前言
openGL使用GLFW、GLEW庫繪制點,下面這段代碼:繪制藍色背景,中心點是一個黃色的點,由于代碼比較簡單,是以我把頂點着色器和片元着色器寫死到c++程式中。問題就在這!!!由于着色器都寫在字元串中,造成着色器的錯誤很難排查。
#include "glew/glew.h"
#include "glfw/glfw3.h"
#include <iostream>
using namespace std;
static const unsigned int scr_width = 800;
static const unsigned int scr_height = 600;
static const int numVAOs = 1;
GLuint renderingProgram;
GLuint vao[numVAOs];
static void error_callback(int error, const char* description)
{
fprintf_s(stderr, "Error:%s\n", description);
}
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
{
glfwSetWindowShouldClose(window, GLFW_TRUE);
}
}
GLuint createShaderProgram()
{
const char* vShaderSource =
"#version core 430 \n"
"void main(void) \n"
"{ \n"
" gl_Position = vec4(0.f, 0.f, 0.f, 1.f); \n"
"} \n";
const char* fShaderSource =
"#version core 430 \n"
"out vec4 fragColor; \n"
"void main(void) \n"
"{ \n"
" fragColor = vec4(1.0f, 1.0f, 0.0f, 1.0f); \n"
"} \n";
GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vShader, 1, &vShaderSource, nullptr);
glShaderSource(fShader, 1, &fShaderSource, nullptr);
glCompileShader(vShader);
glCompileShader(fShader);
GLuint vfProgram = glCreateProgram();
glAttachShader(vfProgram, vShader);
glAttachShader(vfProgram, fShader);
glLinkProgram(vfProgram);
return vfProgram;
}
void init(GLFWwindow* window)
{
renderingProgram = createShaderProgram();
//緩沖區最後都會被存入頂點數組對象VAO(Vertex Array Object)
glGenVertexArrays(numVAOs, vao);
glBindVertexArray(vao[0]);
}
void display(GLFWwindow* window, double currentTime)
{
glClearColor(0.f, 0.f, 1.f, 1.f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(renderingProgram);
glPointSize(30.0f);
glDrawArrays(GL_POINTS, 0, 1);
}
int main(int argc, char** argv)
{
int glfwState = glfwInit();
if (GLFW_FALSE == glfwState)
{
cout << "GLFW initialize failed. Invoke glfwInit()." << std::endl;
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwSetErrorCallback(error_callback);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
GLFWwindow* window = glfwCreateWindow(scr_width, scr_height, "Draw point", nullptr, nullptr);
if (nullptr == window)
{
cout << "GLFW create window failed! Invoke glfwCreateWindow()." << std::endl;
//釋放GLFW所有資源,直到調用glfwInit才能重新擷取GLFW資源
glfwTerminate();
exit(EXIT_FAILURE);
}
//用于設定指定視窗的鍵回調,在按下、重複或釋放鍵時調用該視窗
glfwSetKeyCallback(window, key_callback);
//調用線程上指定視窗的OpenGL或OpenGL ES上下文成為目前上下文。上下文一次隻能在單個線程上成為目前上下文,并且每個線程一次隻能有一個目前上下文。
glfwMakeContextCurrent(window);
int glewState = glewInit();
if (GLEW_OK != glewState)
{
cout << "GLEW initialize failed! Invoke glfwInit()." << std::endl;
exit(EXIT_FAILURE);
}
//由于這些原因,應用程式通常希望将交換間隔設定為1。可以将其設定為更高的值,但通常不建議這樣做,因為這樣會導緻輸入延遲。
glfwSwapInterval(1);
init(window);
while (!glfwWindowShouldClose(window))
{
display(window, glfwGetTime());
glfwSwapBuffers(window);
glfwPollEvents();
}
//銷毀視窗,以及撤銷視窗事件
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
return 0;
}
程式運作結果:
問題定位
1.首先背景顔色是對的,但中間的點顔色不對,而且程式沒有報錯。可以确定GLFW、GLEW、openGL庫這些都 沒問題。
2.程式着色器貌似沒有問題
問題解決
問題就在着色器程式上:
把 #version core 430
改成:
#version 430 core
或者
#version 430