在上一节的案例中，我们使用了四个Buffer Object，立方体的VertexBuffer，立方体的索引Buffer，四面体的VertexBuffer，四面体的索引Buffer。
我们这节测验考试把两个图形的Vertex Buffer结合，两个图形的索引Buffer结合，形成两个Buffer,让措施越发简化。
先看最终代码： MyGlWindow.cpp:
1 #include <gl\glew.h> 2 #include "MyGlWindow.h" 3 #include <iostream> 4 #include <fstream> 5 #include <glm\gtc\matrix_transform.hpp> 6 #include <glm\gtx\transform.hpp> 7 #include <ShapeGenerator.h> 8 #include <Qt3DInput\qmouseevent.h> 9 #include <Qt3DInput\qkeyevent.h> 10 11 12 GLuint programID; 13 14 15 GLuint VertexBufferID; 16 GLuint IndexBufferID; 17 18 GLuint cubeVertexArrayObjectID; 19 //立方体的索引数组长度 20 GLuint cubeNumIndices; 21 22 GLuint tetraVertexArrayObjectID; 23 //四面体的索引数组长度 24 GLuint tetraNumIndices; 25 26 GLuint tetraIndexByteOffset; 27 28 GLuint fullTransformUniformLocation; 29 30 31 void MyGlWindow::sendDataToOpenGL() 32 { 33 //创建Cube 34 ShapeData cube = ShapeGenerator::makeCube(); 35 //创建四面体 36 ShapeData tetra = ShapeGenerator::makeTetrahedron(); 37 38 //创建和设置VertexBuffer 39 glGenBuffers(1, &VertexBufferID); 40 glBindBuffer(GL_ARRAY_BUFFER, VertexBufferID); 41 glBufferData(GL_ARRAY_BUFFER, cube.vertexBufferSize() + tetra.vertexBufferSize(),0, GL_STATIC_DRAW); 42 glBufferSubData(GL_ARRAY_BUFFER, 0, cube.vertexBufferSize(), cube.vertices); 43 glBufferSubData(GL_ARRAY_BUFFER, cube.vertexBufferSize(), tetra.vertexBufferSize(), tetra.vertices); 44 45 //创建和设置IndexBuffer 46 glGenBuffers(1, &IndexBufferID); 47 glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferID); 48 glBufferData(GL_ELEMENT_ARRAY_BUFFER, cube.indexBufferSize() + tetra.indexBufferSize() , 0, GL_STATIC_DRAW); 49 glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, cube.indexBufferSize(), cube.indices); 50 glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, cube.indexBufferSize(), tetra.indexBufferSize(), tetra.indices); 51 52 53 cubeNumIndices = cube.numIndices; 54 tetraNumIndices = tetra.numIndices; 55 56 57 58 //设置绘制Cube的VAO 59 //生成VAO 60 glGenVertexArrays(1, &cubeVertexArrayObjectID); 61 //绑定VAO，后续的一系列状态和设置城市存储在这个VAO里。 62 glBindVertexArray(cubeVertexArrayObjectID); 63 //开启通道1（位置） 64 glEnableVertexAttribArray(0); 65 //开启通道2（颜色） 66 glEnableVertexAttribArray(1); 67 //绑定极点数据ID到绑定点 68 glBindBuffer(GL_ARRAY_BUFFER, VertexBufferID); 69 //设置通道1如何获取数据 70 glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, 0); 71 //设置通道2如何获取数据 72 glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (void*)(sizeof(float) * 3)); 73 //绑定索引数据ID到绑定点 74 glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferID); 75 76 77 //设置绘制四面体的VAO 78 glGenVertexArrays(1, &tetraVertexArrayObjectID); 79 glBindVertexArray(tetraVertexArrayObjectID); 80 //开启通道1（位置） 81 glEnableVertexAttribArray(0); 82 //开启通道2（颜色） 83 glEnableVertexAttribArray(1); 84 //绑定极点数据ID到绑定点 85 glBindBuffer(GL_ARRAY_BUFFER, VertexBufferID); 86 //设置通道1如何获取数据 87 glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (void*)(cube.vertexBufferSize())); 88 //设置通道2如何获取数据 89 glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(GLfloat) * 6, (void*)(cube.vertexBufferSize() +sizeof(float) * 3)); 90 //绑定索引数据ID到绑定点 91 glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferID); 92 93 tetraIndexByteOffset = cube.indexBufferSize(); 94 95 cube.cleanUp(); 96 tetra.cleanUp(); 97 } 98 99 void MyGlWindow::installShaders() 100 { 101 //... 102 } 103 104 void MyGlWindow::initializeGL() 105 { 106 glewInit(); 107 glEnable(GL_DEPTH_TEST); 108 sendDataToOpenGL(); 109 installShaders(); 110 } 111 112 void MyGlWindow::paintGL() 113 { 114 glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); 115 glViewport(0, 0, width(), height()); 116 117 //绑定cube的VAO，下面绘制的都是立方体-------------------------------------- 118 glBindVertexArray(cubeVertexArrayObjectID); 119 120 glm::mat4 fullTransformMatrix; 121 glm::mat4 viewToProjectionMatrix = glm::perspective(30.0f, ((float)width()) / height(), 0.1f, 10.0f); 122 glm::mat4 worldToViewMatrix = camera.getWorldToViewMatrix(); 123 glm::mat4 worldToProjectionMatrix = viewToProjectionMatrix * worldToViewMatrix; 124 125 //绘制Cube1 126 glm::mat4 cube1ModelToWorldMatrix = 127 glm::translate(glm::vec3(-1.0f, 0.0f, -3.0f))* 128 glm::rotate(36.0f, glm::vec3(1.0f, 0.0f, 0.0f)); 129 130 fullTransformMatrix = worldToProjectionMatrix * cube1ModelToWorldMatrix; 131 glUniformMatrix4fv(fullTransformUniformLocation, 1, GL_FALSE, &fullTransformMatrix[0][0]); 132 glDrawElements(GL_TRIANGLES, cubeNumIndices, GL_UNSIGNED_SHORT, 0); 133 134 //绘制Cube2 135 glm::mat4 cube2ModelToWorldMatrix = 136 glm::translate(glm::vec3(1.0f, 0.0f, -3.75f))* 137 glm::rotate(36.0f, glm::vec3(0.0f, 1.0f, 0.0f)); 138 fullTransformMatrix = worldToProjectionMatrix * cube2ModelToWorldMatrix; 139 glUniformMatrix4fv(fullTransformUniformLocation, 1, GL_FALSE, &fullTransformMatrix[0][0]); 140 glDrawElements(GL_TRIANGLES, cubeNumIndices, GL_UNSIGNED_SHORT, 0); 141 142 //绑定Tetra的VAO，下面绘制的都是四面体-------------------------------------- 143 glBindVertexArray(tetraVertexArrayObjectID); 144 145 //绘制Tetra1 146 glm::mat4 tetra1ModelToWorldMatrix = 147 glm::translate(glm::vec3(1.0f, -2.0f, -3.75f))* 148 glm::rotate(36.0f, glm::vec3(0.0f, 1.0f, 0.0f)); 149 fullTransformMatrix = worldToProjectionMatrix * tetra1ModelToWorldMatrix; 150 glUniformMatrix4fv(fullTransformUniformLocation, 1, GL_FALSE, &fullTransformMatrix[0][0]); 151 glDrawElements(GL_TRIANGLES, tetraNumIndices, GL_UNSIGNED_SHORT, (void*)tetraIndexByteOffset); 152 153 glm::mat4 tetra2ModelToWorldMatrix = 154 glm::translate(glm::vec3(-3.0f, -2.0f, -3.75f))* 155 glm::rotate(36.0f, glm::vec3(1.0f, 1.0f, 0.0f)); 156 fullTransformMatrix = worldToProjectionMatrix * tetra2ModelToWorldMatrix; 157 glUniformMatrix4fv(fullTransformUniformLocation, 1, GL_FALSE, &fullTransformMatrix[0][0]); 158 glDrawElements(GL_TRIANGLES, tetraNumIndices, GL_UNSIGNED_SHORT, (void*)tetraIndexByteOffset); 159 } 160 161 162 std::string MyGlWindow::ReadShaderCode(const char* fileName) 163 { 164 //... 165 } 166 167 void MyGlWindow::mouseMoveEvent(QMouseEvent * e) 168 { 169 //... 170 } 171 172 void MyGlWindow::keyPressEvent(QKeyEvent * e) 173 { 174 //... 175 }
注意：为了便利起见，我们把原先setupVertexArray函数的内容全部移动到sendDataToOpenGL函数中了。
下面详解窜改的过程：
首先合并了两个极点数组和两个索引数组, cubeVertexBufferID + tetraVertexBufferID -> VertexBufferID， cubeIndexBufferID + tetraIndexBufferID -> IndexBufferID。
在sendDataToOpenGL()函数的一开始，我们先界说好两个图形。