Having a problem with selection of objects.
Ultimately, I want to be able to right-click on an object, which results in pop up messagewindow with a list of moves the object can make (checkers prog)
I thought I had a pretty good understanding of how selection works (via select_mode). However, I'm not getting any results.
This was from an example on the internet.Code :int RetrieveObjectID(int x, int y) { int objectsFound = 0; // This will hold the amount of objects clicked int viewportCoords[4] = {0}; // We need an array to hold our view port coordinates // This will hold the ID's of the objects we click on. unsigned int selectBuffer[32] = {0}; // glSelectBuffer is what we register our selection buffer with. The first parameter // is the size of our array. The next parameter is the buffer to store the information found. // More information on the information that will be stored in selectBuffer is further below. glSelectBuffer(32, selectBuffer); // Setup our selection buffer to accept object ID's // This function returns information about many things in OpenGL. We pass in GL_VIEWPORT // to get the view port coordinates. It saves it like a RECT with {top, left, bottom, right} glGetIntegerv(GL_VIEWPORT, viewportCoords); // Get the current view port coordinates // Now we want to get out of our GL_MODELVIEW matrix and start effecting our // GL_PROJECTION matrix. This allows us to check our X and Y coords against 3D space. glMatrixMode(GL_PROJECTION); // We want to now effect our projection matrix glPushMatrix(); // We push on a new matrix so we don't effect our 3D projection glRenderMode(GL_SELECT); // Allows us to render the objects, but not change the frame buffer glLoadIdentity(); // Reset our projection matrix gluPickMatrix(x, viewportCoords[3] - y, 2, 2, viewportCoords); cout<< x << " x value, " << viewportCoords[3] - y << " y value, "<< 2 << " " << 2 <<endl; // Next, we just call our normal gluPerspective() function, exactly as we did on startup. // This is to multiply the perspective matrix by the pick matrix we created up above. gluPerspective(45.0f,(float)g_rRect.right/(float)g_rRect.bottom,1.0f,300.0f); glMatrixMode(GL_MODELVIEW); // Go back into our model view matrix glutDisplay(); // Now we render into our selective mode to pinpoint clicked objects objectsFound = glRenderMode(GL_RENDER); // Return to render mode and get the number of objects found glMatrixMode(GL_PROJECTION); // Put our projection matrix back to normal. glPopMatrix(); // Stop effecting our projection matrix glMatrixMode(GL_MODELVIEW); // Go back to our normal model view matrix if (objectsFound > 0) { // Set the lowest depth to the first object to start it off. // 1 is the first object's minimum Z value. // We use an unsigned int so we don't get a warning with selectBuffer below. unsigned int lowestDepth = selectBuffer[1]; // Set the selected object to the first object to start it off. // 3 is the first object's object ID we passed into glLoadName(). int selectedObject = selectBuffer[3]; // Go through all of the objects found, but start at the second one for(int i = 1; i < objectsFound; i++) { // Check if the current objects depth is lower than the current lowest // Notice we times i by 4 (4 values for each object) and add 1 for the depth. if(selectBuffer[(i * 4) + 1] < lowestDepth) { // Set the current lowest depth lowestDepth = selectBuffer[(i * 4) + 1]; // Set the current object ID selectedObject = selectBuffer[(i * 4) + 3]; } } // Return the selected object return selectedObject; } // We didn't click on any objects so return 0 return 0; }
Its called from the GlutMouse function.
Also here's the display function i use
My only guesses of whats wrong is maybe my selection buffer is too small, I read somewhere that it holds all kinds of info on objects and I have 24 pieces which are to be selected. Also would the transformations I do before created the object have anything do with it?Code :void glutDisplay(void) { glDisable(GL_LIGHTING); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glClearColor(1.0,1.0,1.0,1.0); if (wireframe) glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); else glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); glPushMatrix(); /* translate camera to the coordinates provided by eye array */ glTranslatef (-eye[0], -eye[1], -eye[2]); /* rotates the screen by the angles provided by rot array */ glRotatef(rot[0], 1.0f, 0.0f, 0.0f); glRotatef(rot[1], 0.0f, 1.0f, 0.0f); glRotatef(rot[2], 0.0f, 0.0f, 1.0f); glBindTexture(GL_TEXTURE_2D, g_TexturesArray[0]); //**** Call display list for checker board glCallList(displayLists); glPopMatrix(); for(int i = 0; i < 12; i++) { if(Piece_Alive[1][i] == true) { double dimX, dimY; glPushName(i + 100); glPushMatrix(); /* translate camera to the coordinates provided by eye array */ glTranslatef (-eye[0], -eye[1], -eye[2]); /* rotates the screen by the angles provided by rot array */ glRotatef(rot[0], 1.0f, 0.0f, 0.0f); glRotatef(rot[1], 0.0f, 1.0f, 0.0f); glRotatef(rot[2], 0.0f, 0.0f, 1.0f); // We translate the cylinder over by half of it's length so it's centered on the screen glColor3f(0.1f,0.1f,0.1f); getCoordinateValues(dimX, dimY, Piece_CoordinateX[i], Piece_CoordinateY[i]); // cout << dimX << " x value "<< dimY <<" y value "<<endl; glTranslatef(dimX - 1, 1.11, dimY +.25); // Move the cylinder over so it's centered around (0, 0, 0) glRotatef(90, 1.0f, 0.0f, 0.0f); glCallList(displayLists + 1); glPopMatrix(); glPopName(); } } for(int j = 12; j < 24; j++) { if(Piece_Alive[0][j] == true) { double dimX, dimY; glPushName(j + 100); glPushMatrix(); /* translate camera to the coordinates provided by eye array */ glTranslatef (-eye[0], -eye[1], -eye[2]); /* rotates the screen by the angles provided by rot array */ glRotatef(rot[0], 1.0f, 0.0f, 0.0f); glRotatef(rot[1], 0.0f, 1.0f, 0.0f); glRotatef(rot[2], 0.0f, 0.0f, 1.0f); // We translate the cylinder over by half of it's length so it's centered on the screen glColor3f(1.0f,0.0f,0.0f); getCoordinateValues(dimX, dimY, Piece_CoordinateX[j], Piece_CoordinateY[j]); // cout << dimX << " x value "<< dimY <<" y value "<<endl; glTranslatef(dimX - 1, 1.11, dimY - 2.25); // Move the cylinder over so it's centered around (0, 0, 0) glRotatef(90, 1.0f, 0.0f, 0.0f); glCallList(displayLists + 1); glPopMatrix(); glPopName(); } } CalculateFrameRate(); glFlush(); glutSwapBuffers(); }
