我刚刚了解了透视投影，并且发现在 openGl 中应用它有点令人困惑。
考虑一个简单的 Square 。
在使用透视投影之前，我可以在 [-1,1] 空间中定义其顶点的坐标，输入为 {0.0f,0.0f,0.0f,1.0f,1.0f,1.0f,1.0f,0.0 f} ，正方形将占据窗口的第一象限。
考虑我的代码中的以下部分：
设置矩阵：
glm::mat4 mvp(1.0);
mvp*=glm::perspective(45.0f,1.0f,0.01f,100.0f);
制服：
loc = glGetUniformLocation(program.getHandle(),"mvp");
glUniformMatrix4fv(loc,1,GL_FALSE,glm::value_ptr(mvp));
顶点着色器：
#version 330
in vec2 pos;
uniform mat4 mvp;
void main()
{
gl_Position = mvp*vec4(pos,0.0f,1.0f);
}
但是，结果是一个空白屏幕。
我需要在这里应用哪些额外的转换？
另外，顶点数据应该在哪个坐标中？
这是完整的代码：
#include "program.h"
#include <GL/glew.h>
#include <SFML/Window.hpp>
#include <stdexcept>
#include <iostream>
#include <glm/glm.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/core/type.hpp>
void GlewInit()
{
GLenum err = glewInit();
if (GLEW_OK != err)
{
std::cerr<<"Error: "<<glewGetErrorString(err)<<std::endl;
throw(std::runtime_error("GLEW_INIT Failure."));
}
}
int main()
{
sf::Window win(sf::VideoMode(400,400),"Manasij");
GlewInit();
float vertexdata[]={0.0f,0.0f,0.0f,1.0f,1.0f,1.0f,1.0f,0.0f};
GLubyte indexdata[]={0,1,2,3};
float colordata[]={0.3f,0.0f,0.5f,1.0f};
mm::Program program
(
{
mm::Shader(GL_VERTEX_SHADER,"vshader.vert"),
mm::Shader(GL_FRAGMENT_SHADER,"fshader.frag")
}
);
glm::mat4 mvp(1.0);
mvp*=glm::perspective(45.0f,1.0f,0.01f,100.0f);
GLuint vao,vbo,ibo;
glGenVertexArrays(1,&vao);
glBindVertexArray(vao);
glGenBuffers(1,&vbo);
glBindBuffer(GL_ARRAY_BUFFER,vbo);
glBufferData(GL_ARRAY_BUFFER,8*sizeof(GLfloat),vertexdata,GL_STATIC_DRAW);
glGenBuffers(1,&ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,4*sizeof(GLubyte),indexdata,GL_STATIC_DRAW);
glVertexAttribPointer(0,2,GL_FLOAT,GL_FALSE,0,0);
glEnableVertexAttribArray(0);
glBindAttribLocation(program.getHandle(),0,"pos");
glUseProgram(program.getHandle());
auto loc = glGetUniformLocation(program.getHandle(),"col");
glUniform4fv(loc,1,colordata);
loc = glGetUniformLocation(program.getHandle(),"mvp");
glUniformMatrix4fv(loc,1,GL_FALSE,glm::value_ptr(mvp));
glUseProgram(0);
glClearColor(1.0f,1.0f,1.0f,1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
while(win.isOpen())
{
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program.getHandle());
// glDrawArrays(GL_QUADS,0,4);
glDrawElements(GL_QUADS,4,GL_UNSIGNED_BYTE,nullptr);
glUseProgram(0);
win.display();
sf::Event eve;
while(win.pollEvent(eve))
if(eve.type==sf::Event::Closed)
win.close();
}
return 0;
}