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#include "geometryengine.h"#include <QVector2D>#include <QVector3D>struct VertexData
{
QVector3D position;
QVector2D texCoord;
};
GeometryEngine::GeometryEngine()
: indexBuf(QOpenGLBuffer::IndexBuffer)
{
initializeOpenGLFunctions();
// Generate 2 VBOs
arrayBuf.create();
indexBuf.create();
// Initializes cube geometry and transfers it to VBOs
initCubeGeometry();
}
GeometryEngine::~GeometryEngine()
{
arrayBuf.destroy();
indexBuf.destroy();
}
void GeometryEngine::initCubeGeometry()
{
// For cube we would need only 8 vertices but we have to// duplicate vertex for each face because texture coordinate// is different.
VertexData vertices[]= {
// Vertex data for face 0
{QVector3D(-1.0f,-1.0f,1.0f), QVector2D(0.0f,0.0f)},// v0
{QVector3D( 1.0f,-1.0f,1.0f), QVector2D(0.33f,0.0f)},// v1
{QVector3D(-1.0f,1.0f,1.0f), QVector2D(0.0f,0.5f)},// v2
{QVector3D( 1.0f,1.0f,1.0f), QVector2D(0.33f,0.5f)},// v3// Vertex data for face 1
{QVector3D( 1.0f,-1.0f,1.0f), QVector2D( 0.0f,0.5f)},// v4
{QVector3D( 1.0f,-1.0f,-1.0f), QVector2D(0.33f,0.5f)},// v5
{QVector3D( 1.0f,1.0f,1.0f), QVector2D(0.0f,1.0f)},// v6
{QVector3D( 1.0f,1.0f,-1.0f), QVector2D(0.33f,1.0f)},// v7// Vertex data for face 2
{QVector3D( 1.0f,-1.0f,-1.0f), QVector2D(0.66f,0.5f)},// v8
{QVector3D(-1.0f,-1.0f,-1.0f), QVector2D(1.0f,0.5f)},// v9
{QVector3D( 1.0f,1.0f,-1.0f), QVector2D(0.66f,1.0f)},// v10
{QVector3D(-1.0f,1.0f,-1.0f), QVector2D(1.0f,1.0f)},// v11// Vertex data for face 3
{QVector3D(-1.0f,-1.0f,-1.0f), QVector2D(0.66f,0.0f)},// v12
{QVector3D(-1.0f,-1.0f,1.0f), QVector2D(1.0f,0.0f)},// v13
{QVector3D(-1.0f,1.0f,-1.0f), QVector2D(0.66f,0.5f)},// v14
{QVector3D(-1.0f,1.0f,1.0f), QVector2D(1.0f,0.5f)},// v15// Vertex data for face 4
{QVector3D(-1.0f,-1.0f,-1.0f), QVector2D(0.33f,0.0f)},// v16
{QVector3D( 1.0f,-1.0f,-1.0f), QVector2D(0.66f,0.0f)},// v17
{QVector3D(-1.0f,-1.0f,1.0f), QVector2D(0.33f,0.5f)},// v18
{QVector3D( 1.0f,-1.0f,1.0f), QVector2D(0.66f,0.5f)},// v19// Vertex data for face 5
{QVector3D(-1.0f,1.0f,1.0f), QVector2D(0.33f,0.5f)},// v20
{QVector3D( 1.0f,1.0f,1.0f), QVector2D(0.66f,0.5f)},// v21
{QVector3D(-1.0f,1.0f,-1.0f), QVector2D(0.33f,1.0f)},// v22
{QVector3D( 1.0f,1.0f,-1.0f), QVector2D(0.66f,1.0f)} // v23
};
// Indices for drawing cube faces using triangle strips.// Triangle strips can be connected by duplicating indices// between the strips. If connecting strips have opposite// vertex order then last index of the first strip and first// index of the second strip needs to be duplicated. If// connecting strips have same vertex order then only last// index of the first strip needs to be duplicated.
GLushort indices[]= {
0,1,2,3,3,// Face 0 - triangle strip ( v0, v1, v2, v3)4,4,5,6,7,7,// Face 1 - triangle strip ( v4, v5, v6, v7)8,8,9,10,11,11,// Face 2 - triangle strip ( v8, v9, v10, v11)12,12,13,14,15,15,// Face 3 - triangle strip (v12, v13, v14, v15)16,16,17,18,19,19,// Face 4 - triangle strip (v16, v17, v18, v19)20,20,21,22,23// Face 5 - triangle strip (v20, v21, v22, v23)
};
// Transfer vertex data to VBO 0
arrayBuf.bind();
arrayBuf.allocate(vertices,24*sizeof(VertexData));
// Transfer index data to VBO 1
indexBuf.bind();
indexBuf.allocate(indices,34*sizeof(GLushort));
}
void GeometryEngine::drawCubeGeometry(QOpenGLShaderProgram*program)
{
// Tell OpenGL which VBOs to use
arrayBuf.bind();
indexBuf.bind();
// Offset for position
quintptr offset =0;
// Tell OpenGL programmable pipeline how to locate vertex position dataint vertexLocation = program->attributeLocation("a_position");
program->enableAttributeArray(vertexLocation);
program->setAttributeBuffer(vertexLocation, GL_FLOAT, offset,3,sizeof(VertexData));
// Offset for texture coordinate
offset +=sizeof(QVector3D);
// Tell OpenGL programmable pipeline how to locate vertex texture coordinate dataint texcoordLocation = program->attributeLocation("a_texcoord");
program->enableAttributeArray(texcoordLocation);
program->setAttributeBuffer(texcoordLocation, GL_FLOAT, offset,2,sizeof(VertexData));
// Draw cube geometry using indices from VBO 1
glDrawElements(GL_TRIANGLE_STRIP,34, GL_UNSIGNED_SHORT,0);
}
