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Selection not working
April 15, 2002 05:46 PM
Hi. I am trying to incorporate picking into a program of mine for the first time. I have stayed pretty close to NeHes stuff, but it''s still not working. I am storing the resulting id in a variable "Selection" and outputting that to the screen to see whether its working. The only reponse I get is 0, or no response at all.
The relevant code is as follows... Please let me know where I am going wrong - I have tried a variety of things from various places but they dont seem to work.
GLuint buffer[512];
GLint intersections=0;
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
glSelectBuffer(512, buffer);
(void) glRenderMode(GL_SELECT);
glInitNames();
glPushName(0);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluPickMatrix((GLdouble) (WinWidth-mpos.x), (GLdouble) (WinHeight-mpos.y), 1.0f, 1.0f, viewport);
glOrtho(0.0f,WinWidth,WinHeight,0.0f,-1.0f,1.0f);
glMatrixMode(GL_MODELVIEW);
{
LoadIdentity();
for (int j = 0; j < Props.PropNumber+1; j++)
{
PushMatrix();
LoadName(j);
glTranslatef (Props.current[j].Position[0]+(float)x_move,Props.current[j].Position[1]+(float)y_move,0);
glRotatef((float)Props.current[j].Rotation, 0.0f, 0.0f, 1);
glBegin (GL_POLYGON);
for (int i = 0; i < Props.current[j].FrameCoords; i++)
{
glVertex2f(Props.current[j].PlaceHolder[0]-(float)Props.current[j].HDis,//+x_move,
Props.current[j].PlaceHolder[1]-(float)Props.current[j].VDis);//+y_move);
}
glEnd();
PopMatrix();
}
}
intersections=glRenderMode(GL_RENDER);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
if (intersections > 0)
{
int choose = buffer[3];
int depth = buffer[1];
for (int loop = 1; loop < intersections; loop++)
{
if (buffer[loop*4+1] < GLuint(depth))
{
choose = buffer[loop*4+3];
depth = buffer[loop*4+1];
}
}
Selection = choose;
}
Also, the glOrtho line… I assume it should be the same as how it is defined in the ReshapeGL proc? I believe I have it wrong in both places (it should be "glOrtho(0.0f,WinWidth,0.0f,WinHeight,-1.0f,1.0f);" yes?), I have tried correcting it but the only difference that makes is that everything goes upside down.
Any help would be greatly appreciated.
Thanks, Dy </i>
308
April 17, 2002 07:47 PM
I''d suggest that you go
I''m not sure why, but thats how I am doing it:
" Do we need us? "
glMatrixMode(GL_PROJECTION);glPopMatrix();glMatrixMode(GL_MODELVIEW);intersections=glRenderMode(GL_RENDER); I''m not sure why, but thats how I am doing it:
GLuint buffer[512]; // Set Up A Selection Buffer GLint hits; // The Number Of Objects That We Selected // The Size Of The Viewport. [0] Is <x>, [1] Is <y>, [2] Is <length>, [3] Is <width> GLint viewport[4]; // This Sets The Array <viewport> To The Size And Location Of The Screen Relative To The Window glGetIntegerv(GL_VIEWPORT, viewport); glSelectBuffer(512, buffer); // Tell OpenGL To Use Our Array For Selection (void) glRenderMode(GL_SELECT); glInitNames(); // Initializes The Name Stack glPushName(0); // Push 0 (At Least One Entry) Onto The Stack // Puts OpenGL In Selection Mode. Nothing Will Be Drawn. Object ID''s and Extents Are Stored In The Buffer. glMatrixMode(GL_PROJECTION); // Selects The Projection Matrix glPushMatrix(); // Push The Projection Matrix glLoadIdentity(); // Resets The Matrix // This Creates A Matrix That Will Zoom Up To A Small Portion Of The Screen, Where The Mouse Is. gluPickMatrix((GLdouble) x, (GLdouble) (viewport[3]-y), 1.0f, 1.0f, viewport); // Apply The Perspective Matrix gluPerspective(45.0f, (GLfloat) (viewport[2]-viewport[0])/(GLfloat) (viewport[3]-viewport[1]), 0.1f, 100.0f); glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix // Draw one anchor for (int i = 0; i<lib.GetSize(); i++) { if(lib.Get(i) !=NULL) lib.Get(i)->Draw(); } //patch1.Draw(); glMatrixMode(GL_PROJECTION); // Select The Projection Matrix glPopMatrix(); // Pop The Projection Matrix glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix hits=glRenderMode(GL_RENDER); // Switch To Render Mode, Find Out How Many if (hits>0) // If There Were More Than 0 Hits { SelectedObj = buffer[3]; for (int i=0; i<lib.GetSize(); i++) { if( lib.Get(i)->GetID() == SelectedObj) { lib.Get(i)->Picked = true; if(strcmp(lib.Get(i)->GetName(),"BPatch") == 0) { EditMaterial.ShowWindow(SW_SHOW); EditMaterial.SetMaterial( &((CBezierPatch *)lib.Get(i))->m_material); EditMaterial.CheckRadioButton(ID_MAT_AMBIENT, ID_MAT_SPECULAR, ID_MAT_AMBIENT); } ObjProp.SetObject(GetObjSel(&lib)); } } } " Do we need us? "
" Do we need us? "Ionware Productions - Games and Game Tools Development
April 19, 2002 12:19 PM
Thanks for the response!
I tried that and it didnt seem to make too much difference. However, while testing it, I noticed that the screen seemed reversed so I changed the
glOrtho(0.0f,WinWidth,WinHeight,0.0f,-1.0f,1.0f);
line to
glOrtho(WinWidth,0.0f,WinHeight,0.0f,-1.0f,1.0f);
and now it seems to be working ok. Not entirely sure why, but there you go...
Dy
I tried that and it didnt seem to make too much difference. However, while testing it, I noticed that the screen seemed reversed so I changed the
glOrtho(0.0f,WinWidth,WinHeight,0.0f,-1.0f,1.0f);
line to
glOrtho(WinWidth,0.0f,WinHeight,0.0f,-1.0f,1.0f);
and now it seems to be working ok. Not entirely sure why, but there you go...
Dy
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