
glDeleteVertexArrays(1, &_vao);
glDeleteBuffers(1, &_vbo);
glDeleteBuffers(1, &_ibo);
}
void PlaneShaderProgram::DrawPlane(const glm::mat4 &Projection, const glm::mat4 &ModelView)
{
_ModelViewProjection = Projection * ModelView;
_ModelView = ModelView;
Bind();
glBindVertexArray(_vao);
LoadVariables();
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
UnBind();
}
void PlaneShaderProgram::BuildPlane()
{
_coordinates[0] = -1.0f;
_coordinates[1] = 0.0f;
_coordinates[2] = -1.0f;
_coordinates[3] = -1.0f;
_coordinates[4] = 0.0f;
_coordinates[5] = 1.0f;
_coordinates[6] = 1.0f;
_coordinates[7] = 0.0f;
_coordinates[8] = 1.0f;
_coordinates[9] = 1.0f;
_coordinates[10] = 0.0f;
_coordinates[11] = -1.0f;
_indexes[0] = 0;
_indexes[1] = 1;
_indexes[2] = 2;
_indexes[3] = 0;
_indexes[4] = 2;
_indexes[5] = 3;
}
void PlaneShaderProgram::BuildVAO()
{
// Generate and bind the vertex array object
glGenVertexArrays(1, &_vao);
glBindVertexArray(_vao);
// Generate and bind the vertex buffer object
glGenBuffers(1, &_vbo);
glBindBuffer(GL_ARRAY_BUFFER, _vbo);
glBufferData(GL_ARRAY_BUFFER, 12 * sizeof(GLfloat), _coordinates, GL_STATIC_DRAW);
// Generate and bind the index buffer object
glGenBuffers(1, &_ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6 * sizeof(GLuint), _indexes, GL_STATIC_DRAW);
glBindVertexArray(0);
}
void PlaneShaderProgram::LoadUniformVariables()
{
// OpenGL Matrices
GLuint ModelViewProjection_location = glGetUniformLocation(GetProgramID(), "mvpMatrix");
glUniformMatrix4fv(ModelViewProjection_location, 1, GL_FALSE, glm::value_ptr(_ModelViewProjection));
}
void PlaneShaderProgram::LoadAtributeVariables()
{
// Vertex Attributes
GLuint VertexPosition_location = glGetAttribLocation(GetProgramID(), "vPosition");
glEnableVertexAttribArray(VertexPosition_location);
glVertexAttribPointer(VertexPosition_location, 3, GL_FLOAT, GL_FALSE, 0, 0);
}
void PlaneShaderProgram::LoadVariables()
{
LoadUniformVariables();
LoadAtributeVariables();
}
This, on the other hand, is my main: 另一方面,这是我的主要目标:
int main(void)
{
// Set the error callback
glfwSetErrorCallback(ErrorCallback);
// Initialize GLFW
if (!glfwInit())
{
printf("Error initializing GLFW!\n");
exit(EXIT_FAILURE);
}
// Set the GLFW window creation hints - these are optional
glfwWindowHint(GLFW_SAMPLES, 4);
// Create a window and create its OpenGL context
GLFWwindow* window = glfwCreateWindow(width, height, "OpenGL 4 Base", NULL, NULL);
// If the window couldn't be created
if (!window)
{
fprintf(stderr, "Failed to open GLFW window.\n");
glfwTerminate();
exit(EXIT_FAILURE);
}
// Sets the context of the specified window on the calling thread
glfwMakeContextCurrent(window);
// Initialize GLEW
glewExperimental = true;
GLenum glewError = glewInit();
if (glewError != GLEW_OK)
{
printf("Error initializing GLEW! %s\n", glewGetErrorString(glewError));
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwSetKeyCallback(window, KeyCallback);
glfwSetWindowSizeCallback(window, WindowSizeCallback);
glfwSetScrollCallback(window, ScrollCallback);
// Set the view matrix
glm::mat4 ModelView = glm::lookAt(glm::vec3(0.0f, 7.0f, 15.0f), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f));
// Init matrix stack
glm_ModelViewMatrix.push(ModelView);
PlaneShaderProgram PlaneShaderProgram("FloorVertexShader.txt", "FloorFragShader.txt");
SphereShaderProgram SphereShaderProgram("ADSPerVertexVertexShader.txt", "ADSPerVertexFragShader.txt");
//SphereShaderProgram SphereShaderProgram = SphereShaderProgram("ADSPerPixelVertexShader.txt", "ADSPerPixelFragShader.txt");
// Set a background color
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
// 3D objects
glEnable(GL_DEPTH_TEST);
float d = 2.0f;
float p0 = -10.0f + d / 2;
// Main Loop
while (!glfwWindowShouldClose(window))
{
// Clear color buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Clone current modelview matrix, which can now be modified
glm_ModelViewMatrix.push(glm_ModelViewMatrix.top());
{
//------- ModelView Transformations
// Zoom in/out
glm_ModelViewMatrix.top() = glm::translate(glm_ModelViewMatrix.top(), glm::vec3(0.0, 0.0, zoom));
// Rotation
glm_ModelViewMatrix.top() = glm::rotate(glm_ModelViewMatrix.top(), beta, glm::vec3(1.0, 0.0, 0.0));
glm_ModelViewMatrix.top() = glm::rotate(glm_ModelViewMatrix.top(), alpha, glm::vec3(0.0, 0.0, 1.0));
//------- Draw the plane
glm_ModelViewMatrix.push(glm_ModelViewMatrix.top());
{
glm_ModelViewMatrix.top() = glm::scale(glm_ModelViewMatrix.top(), glm::vec3(7.0f, 1.0f, 7.0f));
PlaneShaderProgram.DrawPlane(Projection, glm_ModelViewMatrix.top());
}
glm_ModelViewMatrix.pop();
//------- Draw spheres
for (int i = 0; i < 10; i++)
{
for (int j = 0; j < 10; j++)
{
glm_ModelViewMatrix.push(glm_ModelViewMatrix.top());
{
glm_ModelViewMatrix.top() = glm::scale(glm_ModelViewMatrix.top(), glm::vec3(0.5f, 0.5f, 0.5f));
glm_ModelViewMatrix.top() = glm::translate(glm_ModelViewMatrix.top(), glm::vec3(p0 + i * d, 1.0f, p0 + j * d));
SphereShaderProgram.DrawSphere(Projection, glm_ModelViewMatrix.top());
}
glm_ModelViewMatrix.pop();
}
}
}
glm_ModelViewMatrix.pop();
// Swap buffers
glfwSwapBuffers(window);
// Get and organize events, like keyboard and mouse input, window resizing, etc...
glfwPollEvents();
}
// Close OpenGL window and terminate GLFW
glfwDestroyWindow(window);
// Finalize and clean up GLFW
glfwTerminate();
exit(EXIT_SUCCESS);
}
Instantiating the plane and then the sphere program, I get the following result (no plane at all): 实例化平面,然后实例化球体程序,我得到以下结果(根本没有平面):
Changing the order, that is the result: 更改顺序,结果是:
I'm trying to find a clue about what I'm missing, because I don't have any idea about what is wrong. 我正在尝试寻找有关我所缺少的内容的线索,因为我对错误之处一无所知。 Before using VAOs (just using glVertexAttribPointer
and glDrawElements
), everything was drawn correctly. 在使用VAO之前(仅使用glVertexAttribPointer
和glDrawElements
),一切glDrawElements
正确绘制。
Thank you in advance. 先感谢您。
The problem is with the placement of the glVertexAttribPointer()
call. 问题在于glVertexAttribPointer()
调用的位置。 You're calling it in the LoadAtributeVariables()
method, which in turn is called from the Draw*()
method. 您在LoadAtributeVariables()
方法中调用它,该方法又从Draw*()
方法中调用。
This should really be part of the VAO setup, for a couple of reasons: 出于以下两个原因,这实际上应该是VAO设置的一部分:
glVertexAttribPointer()
sets up the attribute to pull data from the currently bound VBO, ie the buffer bound as GL_ARRAY_BUFFER
. glVertexAttribPointer()
设置属性以从当前绑定的 VBO中提取数据,即绑定为GL_ARRAY_BUFFER
的缓冲区。 The first problem is only a performance issue. 第一个问题只是性能问题。 The second is the reason why your code does not work, since you do not have the correct VBO bound when glVertexAttribPointer()
is called. 第二个原因是您的代码无法正常工作的原因,因为在调用glVertexAttribPointer()
时您没有正确的VBO绑定。
To fix this, you only need to move the LoadAtributeVariables()
call into BuildVAO()
, at this location: 要解决此问题,您只需要将LoadAtributeVariables()
调用移至BuildVAO()
,在以下位置:
// Generate and bind the vertex buffer object
glGenBuffers(1, &_vbo);
glBindBuffer(GL_ARRAY_BUFFER, _vbo);
glBufferData(GL_ARRAY_BUFFER, _sphereCoordinates.size() * sizeof(float), &_sphereCoordinates[0], GL_STATIC_DRAW);
LoadAtributeVariables();
and remove it from where it currently is, so that it is not called before each draw call anymore. 并将其从当前位置删除,以便不再在每次绘制调用之前调用它。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.