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50
51#include "geometryengine.h"
52
53#include <QVector2D>
54#include <QVector3D>
55
56struct VertexData
57{
58 QVector3D position;
59 QVector2D texCoord;
60};
61
62//! [0]
63GeometryEngine::GeometryEngine()
64 : indexBuf(QOpenGLBuffer::IndexBuffer)
65{
66 initializeOpenGLFunctions();
67
68 // Generate 2 VBOs
69 arrayBuf.create();
70 indexBuf.create();
71
72 // Initializes cube geometry and transfers it to VBOs
73 initCubeGeometry();
74}
75
76GeometryEngine::~GeometryEngine()
77{
78 arrayBuf.destroy();
79 indexBuf.destroy();
80}
81//! [0]
82
83void GeometryEngine::initCubeGeometry()
84{
85 // For cube we would need only 8 vertices but we have to
86 // duplicate vertex for each face because texture coordinate
87 // is different.
88 VertexData vertices[] = {
89 // Vertex data for face 0
90 {QVector3D(-1.0f, -1.0f, 1.0f), QVector2D(0.0f, 0.0f)}, // v0
91 {QVector3D( 1.0f, -1.0f, 1.0f), QVector2D(0.33f, 0.0f)}, // v1
92 {QVector3D(-1.0f, 1.0f, 1.0f), QVector2D(0.0f, 0.5f)}, // v2
93 {QVector3D( 1.0f, 1.0f, 1.0f), QVector2D(0.33f, 0.5f)}, // v3
94
95 // Vertex data for face 1
96 {QVector3D( 1.0f, -1.0f, 1.0f), QVector2D( 0.0f, 0.5f)}, // v4
97 {QVector3D( 1.0f, -1.0f, -1.0f), QVector2D(0.33f, 0.5f)}, // v5
98 {QVector3D( 1.0f, 1.0f, 1.0f), QVector2D(0.0f, 1.0f)}, // v6
99 {QVector3D( 1.0f, 1.0f, -1.0f), QVector2D(0.33f, 1.0f)}, // v7
100
101 // Vertex data for face 2
102 {QVector3D( 1.0f, -1.0f, -1.0f), QVector2D(0.66f, 0.5f)}, // v8
103 {QVector3D(-1.0f, -1.0f, -1.0f), QVector2D(1.0f, 0.5f)}, // v9
104 {QVector3D( 1.0f, 1.0f, -1.0f), QVector2D(0.66f, 1.0f)}, // v10
105 {QVector3D(-1.0f, 1.0f, -1.0f), QVector2D(1.0f, 1.0f)}, // v11
106
107 // Vertex data for face 3
108 {QVector3D(-1.0f, -1.0f, -1.0f), QVector2D(0.66f, 0.0f)}, // v12
109 {QVector3D(-1.0f, -1.0f, 1.0f), QVector2D(1.0f, 0.0f)}, // v13
110 {QVector3D(-1.0f, 1.0f, -1.0f), QVector2D(0.66f, 0.5f)}, // v14
111 {QVector3D(-1.0f, 1.0f, 1.0f), QVector2D(1.0f, 0.5f)}, // v15
112
113 // Vertex data for face 4
114 {QVector3D(-1.0f, -1.0f, -1.0f), QVector2D(0.33f, 0.0f)}, // v16
115 {QVector3D( 1.0f, -1.0f, -1.0f), QVector2D(0.66f, 0.0f)}, // v17
116 {QVector3D(-1.0f, -1.0f, 1.0f), QVector2D(0.33f, 0.5f)}, // v18
117 {QVector3D( 1.0f, -1.0f, 1.0f), QVector2D(0.66f, 0.5f)}, // v19
118
119 // Vertex data for face 5
120 {QVector3D(-1.0f, 1.0f, 1.0f), QVector2D(0.33f, 0.5f)}, // v20
121 {QVector3D( 1.0f, 1.0f, 1.0f), QVector2D(0.66f, 0.5f)}, // v21
122 {QVector3D(-1.0f, 1.0f, -1.0f), QVector2D(0.33f, 1.0f)}, // v22
123 {QVector3D( 1.0f, 1.0f, -1.0f), QVector2D(0.66f, 1.0f)} // v23
124 };
125
126 // Indices for drawing cube faces using triangle strips.
127 // Triangle strips can be connected by duplicating indices
128 // between the strips. If connecting strips have opposite
129 // vertex order then last index of the first strip and first
130 // index of the second strip needs to be duplicated. If
131 // connecting strips have same vertex order then only last
132 // index of the first strip needs to be duplicated.
133 GLushort indices[] = {
134 0, 1, 2, 3, 3, // Face 0 - triangle strip ( v0, v1, v2, v3)
135 4, 4, 5, 6, 7, 7, // Face 1 - triangle strip ( v4, v5, v6, v7)
136 8, 8, 9, 10, 11, 11, // Face 2 - triangle strip ( v8, v9, v10, v11)
137 12, 12, 13, 14, 15, 15, // Face 3 - triangle strip (v12, v13, v14, v15)
138 16, 16, 17, 18, 19, 19, // Face 4 - triangle strip (v16, v17, v18, v19)
139 20, 20, 21, 22, 23 // Face 5 - triangle strip (v20, v21, v22, v23)
140 };
141
142//! [1]
143 // Transfer vertex data to VBO 0
144 arrayBuf.bind();
145 arrayBuf.allocate(vertices, 24 * sizeof(VertexData));
146
147 // Transfer index data to VBO 1
148 indexBuf.bind();
149 indexBuf.allocate(indices, 34 * sizeof(GLushort));
150//! [1]
151}
152
153//! [2]
154void GeometryEngine::drawCubeGeometry(QOpenGLShaderProgram *program)
155{
156 // Tell OpenGL which VBOs to use
157 arrayBuf.bind();
158 indexBuf.bind();
159
160 // Offset for position
161 quintptr offset = 0;
162
163 // Tell OpenGL programmable pipeline how to locate vertex position data
164 int vertexLocation = program->attributeLocation("a_position");
165 program->enableAttributeArray(vertexLocation);
166 program->setAttributeBuffer(vertexLocation, GL_FLOAT, offset, 3, sizeof(VertexData));
167
168 // Offset for texture coordinate
169 offset += sizeof(QVector3D);
170
171 // Tell OpenGL programmable pipeline how to locate vertex texture coordinate data
172 int texcoordLocation = program->attributeLocation("a_texcoord");
173 program->enableAttributeArray(texcoordLocation);
174 program->setAttributeBuffer(texcoordLocation, GL_FLOAT, offset, 2, sizeof(VertexData));
175
176 // Draw cube geometry using indices from VBO 1
177 glDrawElements(GL_TRIANGLE_STRIP, 34, GL_UNSIGNED_SHORT, nullptr);
178}
179//! [2]
180