How to rotate this mesh correctly?-CodePudding

The

planeXY.setupMesh(); planeXY1.setupMesh(); planeXY1.modelMatrix.translate(QVector3D(0.0, 0.0, 2.0)); planeZY.setupMesh(); planeZY.modelMatrix.rotate(-90.0f, QVector3D(0.0f, 1.0f, 0.0f)); planeZY1.setupMesh(); planeZY1.modelMatrix.translate(QVector3D(2.0, 0.0, 0.0)); planeZY1.modelMatrix.rotate(-90.0f, QVector3D(0.0f, 1.0f, 0.0f)); planeXZ.setupMesh(); planeXZ.modelMatrix.rotate(90.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeXZ1.setupMesh(); planeXZ1.modelMatrix.translate(QVector3D(0.0, 2.0, 0.0)); planeXZ1.modelMatrix.rotate(90.0f, QVector3D(1.0f, 0.0f, 0.0f));

Plane generation

Mesh CreateMeshPlane(Vector3D bottomleft, size_t numvertices_x, size_t numvertices_y, size_t worldsize_x, size_t worldsize_y) { Mesh mesh; int numVerts = numvertices_x * numvertices_y; int numFaces = (numvertices_x - 1) * (numvertices_y - 1); int numIndices = numFaces * 6; float xStep = (float)worldsize_x / (numvertices_x - 1); float yStep = (float)worldsize_y / (numvertices_y - 1); mesh.vertices.resize(numVerts); mesh.indices.resize(numIndices); for (size_t y = 0; y < numvertices_y; y ) { for (size_t x = 0; x < numvertices_x; x ) { mesh.vertices[x (y * numvertices_x)] = QVector3D(bottomleft.x() (xStep * x), bottomleft.y() (yStep * y), bottomleft.z()); } } int offset = 0; for (int i = 0; i < numIndices; i =6) { unsigned int cornerIndex = i/6 offset; if ((cornerIndex 1)%numvertices_x == 0) { offset ; cornerIndex ; } // First triangle int idx = 0; Face face; face.FaceIndices.resize(6); face.Edges.push_back(Edge((unsigned int)cornerIndex, (unsigned int)cornerIndex numvertices_x)); face.FaceIndices[idx] = (unsigned int)cornerIndex;/*0*/ idx ; face.FaceIndices[idx] = (unsigned int)cornerIndex numvertices_x; /*3*/ idx ; face.Edges.push_back(Edge((unsigned int)cornerIndex numvertices_x, (unsigned int)cornerIndex numvertices_x 1)); face.FaceIndices[idx] = (unsigned int)cornerIndex numvertices_x 1; /*4*/ idx ; // Second triangle face.FaceIndices[idx] = (unsigned int)cornerIndex; face.Edges.push_back(Edge((unsigned int)cornerIndex, (unsigned int)cornerIndex 1)); idx ; face.FaceIndices[idx] = (unsigned int)cornerIndex numvertices_x 1; idx ; face.Edges.push_back(Edge((unsigned int)cornerIndex numvertices_x 1, (unsigned int)cornerIndex 1)); face.FaceIndices[idx] = (unsigned int)cornerIndex 1; mesh.faces.push_back(face); } return mesh; }

Creating planes

planeXZ = CreateMeshPlane({0.0, 0.0, 0.0}, ny, nx, 2, 2); planeXZ1 = CreateMeshPlane({0.0, 0.0, 0.0}, ny, nx, 2, 2); planeXY = CreateMeshPlane({0.0, 0.0, 0.0}, ny, nz, 2, 2); planeXY1 = CreateMeshPlane({0.0, 0.0, 0.0}, ny, nz, 2, 2); planeZY = CreateMeshPlane({0.0,0.0,0.0}, nx, nz, 2, 2); planeZY1 = CreateMeshPlane({0.0, 0.0,0.0}, nx, nz, 2, 2);

Then i try to rotate all planes around X axis. My code

if(ev->key() == Qt::Key_R) { planeXY.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeXY1.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeZY.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeZY1.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeXZ.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); planeXZ1.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); }

Result:

We can see that each plane rotates around its own X axes, how to rotate all planes around global X axis

CodePudding user response：

I think qt and opengl does matrix multiplication from right to left, so the order

planeXY1.modelMatrix.translate(QVector3D(0.0, 0.0, 2.0)); planeXY.modelMatrix.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f));

actually does the 20 degree rotate then the translate. I think you want translate then the rotate to happen, so maybe reverse the order of the matrices and see if that helps.

CodePudding user response：

In your keyboard event you need to apply the rotation from the other side. So your code should look similar to this:

if(ev->key() == Qt::Key_R) { QMatrix4x4 mat; //mat.translate(rotationCenter.x, rotationCenter.y, rotationCenter.z); mat.rotate(20.0f, QVector3D(1.0f, 0.0f, 0.0f)); //mat.translate(-rotationCenter.x, -rotationCenter.y, -rotationCenter.z); planeXY.modelMatrix = mat * planeXY.modelMatrix; planeXY1.modelMatrix = mat * planeXY1.modelMatrix; planeZY.modelMatrix = mat * planeZY.modelMatrix; planeZY1.modelMatrix = mat * planeZY1.modelMatrix; planeXZ.modelMatrix = mat * planeXZ.modelMatrix; planeXZ1.modelMatrix = mat * planeXZ1.modelMatrix; }

(I never used Qt so far so there might be some typos inside.)

When you do no want to rotate about the origin of world space you need the 2 translations which are commented out.