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Diffstat (limited to 'examples/opengl/cube/geometryengine.cpp')
| -rw-r--r-- | examples/opengl/cube/geometryengine.cpp | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/examples/opengl/cube/geometryengine.cpp b/examples/opengl/cube/geometryengine.cpp new file mode 100644 index 0000000000..2f6f65948d --- /dev/null +++ b/examples/opengl/cube/geometryengine.cpp @@ -0,0 +1,130 @@ +#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() +{ +//! [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] |