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#include "geometryengine.h"
#include <QVector2D>
#include <QVector3D>
struct VertexData
{
QVector3D position;
QVector2D texCoord;
};
GeometryEngine::GeometryEngine() : vboIds(new GLuint[2])
{
}
GeometryEngine::~GeometryEngine()
{
glDeleteBuffers(2, vboIds);
delete[] vboIds;
}
void GeometryEngine::init()
{
initializeGLFunctions();
//! [0]
// Generate 2 VBOs
glGenBuffers(2, vboIds);
//! [0]
// Initializes cube geometry and transfers it to VBOs
initCubeGeometry();
}
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(-1.0, -1.0, 1.0), QVector2D(0.0, 0.0)}, // v0
{QVector3D( 1.0, -1.0, 1.0), QVector2D(0.33, 0.0)}, // v1
{QVector3D(-1.0, 1.0, 1.0), QVector2D(0.0, 0.5)}, // v2
{QVector3D( 1.0, 1.0, 1.0), QVector2D(0.33, 0.5)}, // v3
// Vertex data for face 1
{QVector3D( 1.0, -1.0, 1.0), QVector2D( 0.0, 0.5)}, // v4
{QVector3D( 1.0, -1.0, -1.0), QVector2D(0.33, 0.5)}, // v5
{QVector3D( 1.0, 1.0, 1.0), QVector2D(0.0, 1.0)}, // v6
{QVector3D( 1.0, 1.0, -1.0), QVector2D(0.33, 1.0)}, // v7
// Vertex data for face 2
{QVector3D( 1.0, -1.0, -1.0), QVector2D(0.66, 0.5)}, // v8
{QVector3D(-1.0, -1.0, -1.0), QVector2D(1.0, 0.5)}, // v9
{QVector3D( 1.0, 1.0, -1.0), QVector2D(0.66, 1.0)}, // v10
{QVector3D(-1.0, 1.0, -1.0), QVector2D(1.0, 1.0)}, // v11
// Vertex data for face 3
{QVector3D(-1.0, -1.0, -1.0), QVector2D(0.66, 0.0)}, // v12
{QVector3D(-1.0, -1.0, 1.0), QVector2D(1.0, 0.0)}, // v13
{QVector3D(-1.0, 1.0, -1.0), QVector2D(0.66, 0.5)}, // v14
{QVector3D(-1.0, 1.0, 1.0), QVector2D(1.0, 0.5)}, // v15
// Vertex data for face 4
{QVector3D(-1.0, -1.0, -1.0), QVector2D(0.33, 0.0)}, // v16
{QVector3D( 1.0, -1.0, -1.0), QVector2D(0.66, 0.0)}, // v17
{QVector3D(-1.0, -1.0, 1.0), QVector2D(0.33, 0.5)}, // v18
{QVector3D( 1.0, -1.0, 1.0), QVector2D(0.66, 0.5)}, // v19
// Vertex data for face 5
{QVector3D(-1.0, 1.0, 1.0), QVector2D(0.33, 0.5)}, // v20
{QVector3D( 1.0, 1.0, 1.0), QVector2D(0.66, 0.5)}, // v21
{QVector3D(-1.0, 1.0, -1.0), QVector2D(0.33, 1.0)}, // v22
{QVector3D( 1.0, 1.0, -1.0), QVector2D(0.66, 1.0)} // 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)
};
//! [1]
// Transfer vertex data to VBO 0
glBindBuffer(GL_ARRAY_BUFFER, vboIds[0]);
glBufferData(GL_ARRAY_BUFFER, 24 * sizeof(VertexData), vertices, GL_STATIC_DRAW);
// Transfer index data to VBO 1
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIds[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 34 * sizeof(GLushort), indices, GL_STATIC_DRAW);
//! [1]
}
//! [2]
void GeometryEngine::drawCubeGeometry(QGLShaderProgram *program)
{
// Tell OpenGL which VBOs to use
glBindBuffer(GL_ARRAY_BUFFER, vboIds[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboIds[1]);
// Offset for position
int offset = 0;
// Tell OpenGL programmable pipeline how to locate vertex position data
int vertexLocation = program->attributeLocation("a_position");
program->enableAttributeArray(vertexLocation);
glVertexAttribPointer(vertexLocation, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void *)offset);
// Offset for texture coordinate
offset += sizeof(QVector3D);
// Tell OpenGL programmable pipeline how to locate vertex texture coordinate data
int texcoordLocation = program->attributeLocation("a_texcoord");
program->enableAttributeArray(texcoordLocation);
glVertexAttribPointer(texcoordLocation, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void *)offset);
// Draw cube geometry using indices from VBO 1
glDrawElements(GL_TRIANGLE_STRIP, 34, GL_UNSIGNED_SHORT, 0);
}
//! [2]
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