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polar01

OpenGL Screen to 3D space - for picking

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Hi,

I'm currently working on a picking algorithm WITHOUT OpenGL !
The algorithm work fine, but I have problem to transform the mouse X,Y into a "3D ray" for the picking.

To test, I have try with OpenGL like this (but it doesn't work !!)

glMatrixMode(GL_PROJECTION); // Set up the projection
glLoadIdentity();

float aspectRatio = ((float)surface->GetWidth()) / surface->GetHeight();
gluPerspective(45, aspectRatio, 0.1f, 10000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(
camera->GetEye().x, camera->GetEye().y, camera->GetEye().z,
camera->GetEyeAt().x, camera->GetEyeAt().y, camera->GetEyeAt().z,
camera->GetEyeUp().x, camera->GetEyeUp().y, camera->GetEyeUp().z);

double matModel[16];
double matProj[16];
GLint viewport[4];

glGetDoublev(GL_PROJECTION_MATRIX, matProj);
glGetDoublev(GL_MODELVIEW_MATRIX, matModel);
glGetIntegerv(GL_VIEWPORT, viewport);
GLdouble o[3];
GLdouble t[3];
gluUnProject ( x, surface->GetHeight() - y, 0.0, matModel, matProj, viewport, &o[0], &o[1], &o[2]);
gluUnProject ( x, surface->GetHeight() - y, 1.0, matModel, matProj, viewport, &t[0], &t[1], &t[2]);

out->o.x = o[0];
out->o.y = o[1];
out->o.z = o[2];

out->d.x = t[0] - o[0];
out->d.y = t[1] - o[1];
out->d.z = t[2] - o[2];

out->d = Normalize(out->d);


The problem is that I cannot use OpenGL, so I have this code :


//--- Get the camera axis
VNCamera* camera = surface->GetScene()->GetActiveCamera();
Vector3 eye = camera->GetEye();
Vector3 eyeAt = camera->GetEyeAt();
Vector3 axisz = Normalize(eyeAt - eye);
Vector3 axisy = camera->GetEyeUp();

Vector3 axisx = Cross(axisz, axisy);

//---- Origin
out->o = eye;

//---- Direction
// Project mouse to space
float fx = x;
float fy = surface->GetHeight() - 1.f - y;

// Normalize to [-1 , 1]
fx /= surface->GetHeight();
fy /= surface->GetHeight();

fx -= 0.5f;
fy -= 0.5f;

fx *= 2;
fy *= 2;

// Adapt for FOV
float fovInRadians = 45.f * (M_PI / 180.0f);
fx *= tanf(fovInRadians);

// Project the mouse coordinate on the Z-far-plane
out->d.x = axisx.x * fx + axisy.x * fy + eyeAt.x;
out->d.y = axisx.y * fx + axisy.y * fy + eyeAt.x;
out->d.z = axisx.z * fx + axisy.z * fy + eyeAt.x;

// Compute the direction
out->d = out->d - eye;
out->d = Normalize(out->d);

out->mint = 0;
out->maxt = INFINITY;


I'm unable to find the problem with the last code, in order to pick in an OpenGL windows ! So, if you have an idea ?

Thx

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