[英]How do I draw a simple line in Qt3D?
從您鏈接的視頻中,我想到了下面的代碼(也發布在Qt論壇中: https : //forum.qt.io/topic/66808/qt3d-draw-grid-axis-lines/3 )。
首先,您需要創建QGeometry。 因為它是一條簡單的線,所以它僅由2個頂點(起點,終點)和2個索引(鏈接這些頂點)組成。 為此,您需要創建2個QByteArray並將其存儲到QBuffer中。 在第一個中,存儲2個頂點(每個頂點的x,y和z坐標)。 在第二個中,您只是說您想將第一個頂點鏈接到第二個。 當我們在渲染器上使用Qt3DRender::QGeometryRenderer::Lines
時,僅需要2個索引。
完成后,只需將QGeometry放入QGeometryRenderer中即可擁有網格,然后將其放入QEntity中,使其出現在樹中並進行渲染。
#include <Qt3DCore/QEntity>
#include <Qt3DCore/QTransform>
#include <Qt3DExtras/QPhongMaterial>
#include <Qt3DRender/QAttribute>
#include <Qt3DRender/QBuffer>
#include <Qt3DRender/QGeometry>
void drawLine(const QVector3D& start, const QVector3D& end, const QColor& color, Qt3DCore::QEntity *_rootEntity)
{
auto *geometry = new Qt3DRender::QGeometry(_rootEntity);
// position vertices (start and end)
QByteArray bufferBytes;
bufferBytes.resize(3 * 2 * sizeof(float)); // start.x, start.y, start.end + end.x, end.y, end.z
float *positions = reinterpret_cast<float*>(bufferBytes.data());
*positions++ = start.x();
*positions++ = start.y();
*positions++ = start.z();
*positions++ = end.x();
*positions++ = end.y();
*positions++ = end.z();
auto *buf = new Qt3DRender::QBuffer(geometry);
buf->setData(bufferBytes);
auto *positionAttribute = new Qt3DRender::QAttribute(geometry);
positionAttribute->setName(Qt3DRender::QAttribute::defaultPositionAttributeName());
positionAttribute->setVertexBaseType(Qt3DRender::QAttribute::Float);
positionAttribute->setVertexSize(3);
positionAttribute->setAttributeType(Qt3DRender::QAttribute::VertexAttribute);
positionAttribute->setBuffer(buf);
positionAttribute->setByteStride(3 * sizeof(float));
positionAttribute->setCount(2);
geometry->addAttribute(positionAttribute); // We add the vertices in the geometry
// connectivity between vertices
QByteArray indexBytes;
indexBytes.resize(2 * sizeof(unsigned int)); // start to end
unsigned int *indices = reinterpret_cast<unsigned int*>(indexBytes.data());
*indices++ = 0;
*indices++ = 1;
auto *indexBuffer = new Qt3DRender::QBuffer(geometry);
indexBuffer->setData(indexBytes);
auto *indexAttribute = new Qt3DRender::QAttribute(geometry);
indexAttribute->setVertexBaseType(Qt3DRender::QAttribute::UnsignedInt);
indexAttribute->setAttributeType(Qt3DRender::QAttribute::IndexAttribute);
indexAttribute->setBuffer(indexBuffer);
indexAttribute->setCount(2);
geometry->addAttribute(indexAttribute); // We add the indices linking the points in the geometry
// mesh
auto *line = new Qt3DRender::QGeometryRenderer(_rootEntity);
line->setGeometry(geometry);
line->setPrimitiveType(Qt3DRender::QGeometryRenderer::Lines);
auto *material = new Qt3DExtras::QPhongMaterial(_rootEntity);
material->setAmbient(color);
// entity
auto *lineEntity = new Qt3DCore::QEntity(_rootEntity);
lineEntity->addComponent(line);
lineEntity->addComponent(material);
}
這分別是我對緩沖區類型必須做的更正(我現在假定其已棄用):
auto *buf = new Qt3DRender::QBuffer(Qt3DRender::QBuffer::VertexBuffer, geometry);
auto *indexBuffer = new Qt3DRender::QBuffer(Qt3DRender::QBuffer::IndexBuffer, geometry);
我的是Win 10的Qt 5.9。
我建議看一下https://doc-snapshots.qt.io/qt5-5.9/qt3d-basicshapes-cpp-example.html ,不久前我問自己一個類似的問題,即如何畫圓。 好吧,3D圓是一個圓環,其半徑比例特殊:
// thin Torus = Circle in 3D
Qt3DCore::QEntity *torusEntity0 = new Qt3DCore::QEntity(rootEntity);
Qt3DExtras::QTorusMesh *torusMesh0 = new Qt3DExtras::QTorusMesh;
torusMesh0->setRadius(15);
torusMesh0->setMinorRadius(0.01f);
torusMesh0->setRings(100);
torusMesh0->setSlices(20);
torusEntity0->addComponent(torusMesh0);
torusEntity0->addComponent(material);
那么3D線是什么? 這將是具有非常小的外半徑的圓柱體。
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