我正在尝试创建一个可用作OpenGL测试工具的示例程序。我到目前为止似乎工作，但似乎忽略了通过统一变量MVPMatrix传递的MVP矩阵。当我添加代码来阅读统一后面并检查它是否实际正确更新时，我在执行此操作时出现无效操作错误，我无法理解为什么 - 发生了什么？
#include "stdafx.h"
#include <iostream>
#include <memory>
#include <sdl/SDL.h>
#include <assimp/Importer.hpp>
#include <assimp/mesh.h>
#include <assimp/scene.h>
#include <sdl/SDL_image.h>
#include <glm/glm.hpp>
#include <Windows.h>
#include <GL/glew.h>
#include <GL/GL.h>
#include <gl/GLU.h>
#include <vector>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <assimp/Importer.hpp>
#include <assimp/mesh.h>
#include <assimp/postprocess.h>
#include <assimp/vector3.h>
using namespace std;
void checkGLShaderStatus(GLuint id, GLuint thingToCheck, bool shader) {
GLint ret;
if (shader) glGetShaderiv(id, thingToCheck, &ret); else glGetProgramiv(id, thingToCheck, &ret);
// If there was an error
if (ret == GL_FALSE) {
// Print it out, then halt
GLint maxLength = 0;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &maxLength);
GLchar *shaderErrorLog = (GLchar*)malloc(sizeof(GLchar)*(maxLength + 1));
glGetShaderInfoLog(id, maxLength, &maxLength, shaderErrorLog);
shaderErrorLog[maxLength] = '\0';
cout << shaderErrorLog;
free(shaderErrorLog);
int junk;
cin >> junk;
exit(EXIT_FAILURE);
}
}
GLuint buildShader(const GLchar **source, GLuint length, GLenum type) {
// Create the shader
GLuint shaderId = glCreateShader(type);
// Upload source code
glShaderSource(shaderId, length, source, NULL);
// Compile the shader
glCompileShader(shaderId);
// See how the compilation went
checkGLShaderStatus(shaderId, GL_COMPILE_STATUS, true);
return shaderId;
}
void checkGL(string stage) {
GLuint error = glGetError();
if (error != GL_NO_ERROR) {
cout << "OpenGL broke..";
switch (error) {
case GL_INVALID_ENUM:
cout << "Invalid Enum";
break;
case GL_INVALID_VALUE:
cout << "Value out of range";
break;
case GL_INVALID_OPERATION:
cout << "Invalid operation";
break;
case GL_INVALID_FRAMEBUFFER_OPERATION:
cout << "Incomplete framebuffer";
break;
case GL_OUT_OF_MEMORY:
cout << "Out of memory";
break;
default:
cout << "Oh boy, did it break..";
}
cout << " (" << stage << ")" << endl;
int junk;
cin >> junk;
exit(EXIT_FAILURE);
}
}
int _tmain(int argc, _TCHAR* argv[])
{
if (SDL_Init(SDL_INIT_EVERYTHING) == -1) exit(EXIT_FAILURE);
if (IMG_Init(IMG_INIT_JPG | IMG_INIT_PNG) == -1) exit(EXIT_FAILURE);
Assimp::Importer importer;
const aiScene *importedScene = importer.ReadFile("Table.3ds",aiProcess_Triangulate);
if (importedScene == nullptr) exit(EXIT_FAILURE);
aiMesh *theMesh = importedScene->mMeshes[0];
if (theMesh == nullptr) exit(EXIT_FAILURE);
cout << "I imported a mesh with " << theMesh->mNumVertices << " vertices and " << theMesh->mNumFaces << " faces! " << endl;
SDL_Window *win = nullptr;
win = SDL_CreateWindow("My even more awesome SDL/OGL program", 100, 100, 640, 480, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
if (win == nullptr) exit(EXIT_FAILURE);
SDL_Renderer *ren = nullptr;
ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
if (ren == nullptr) exit(EXIT_FAILURE);
SDL_GLContext context = SDL_GL_CreateContext(win);
if (context == nullptr) exit(EXIT_FAILURE);
glewInit();
int attrib_vPosition = 0;
const GLchar *vertexShaderSource = { "#version 430 core\n"
"layout (location=0) in vec4 vPosition;"
"uniform mat4 MVPMatrix;"
"void main() {"
" gl_Position = MVPMatrix * vPosition;"
"}"};
GLuint vertexShader = buildShader(&vertexShaderSource, 1, GL_VERTEX_SHADER);
checkGL("compiling vertex shader");
const GLchar *fragShaderSource = { "#version 430 core\n"
"out vec4 fColor;"
"void main() {"
" fColor = vec4(0.0, 0.0, 1.0, 1.0);"
"}"
};
GLuint fragmentShader = buildShader(&fragShaderSource, 1, GL_FRAGMENT_SHADER);
checkGL("compiling fragment shader");
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
checkGLShaderStatus(shaderProgram, GL_LINK_STATUS, false);
checkGL("Linking shader");
glUseProgram(shaderProgram);
//glDeleteShader(fragmentShader);
//glDeleteShader(vertexShader);
checkGL("Running shader");
GLint MVPlocation = glGetUniformLocation(shaderProgram, "MVPMatrix");
checkGL("Getting uniform location");
glm::mat4 mvpMatrix(0.1f);
glUniformMatrix4fv(MVPlocation, 1, GL_FALSE, glm::value_ptr(mvpMatrix));
checkGL("Setting uniform");
GLint testLocation = glGetUniformLocation(shaderProgram, "MVPMatrix[0][0]");
checkGL("Getting uninform test cell location");
GLfloat testfloat;
glGetUniformfv(shaderProgram, testLocation, &testfloat);
checkGL("Reading uniform");
if (testfloat != mvpMatrix[0][0]) {
cout << "Uniform setting did not sink in..";
}
GLuint VAO;
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
checkGL("Creating VAO");
GLfloat vertices[3][3] = { { -0.9f, -0.9f, 0.f }, { 0.85f, -0.9f, 0.f }, { -0.9f, 0.85f, 0.f } };
GLuint buffer;
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
int vertexDataSize = 9;
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, ((void *)(0)));
glEnableVertexAttribArray(0);
checkGL("creating VBO");
glClearColor(0.f, 0.f, 0.f, 1.f);
glClear(GL_COLOR_BUFFER_BIT);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, vertexDataSize);
glFlush();
SDL_GL_SwapWindow(win);
SDL_Event event;
bool quit = false;
while (!quit) {
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT) {
quit = true;
}
}
}
glDeleteProgram(shaderProgram);
glDeleteBuffers(1, &buffer);
glDeleteVertexArrays(1, &VAO);
SDL_GL_DeleteContext(context);
SDL_DestroyRenderer(ren);
SDL_DestroyWindow(win);
IMG_Quit();
SDL_Quit();
return 0;
}
答案 0 :(得分：1)
你不应该使用glGetUniformfv(... glGetUniformLocation(... "MVPMatrix[0][0]"))。文档说
glGetUniformLocation返回一个整数，表示程序对象中特定统一变量的位置。 name必须是不包含空格的空终止字符串。 名称必须是程序 中的活动统一变量名称，它不是结构，结构数组或向量或矩阵的子组件。
和
glGetUniform在 params 中返回指定统一变量的值。 location 指定的统一变量的类型决定了返回的值的数量。如果统一变量在着色器中定义为boolean，int或float，则将返回单个值。如果将其定义为vec2，ivec2或bvec2，则将返回两个值。如果将其定义为vec3，ivec3或bvec3，则将返回三个值，依此类推。要查询存储在声明为数组的统一变量中的值，请为数组的每个元素调用glGetUniform。要查询存储在声明为结构的统一变量中的值，请为结构中的每个字段调用glGetUniform。 声明为矩阵的统一变量的值将按列主要顺序返回。
您的统一变量uniform mat4 MVPMatrix;被声明为a matrix type，而不是an array，您将立即检索整个4x4矩阵（就像您在单个操作中设置它一样）。尝试
GLfloat testfloat[16];
glGetUniformfv(shaderProgram, MVPLocation, testfloat);
另一个问题是：
GLfloat vertices[3][3] = { { -0.9f, -0.9f, 0.f }, { 0.85f, -0.9f, 0.f }, { -0.9f, 0.85f, 0.f } };
int vertexDataSize = 9;
glDrawArrays(GL_TRIANGLES, 0, vertexDataSize);
你没有9个顶点，只有3个顶点。