最简单的 MRTs(Multi Render Targets)的完整代码示例【OpenGL】
【摘要】
MRTs 允许应用程序同时渲染多个颜色缓冲区
话不多言，详细代码和注释如下：
// HelloBlitFramebuffer.cpp : 定义控制台应用程序的入口点。// #include "stdafx.h"#include <iostream>#include <GL/glew.h>#include ...
MRTs 允许应用程序同时渲染多个颜色缓冲区
话不多言，详细代码和注释如下：
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// HelloBlitFramebuffer.cpp : 定义控制台应用程序的入口点。
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//
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#include "stdafx.h"
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#include <iostream>
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#include <GL/glew.h>
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#include <gl/freeglut.h>
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// -----------------------------------
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typedef struct
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{
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// Handle to a program object
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GLuint programObject;
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// Handle to a framebuffer object
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GLuint fbo;
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// Texture handle
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GLuint colorTexId[4];
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// Texture size
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GLsizei textureWidth;
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GLsizei textureHeight;
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} UserData;
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UserData *userData = NULL;
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const GLenum attachments[4] =
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{
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GL_COLOR_ATTACHMENT0,
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GL_COLOR_ATTACHMENT1,
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GL_COLOR_ATTACHMENT2,
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GL_COLOR_ATTACHMENT3
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};
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#define SCREEN_W 640
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#define SCREEN_H 640
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///
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// 初始化 FBO 和 MRTs
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//
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int InitFBO()
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{
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int i;
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GLint defaultFramebuffer = 0;
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glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFramebuffer);
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// 创建 FBO
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glGenFramebuffers(1, &userData->fbo);
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glBindFramebuffer(GL_FRAMEBUFFER, userData->fbo);
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// 创建4个输出纹理，并绑定到 FBO
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userData->textureHeight = userData->textureWidth = 400;
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glGenTextures(4, &userData->colorTexId[0]);
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for (i = 0; i < 4; ++i)
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{
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glBindTexture(GL_TEXTURE_2D, userData->colorTexId[i]);
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glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
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userData->textureWidth, userData->textureHeight,
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0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
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// 设置过滤模式
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
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glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, attachments[i],
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GL_TEXTURE_2D, userData->colorTexId[i], 0);
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}
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// 指定待写入的 color buffers
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glDrawBuffers(4, attachments);
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if (GL_FRAMEBUFFER_COMPLETE != glCheckFramebufferStatus(GL_FRAMEBUFFER))
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{
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return FALSE;
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}
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// 恢复默认的 framebuffer
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glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
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return TRUE;
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}
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// 初始化 Shader Program，返回 Program ID
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GLuint InitShaders(const char *vs, const char *fs)
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{
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GLint vertCompiled, fragCompiled, linked;
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// Shaders
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GLint v = glCreateShader(GL_VERTEX_SHADER);
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GLint f = glCreateShader(GL_FRAGMENT_SHADER);
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glShaderSource(v, 1, &vs, NULL);
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glShaderSource(f, 1, &fs, NULL);
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glCompileShader(v);
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glGetShaderiv(v, GL_COMPILE_STATUS, &vertCompiled); // Debug
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if (vertCompiled != GL_TRUE)
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{
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printf("Vertex Shader compied error! \n");
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}
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glCompileShader(f);
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glGetShaderiv(f, GL_COMPILE_STATUS, &fragCompiled);
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if (fragCompiled != GL_TRUE)
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{
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printf("Fragment Shader compied error! \n");
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}
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//Program:
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GLuint p = glCreateProgram();
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glAttachShader(p, v);
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glAttachShader(p, f);
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glLinkProgram(p);
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glGetProgramiv(p, GL_LINK_STATUS, &linked); // Debug
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if (linked != GL_TRUE)
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{
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printf("Program linked error! \n");
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}
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return p;
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}
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///
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// 初始化 shader 和 program
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//
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int Init()
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{
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const char vShaderStr[] =
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//"#version 300 es \n"
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"#version 330 \n"
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"layout(location = 0) in vec4 a_position; \n"
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"void main() \n"
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"{ \n"
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" gl_Position = a_position; \n"
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"} \n";
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const char fShaderStr[] =
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//"#version 300 es \n"
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//"precision mediump float; \n"
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"#version 330 \n"
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"layout(location = 0) out vec4 fragData0; \n"
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"layout(location = 1) out vec4 fragData1; \n"
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"layout(location = 2) out vec4 fragData2; \n"
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"layout(location = 3) out vec4 fragData3; \n"
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"void main() \n"
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"{ \n"
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" // first buffer will contain red color \n"
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" fragData0 = vec4 ( 1, 0, 0, 1 ); \n"
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" \n"
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" // second buffer will contain green color \n"
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" fragData1 = vec4 ( 0, 1, 0, 1 ); \n"
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" \n"
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" // third buffer will contain blue color \n"
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" fragData2 = vec4 ( 0, 0, 1, 1 ); \n"
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" \n"
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" // fourth buffer will contain gray color \n"
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" fragData3 = vec4 ( 0.5, 0.5, 0.5, 1 ); \n"
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"} \n";
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userData->programObject = InitShaders(vShaderStr, fShaderStr);
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InitFBO();
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glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
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return TRUE;
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}
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///
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// 绘制一个 Quad
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//
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void DrawGeometry()
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{
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GLfloat vVertices[] = { -1.0f, 1.0f, 0.0f,
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-1.0f, -1.0f, 0.0f,
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1.0f, -1.0f, 0.0f,
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1.0f, 1.0f, 0.0f,
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};
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GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
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glViewport(0, 0, SCREEN_W, SCREEN_H);
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glClear(GL_COLOR_BUFFER_BIT);
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glUseProgram(userData->programObject);
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glVertexAttribPointer(0, 3, GL_FLOAT,
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GL_FALSE, 3 * sizeof(GLfloat), vVertices);
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glEnableVertexAttribArray(0);
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glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);
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}
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///
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// ☆ 拷贝 MRTs 的输出到屏幕 ☆
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//
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void BlitTextures()
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{
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// 绑定 FBO，用于读取
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glBindFramebuffer(GL_READ_FRAMEBUFFER, userData->fbo);
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// 选择一块 color buffer 作为源，拷贝输出到屏幕指定位置
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glReadBuffer(GL_COLOR_ATTACHMENT0);
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glBlitFramebuffer(0, 0, userData->textureWidth, userData->textureHeight,
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0, 0,
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SCREEN_W / 2, SCREEN_H / 2, // 左下角坐标
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GL_COLOR_BUFFER_BIT, GL_LINEAR);
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glReadBuffer(GL_COLOR_ATTACHMENT1);
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glBlitFramebuffer(0, 0, userData->textureWidth, userData->textureHeight,
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SCREEN_W / 2, 0,
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SCREEN_W, SCREEN_H / 2, // 右下角坐标
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GL_COLOR_BUFFER_BIT, GL_LINEAR);
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glReadBuffer(GL_COLOR_ATTACHMENT2);
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glBlitFramebuffer(0, 0, userData->textureWidth, userData->textureHeight,
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0, SCREEN_H / 2,
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SCREEN_W / 2, SCREEN_H, // 左上角坐标
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GL_COLOR_BUFFER_BIT, GL_LINEAR);
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glReadBuffer(GL_COLOR_ATTACHMENT3);
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glBlitFramebuffer(0, 0, userData->textureWidth, userData->textureHeight,
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SCREEN_W / 2, SCREEN_H / 2, // 右上角坐标
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SCREEN_W, SCREEN_H,
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GL_COLOR_BUFFER_BIT, GL_LINEAR);
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}
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///
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// 清理善后
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//
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void ShutDown()
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{
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glDeleteTextures(4, userData->colorTexId);
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glDeleteFramebuffers(1, &userData->fbo);
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glDeleteProgram(userData->programObject);
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}
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// -----------------------------------
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// 键盘响应事件
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static void ProcessNormalKeys(unsigned char key, int x, int y)
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{
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// Esc
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if (key == 27)
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{
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ShutDown();
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exit(0);
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}
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}
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static void Display()
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{
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GLint defaultFramebuffer = 0;
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glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFramebuffer);
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// 使用 MRTs 输出4种颜色至4块缓冲区
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glBindFramebuffer(GL_FRAMEBUFFER, userData->fbo);
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glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
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glDrawBuffers(4, attachments);
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DrawGeometry();
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// 恢复默认 framebuffer
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// 从之前的4块缓冲区中拷贝像素到屏幕指定位置
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glBindFramebuffer(GL_DRAW_FRAMEBUFFER, defaultFramebuffer);
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BlitTextures();
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glutSwapBuffers();
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}
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int main(int argc, char* argv[])
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{
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glutInit(&argc, argv);
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glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA /*| GLUT_STENCIL | GLUT_DEPTH*/);
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glutInitWindowPosition(100, 100);
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glutInitWindowSize(SCREEN_W, SCREEN_H);
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glutCreateWindow("Hello BlitFramebuffer !");
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GLenum err = glewInit();
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if (err != GLEW_OK)
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{
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fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
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exit(-2);
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}
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userData = new UserData;
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if (!Init())
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{
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return GL_FALSE;
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}
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glutDisplayFunc(Display);
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glutIdleFunc(&Display);
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glutKeyboardFunc(ProcessNormalKeys);
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glutMainLoop();
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return 0;
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}
结果：
文章来源: panda1234lee.blog.csdn.net，作者：panda1234lee，版权归原作者所有，如需转载，请联系作者。
原文链接：panda1234lee.blog.csdn.net/article/details/54287825
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