Problems with gluUnProject
Author
Hello everybody,
I've a grid of Points and I can select it with the mouse.
Now I want to change the y vale of the selected point;
I'm trying to use glUnProject but the the value along the y axis is fake..
This is a piece of my code:
<code>
case WM_MOUSEMOVE:
{
[...]
else if(test == MK_LBUTTON) {
// arrays to hold matrix information
glGetIntegerv(GL_VIEWPORT, viewport_pick);
glGetDoublev(GL_PROJECTION_MATRIX, projection_pick);
glGetDoublev(GL_MODELVIEW_MATRIX, model_view_pick);
// get 3D coordinates based on window coordinates
glReadPixels(
mouse_x, viewport_pick[3]-mouse_y, 5, 5,
GL_DEPTH_COMPONENT, GL_FLOAT, &mouse_z);
gluUnProject(
mouse_x, viewport_pick[3]-mouse_y, mouse_z,
model_view_pick, projection_pick, viewport_pick,
&pos3D_x, &pos3D_y, &pos3D_z);
if(SOME_SELECTED) {
for(int i = 0; i < 4; i++) {
if(indexes != -1) {
setGridVertexHeight(indexes, pos3D_y);
}
}
}
}
</code>
Someone could suggest me a solution? The y value result too small (e.g. 0.013).
Could be a problem in the glReadPixels?
Thanks anyway!
Chri
I think you should separate the selecting/moving code from the windproc callback function. Maybe the matrices are reseted at that state.
And an other thing, you read 5x5 pixels, but maybe your mouse_z value is just a single float, so you overwrite memory, where you shouldn't, read 1x1, that's legal.
and
And an other thing, you read 5x5 pixels, but maybe your mouse_z value is just a single float, so you overwrite memory, where you shouldn't, read 1x1, that's legal.
and
<br><br>edit: and I don't see, where you convert the world x,y,z coordinates to index of the array? Or using openGl selecting mechanism?<br><br><!--EDIT--><span class=editedby><!--/EDIT-->[Edited by - szecs on August 17, 2009 2:41:00 AM]<!--EDIT--></span><!--/EDIT-->
Author
First of all thanks for the answer and the suggestions :)
I call the selection function when left mouse button is pressed:
This is a part of the selection()
Maybe you can see something of wrong?
Chri
I call the selection function when left mouse button is pressed:
case WM_LBUTTONDOWN:{ mouse_x = LOWORD(lParam); mouse_y = HIWORD(lParam); Selection();}return 0;This is a part of the selection()
void Selection() { GLfloat fAspect; // Space for selection buffer static GLuint selectBuff[BUFFER_LENGTH]; // Hit counter and viewport storage GLint hits, viewport[4]; // Set up selection buffer glSelectBuffer(BUFFER_LENGTH, selectBuff); // Get the viewport glGetIntegerv(GL_VIEWPORT, viewport); // Switch to projection and save the matrix glMatrixMode(GL_PROJECTION); glPushMatrix(); // Change render mode glRenderMode(GL_SELECT); // Establish new clipping volume to be unit cube around // mouse cursor point (xPos, yPos) and extending two pixels // in the vertical and horizontal direction glLoadIdentity(); gluPickMatrix(mouse_x, viewport[3] - mouse_y + viewport[1], 3,3, viewport); // Apply perspective matrix fAspect = (float)viewport[2] / (float)viewport[3]; gluPerspective(45.0f, fAspect, 1.0, 425.0); //Draw the scene RenderScene(); // Collect the hits hits = glRenderMode(GL_RENDER); if (hits > 1) {[...] // Restore the projection matrix glMatrixMode(GL_PROJECTION); glPopMatrix(); // Go back to modelview for normal rendering glMatrixMode(GL_MODELVIEW);}Maybe you can see something of wrong?
Chri
I think you could easily debug the selection part by outputting the selected vertex index. It was long, since I used selecting, but I miss some things in your code, for exaple:
It was long ago, so try to get more info about using this.
And the 5x5 depth values loaded into a single float is still an issue I think
glInitNames();glPushName(0);//in selection function...glLoadName(i); // in render scene (maybe you have this) i: index of vertexIt was long ago, so try to get more info about using this.
And the 5x5 depth values loaded into a single float is still an issue I think
Author
Hi,
I've corrected the 5x5 issue but my problem persist.
This is my render scene:
As you can see
glInitNames();
glPushName(0);
are there.
In DrawGrid() i do the glLoadName().
The selection works fine, the problem is the glUnProject() that doesn't work. It give me value too small for the y axis.
I've corrected the 5x5 issue but my problem persist.
This is my render scene:
int RenderScene(void) { // Clear the window with current clearing color glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Save the matrix state and do the rotations glMatrixMode(GL_MODELVIEW); glPushMatrix();[...] DrawGrid(); // Initialize the names stack glInitNames(); glPushName(0);[...] // Restore the matrix state glPopMatrix(); // Modelview matrix return TRUE;}As you can see
glInitNames();
glPushName(0);
are there.
In DrawGrid() i do the glLoadName().
The selection works fine, the problem is the glUnProject() that doesn't work. It give me value too small for the y axis.
Do you update the mouse's coordinates in WM_MOUSEMOVE while l_button is pressed?
If yes, than I have no idea.
If yes, than I have no idea.
glReadPixels could still be an issue depending on where the cursor read position is set. Make sure to at least use setCursorPos before reading pixels. Also you might need to adjust some read settings in GL.
Then I would recommend to create a test scenario with a rectangle and use glUnProject to create a ray from the mouse click and do an intersection test with the rectangle (google for ray-plane intersection test). Then you would get the actual intersection point in 3d which you can then gluProject to get the Z value you should actually also get from glReadPixels.
Then you can come back with the results which might point to what is going wrong.
Then I would recommend to create a test scenario with a rectangle and use glUnProject to create a ray from the mouse click and do an intersection test with the rectangle (google for ray-plane intersection test). Then you would get the actual intersection point in 3d which you can then gluProject to get the Z value you should actually also get from glReadPixels.
Then you can come back with the results which might point to what is going wrong.
Author
Quote:
Do you update the mouse's coordinates in WM_MOUSEMOVE while l_button is pressed?
If yes, than I have no idea.
Yes the coord are updated..I have no idea too
Quote:
I would recommend to create a test scenario
Ok I'll try..this is my last hope
Thanks guys
This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement
