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polar01

OpenGL Arcball + translation

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Hi,

I'm trying to create an arcball without playing with the OpenGL API. It is because later I will use it for other kind of API.

My first problem is that I try to translate my object with the mouse, for this I create a plane from my "camera" X axis and the Y axis. Then I project the mouse last position and the current position on this plane. I got 2 3D points and simply use the "difference" between to do my translation.

The problem is that the point I click on the viewport does not exactly follow the mouse.

Here is my code :


if (e->WheelButtonStatus == Down)
{
VNCamera* camera = _surface->GetScene()->GetActiveCamera();

//---- Adapt to viewport size
float lastX = startMouse.x / _surface->GetWidth();
float newY = startMouse.y / _surface->GetHeight();
float newX = ((float)e->x) / _surface->GetWidth();
float lastY = ((float)e->y) / _surface->GetHeight();

//---- Compute the 3D axis
Vector3 axisY = camera->GetEyeUp();
Vector3 axisZ = camera->GetEye() - camera->GetEyeAt();
axisZ = Normalize(axisZ);
Vector3 axisX = Cross(axisY, axisZ);

//---- Projection plane = AxisX + AxisY

// Project mouse on plane
Vector3 lastV;
lastV.x = axisX.x * lastX + axisY.x * lastY;
lastV.y = axisX.y * lastX + axisY.y * lastY;
lastV.z = axisX.z * lastX + axisY.z * lastY;

// Project mouse on plane
Vector3 newV;
newV.x = axisX.x * newX + axisY.x * newY;
newV.y = axisX.y * newX + axisY.y * newY;
newV.z = axisX.z * newX + axisY.z * newY;

//---- Delta
Vector3 delta = newV - lastV;

//---- Adapt the depth
float depth = (camera->GetEye() - camera->GetEyeAt()).Length();
delta *= depth;

//---- Set the camera
Vector3 eye = camera->GetEye() - delta;
Vector3 eyeAt = camera->GetEyeAt() - delta;
camera->SetEye(eye);
camera->SetEyeAt(eyeAt);

//---- Record new mouse position
startMouse.x = e->x;
startMouse.y = e->y;

return;
}


If you have an idea ?

[Edited by - polar01 on December 14, 2010 5:00:49 AM]

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