opengl 学习 之 11 lesson
简介
2D纹理。简单来说就是用一个四边形的小框框，UV映射图片。
这里用了多个shader，一个是关于模型的，一个是关于图片的。
link
http://www.opengl-tutorial.org/uncategorized/2017/06/07/website-update/
步骤
bind the buffers, fifill them, select the shader program, bind the texture, enable/bind/confifigure the vertex attributes, enable the blending, and call glDrawArrays.
code
// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <vector>
// Include GLEW
#include <GL/glew.h>
// Include GLFW
#include <GLFW/glfw3.h>
GLFWwindow* window;
// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;
#include <common/shader.hpp>
#include <common/texture.hpp>
#include <common/controls.hpp>
#include <common/objloader.hpp>
#include <common/vboindexer.hpp>
#include <common/text2D.hpp>
int main( void )
{
// Initialise GLFW
if( !glfwInit() )
{
fprintf( stderr, "Failed to initialize GLFW
" );
getchar();
return -1;
}
glfwWindowHint(GLFW_SAMPLES, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// Open a window and create its OpenGL context
window = glfwCreateWindow( 1024, 768, "Tutorial 11 - 2D Fonts", NULL, NULL);
if( window == NULL ){
fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.
" );
getchar();
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
// Initialize GLEW
glewExperimental = true; // Needed for core profile
if (glewInit() != GLEW_OK) {
fprintf(stderr, "Failed to initialize GLEW
");
getchar();
glfwTerminate();
return -1;
}
// Ensure we can capture the escape key being pressed below
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
// Hide the mouse and enable unlimited mouvement
glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
// Set the mouse at the center of the screen
glfwPollEvents();
glfwSetCursorPos(window, 1024/2, 768/2);
// Dark blue background
glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
// Enable depth test
glEnable(GL_DEPTH_TEST);
// Accept fragment if it closer to the camera than the former one
glDepthFunc(GL_LESS);
// Cull triangles which normal is not towards the camera
glEnable(GL_CULL_FACE);
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
// Create and compile our GLSL program from the shaders
GLuint programID = LoadShaders( "StandardShading.vertexshader", "StandardShading.fragmentshader" );
// Get a handle for our "MVP" uniform
GLuint MatrixID = glGetUniformLocation(programID, "MVP");
GLuint ViewMatrixID = glGetUniformLocation(programID, "V");
GLuint ModelMatrixID = glGetUniformLocation(programID, "M");
// Load the texture
GLuint Texture = loadDDS("uvmap.DDS");
// Get a handle for our "myTextureSampler" uniform
GLuint TextureID = glGetUniformLocation(programID, "myTextureSampler");
// Read our .obj file
std::vector<glm::vec3> vertices;
std::vector<glm::vec2> uvs;
std::vector<glm::vec3> normals;
bool res = loadOBJ("suzanne.obj", vertices, uvs, normals);
std::vector<unsigned short> indices;
std::vector<glm::vec3> indexed_vertices;
std::vector<glm::vec2> indexed_uvs;
std::vector<glm::vec3> indexed_normals;
indexVBO(vertices, uvs, normals, indices, indexed_vertices, indexed_uvs, indexed_normals);
// Load it into a VBO
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_vertices.size() * sizeof(glm::vec3), &indexed_vertices[0], GL_STATIC_DRAW);
GLuint uvbuffer;
glGenBuffers(1, &uvbuffer);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_uvs.size() * sizeof(glm::vec2), &indexed_uvs[0], GL_STATIC_DRAW);
GLuint normalbuffer;
glGenBuffers(1, &normalbuffer);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_normals.size() * sizeof(glm::vec3), &indexed_normals[0], GL_STATIC_DRAW);
// Generate a buffer for the indices as well
GLuint elementbuffer;
glGenBuffers(1, &elementbuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(unsigned short), &indices[0], GL_STATIC_DRAW);
// Get a handle for our "LightPosition" uniform
glUseProgram(programID);
GLuint LightID = glGetUniformLocation(programID, "LightPosition_worldspace");
// Initialize our little text library with the Holstein font
initText2D( "Holstein.DDS" );
// For speed computation
double lastTime = glfwGetTime();
int nbFrames = 0;
do{
// Measure speed
double currentTime = glfwGetTime();
nbFrames++;
if ( currentTime - lastTime >= 1.0 ){ // If last prinf() was more than 1sec ago
// printf and reset
printf("%f ms/frame
", 1000.0/double(nbFrames));
nbFrames = 0;
lastTime += 1.0;
}
// Clear the screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Use our shader
glUseProgram(programID);
// Compute the MVP matrix from keyboard and mouse input
computeMatricesFromInputs();
glm::mat4 ProjectionMatrix = getProjectionMatrix();
glm::mat4 ViewMatrix = getViewMatrix();
glm::mat4 ModelMatrix = glm::mat4(1.0);
glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &ModelMatrix[0][0]);
glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);
glm::vec3 lightPos = glm::vec3(4,4,4);
glUniform3f(LightID, lightPos.x, lightPos.y, lightPos.z);
// Bind our texture in Texture Unit 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, Texture);
// Set our "myTextureSampler" sampler to use Texture Unit 0
glUniform1i(TextureID, 0);
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(
0, // attribute
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2nd attribute buffer : UVs
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glVertexAttribPointer(
1, // attribute
2, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 3rd attribute buffer : normals
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glVertexAttribPointer(
2, // attribute
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// Index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
// Draw the triangles !
glDrawElements(
GL_TRIANGLES, // mode
indices.size(), // count
GL_UNSIGNED_SHORT, // type
(void*)0 // element array buffer offset
);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
char text[256];
sprintf(text,"%.2f sec", glfwGetTime() );
printText2D(text, 10, 500, 60);
// Swap buffers
glfwSwapBuffers(window);
glfwPollEvents();
} // Check if the ESC key was pressed or the window was closed
while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
glfwWindowShouldClose(window) == 0 );
// Cleanup VBO, shader and texture
glDeleteBuffers(1, &vertexbuffer);
glDeleteBuffers(1, &uvbuffer);
glDeleteBuffers(1, &normalbuffer);
glDeleteBuffers(1, &elementbuffer);
glDeleteProgram(programID);
glDeleteTextures(1, &Texture);
glDeleteVertexArrays(1, &VertexArrayID);
// Delete the text's VBO, the shader and the texture
cleanupText2D();
// Close OpenGL window and terminate GLFW
glfwTerminate();
return 0;
}
#ifndef TEXT2D_HPP
#define TEXT2D_HPP
void initText2D(const char * texturePath);
void printText2D(const char * text, int x, int y, int size);
void cleanupText2D();
#endif
#include <vector>
#include <cstring>
#include <GL/glew.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;
#include "shader.hpp"
#include "texture.hpp"
#include "text2D.hpp"
unsigned int Text2DTextureID;
unsigned int Text2DVertexBufferID;
unsigned int Text2DUVBufferID;
unsigned int Text2DShaderID;
unsigned int Text2DUniformID;
void initText2D(const char * texturePath){
// Initialize texture
Text2DTextureID = loadDDS(texturePath);
// Initialize VBO
glGenBuffers(1, &Text2DVertexBufferID);
glGenBuffers(1, &Text2DUVBufferID);
// Initialize Shader
Text2DShaderID = LoadShaders( "TextVertexShader.vertexshader", "TextVertexShader.fragmentshader" );
// Initialize uniforms' IDs
Text2DUniformID = glGetUniformLocation( Text2DShaderID, "myTextureSampler" );
}
void printText2D(const char * text, int x, int y, int size){
unsigned int length = strlen(text);
// Fill buffers
std::vector<glm::vec2> vertices;
std::vector<glm::vec2> UVs;
for ( unsigned int i=0 ; i<length ; i++ ){
glm::vec2 vertex_up_left = glm::vec2( x+i*size , y+size );
glm::vec2 vertex_up_right = glm::vec2( x+i*size+size, y+size );
glm::vec2 vertex_down_right = glm::vec2( x+i*size+size, y );
glm::vec2 vertex_down_left = glm::vec2( x+i*size , y );
vertices.push_back(vertex_up_left );
vertices.push_back(vertex_down_left );
vertices.push_back(vertex_up_right );
vertices.push_back(vertex_down_right);
vertices.push_back(vertex_up_right);
vertices.push_back(vertex_down_left);
char character = text[i];
float uv_x = (character%16)/16.0f;
float uv_y = (character/16)/16.0f;
glm::vec2 uv_up_left = glm::vec2( uv_x , uv_y );
glm::vec2 uv_up_right = glm::vec2( uv_x+1.0f/16.0f, uv_y );
glm::vec2 uv_down_right = glm::vec2( uv_x+1.0f/16.0f, (uv_y + 1.0f/16.0f) );
glm::vec2 uv_down_left = glm::vec2( uv_x , (uv_y + 1.0f/16.0f) );
UVs.push_back(uv_up_left );
UVs.push_back(uv_down_left );
UVs.push_back(uv_up_right );
UVs.push_back(uv_down_right);
UVs.push_back(uv_up_right);
UVs.push_back(uv_down_left);
}
glBindBuffer(GL_ARRAY_BUFFER, Text2DVertexBufferID);
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec2), &vertices[0], GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, Text2DUVBufferID);
glBufferData(GL_ARRAY_BUFFER, UVs.size() * sizeof(glm::vec2), &UVs[0], GL_STATIC_DRAW);
// Bind shader
glUseProgram(Text2DShaderID);
// Bind texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, Text2DTextureID);
// Set our "myTextureSampler" sampler to use Texture Unit 0
glUniform1i(Text2DUniformID, 0);
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, Text2DVertexBufferID);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (void*)0 );
// 2nd attribute buffer : UVs
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, Text2DUVBufferID);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0 );
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// Draw call
glDrawArrays(GL_TRIANGLES, 0, vertices.size() );
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
}
void cleanupText2D(){
// Delete buffers
glDeleteBuffers(1, &Text2DVertexBufferID);
glDeleteBuffers(1, &Text2DUVBufferID);
// Delete texture
glDeleteTextures(1, &Text2DTextureID);
// Delete shader
glDeleteProgram(Text2DShaderID);
}
#version 330 core
// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec2 vertexPosition_screenspace;
layout(location = 1) in vec2 vertexUV;
// Output data ; will be interpolated for each fragment.
out vec2 UV;
void main(){
// Output position of the vertex, in clip space
// map [0..800][0..600] to [-1..1][-1..1]
vec2 vertexPosition_homoneneousspace = vertexPosition_screenspace - vec2(400,300); // [0..800][0..600] -> [-400..400][-300..300]
vertexPosition_homoneneousspace /= vec2(400,300);
gl_Position = vec4(vertexPosition_homoneneousspace,0,1);
// UV of the vertex. No special space for this one.
UV = vertexUV;
}
#version 330 core
// Interpolated values from the vertex shaders
in vec2 UV;
// Ouput data
out vec4 color;
// Values that stay constant for the whole mesh.
uniform sampler2D myTextureSampler;
void main(){
color = texture( myTextureSampler, UV );
}