无法获取分配给 OpenGL 中属性的 ID
Can't get ids assigned to an attribute in OpenGL
我试图让OpenGL自动为glsl属性分配一个ID，但失败了。
我的主要程序：
#include <iostream>
#include <GL/glew.h>
#include <GL/glfw3.h>
#include "test.h"
#include "shader_utils.h"
static void error_callback(int error, const char* description) {
std::cout << description << std::endl;
}
static void key_callback(GLFWwindow* window, int a, int b) {
if (a == GLFW_KEY_ESCAPE && b == GLFW_PRESS) {
glfwSetWindowShouldClose(window, GL_TRUE);
}
}
void test()
{
std::cout << "Starting up" << std::endl;
init();
run();
}
GLFWwindow *window;
GLuint shaders;
GLuint vertexBuffer;
int init() {
glfwSetErrorCallback(error_callback);
if(!glfwInit()) {
return -1;
}
window = glfwCreateWindow(640, 480, "GLFW test", NULL, NULL);
if (!window) {
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, key_callback);
glewExperimental = true;
glewInit();
shaders = LoadShaders("vertex.glsl", "fragment.glsl");
GLuint vao_id;
glGenVertexArrays(1, &vao_id);
glBindVertexArray(vao_id);
static const GLfloat vertex_data[] = {
// Bottom
-.5f, -.5f, -.5f, 1.f, 0.f, 0.f,
-.5f, -.5f, .5f, 1.f, 0.f, 0.f,
.5f, -.5f, .5f, 1.f, 0.f, 0.f,
};
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertex_data), vertex_data, GL_STATIC_DRAW);
}
void checkE() {
std::cout << "Checking for errors: ";
int err;
int a = 0;
while((err = glGetError()) != GL_NO_ERROR) {
std::cout << "Error: " << err << std::endl;
a = 1;
}
if(a == 0) {
std::cout << "no errors" << std::endl;
}
std::cout.flush();
}
int run() {
GLfloat angle = 0;
while(!glfwWindowShouldClose(window)) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(shaders);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
GLuint attrLocation = glGetAttribLocation(shaders, "location");
GLuint attrColor = glGetAttribLocation(shaders, "color");
std::cout << "AttribLocation('location'): ";
std::cout << glGetAttribLocation(shaders, "location") << std::endl;
std::cout << "AttribLocation('color'): ";
std::cout << glGetAttribLocation(shaders, "color") << std::endl;
checkE();
std::cout << std::endl;
std::cout << "glEnableVertexAttribArray()" << std::endl;
glEnableVertexAttribArray(attrLocation);
glEnableVertexAttribArray(attrColor);
checkE();
std::cout << std::endl;
std::cout << "glVertexAttribPointer();" << std::endl;
glVertexAttribPointer(
glGetAttribLocation(shaders, "location"), // Attribute
3, // Size
GL_FLOAT, // Size
GL_FALSE, // Normalized
24, // Stride
(GLvoid*) 0 // Offset
);
checkE();
std::cout << std::endl;
std::cout << "glVertexAttribPointer();" << std::endl;
glVertexAttribPointer(
glGetAttribLocation(shaders, "color"),
3,
GL_FLOAT,
GL_FALSE,
24,
(GLvoid*) (3*sizeof(GLfloat))
);
checkE();
std::cout << std::endl;
glDrawArrays(GL_TRIANGLES, 0, 3);
checkE();
std::cout << std::endl;
glDisableVertexAttribArray(attrLocation);
glDisableVertexAttribArray(attrColor);
checkE();
std::cout << std::endl;
glfwSwapBuffers(window);
glfwPollEvents();
glfwSetWindowShouldClose(window, GL_TRUE);
}
glfwDestroyWindow(window);
glfwTerminate();
}
程序输出：
Starting up
Compiling shader : vertex.glsl
Compiling shader : fragment.glsl
Linking program
AttribLocation('location'): -1
AttribLocation('color'): -1
Checking for errors: no errors
glEnableVertexAttribArray()
Checking for errors: Error: 1281
glVertexAttribPointer();
Checking for errors: Error: 1281
glVertexAttribPointer();
Checking for errors: Error: 1281
Checking for errors: no errors
Checking for errors: Error: 1281
着色器加载程序：
#include "shader_utils.h"
#include <string>
#include <iostream>
#include <fstream>
#include <vector>
#include "GL/glew.h"
#include "GL/glfw3.h"
GLuint LoadShaders(const char * vertex_file_path, const char * fragment_file_path){
// Create the shaders
GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
// Read the Vertex Shader code from the file
std::string VertexShaderCode;
std::ifstream VertexShaderStream(vertex_file_path, std::ios::in);
if(VertexShaderStream.is_open())
{
std::string Line = "";
while(getline(VertexShaderStream, Line))
VertexShaderCode += "n" + Line;
VertexShaderStream.close();
} else {
std::cout << "could not openn";
}
// Read the Fragment Shader code from the file
std::string FragmentShaderCode;
std::ifstream FragmentShaderStream(fragment_file_path, std::ios::in);
if(FragmentShaderStream.is_open()){
std::string Line = "";
while(getline(FragmentShaderStream, Line))
FragmentShaderCode += "n" + Line;
FragmentShaderStream.close();
}
GLint Result = GL_FALSE;
int InfoLogLength;
// Compile Vertex Shader
printf("Compiling shader : %sn", vertex_file_path);
char const * VertexSourcePointer = VertexShaderCode.c_str();
glShaderSource(VertexShaderID, 1, &VertexSourcePointer , NULL);
glCompileShader(VertexShaderID);
// Check Vertex Shader
glGetShaderiv(VertexShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(VertexShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
std::vector<char> VertexShaderErrorMessage(InfoLogLength);
glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
fprintf(stdout, "%sn", &VertexShaderErrorMessage[0]);
// Compile Fragment Shader
printf("Compiling shader : %sn", fragment_file_path);
char const * FragmentSourcePointer = FragmentShaderCode.c_str();
glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer , NULL);
glCompileShader(FragmentShaderID);
// Check Fragment Shader
glGetShaderiv(FragmentShaderID, GL_COMPILE_STATUS, &Result);
glGetShaderiv(FragmentShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
std::vector<char> FragmentShaderErrorMessage(InfoLogLength);
glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
fprintf(stdout, "%sn", &FragmentShaderErrorMessage[0]);
// Link the program
fprintf(stdout, "Linking programn");
GLuint ProgramID = glCreateProgram();
glAttachShader(ProgramID, VertexShaderID);
glAttachShader(ProgramID, FragmentShaderID);
glLinkProgram(ProgramID);
// Check the program
glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
std::vector<char> ProgramErrorMessage( std::max(InfoLogLength, int(1)) );
glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
fprintf(stdout, "%sn", &ProgramErrorMessage[0]);
glDeleteShader(VertexShaderID);
glDeleteShader(FragmentShaderID);
std::cout.flush();
return ProgramID;
}
顶点着色器：
#version 130
in vec4 position;
in vec3 color;
out vec3 f_color;
void main() {
f_color = color;
gl_Position = position * gl_ModelViewProjectionMatrix;
}
片段着色器：
#version 130
in vec3 color;
void main() {
gl_FragColor = vec4(color, 1);
}
出于某种原因，我只得到-1作为两个属性的位置。显然，其余的错误是由无效的位置索引引起的？
来自OpenGL文档：If the named attribute variable is not an active attribute in the specified program object or if name starts with the reserved prefix "gl_", a value of -1 is returned.
这些名称不是以gl_开头的，它们在着色器中使用，所以我不应该得到-1的值。我错过了什么？
您无法获取color的属性位置，因为它不是活动的。虽然在本例中确实使用了color来计算f_color，但片段着色器不使用f_color，因此链接器确定名为：color的顶点属性处于非活动状态。
解决方案非常简单，真的：
片段着色器：
#version 130
in vec3 f_color; // RENAMED from color, so that this matches the output from the VS.
void main() {
gl_FragColor = vec4(f_color, 1);
}
在"顶点着色器"（输入顶点属性）和"片段着色器"（输入不同）阶段中，将名称color重复用于不同目的并非错误，因此编译器/链接器不会抱怨。但是，如果尝试执行类似inout color的操作，则会出现错误，因此，必须使用不同名称的variation将顶点属性传递给几何体/镶嵌/片段着色器。如果阶段之间的输入/输出名称不匹配，则原始顶点属性很可能被视为不活动。
此外，除非您正在转换ModelViewProjection矩阵，否则顶点着色器中的矩阵乘法是向后的。OpenGL使用的列主矩阵乘法应该从右向左读取。也就是说，从对象空间位置（最右边）开始，变换到剪辑空间（最左边）。
换句话说，这是变换顶点的正确方法。。。
gl_Position = gl_ModelViewProjectionMatrix * position;
~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~
clip space object space to clip space obj space
相关文章：
- 如何导出包含具有"std::unique_ptr"值的"std::map"属性的
- C++概念：如何使用'concept'检查模板化结构的属性？
- 子目录是否继承属性，例如add_definitions，include_directories和父Cmakelist.t
- 通过指向指针数组的指针访问子类的属性
- MSVC是否支持C++11样式的属性而不是__declspec
- QML:修改在不同QML文件(而非main.QML）中定义的子对象的属性
- 类的C++属性似乎已重新初始化
- 从函数角度看ID到文件路径的内部与外部映射
- 通过组合不同的类型来创建唯一的id
- 我不断收到 [错误] ID 返回 1 退出状态错误，但看不到问题所在
- Qt Quick-如何仅从c++代码与qml属性交互
- FFMPEG配置文件级别id大小无效
- 用概念检查属性的类型
- 方法内部但循环仍得到预期的不合格id错误C++
- 如何使用 API 获取 QML 对象的 id 属性C++
- 具有可移动节点、可访问属性和可靠ID的C++图
- 无法获取分配给 OpenGL 中属性的 ID
- C++:父对象在不调用方法的情况下更改其id属性
- 如何为自定义BLE特性添加名称和ID属性
- 对于具有额外"通道"和"id"属性的多线程应用使用 boost：：log 的最佳方法
