#168636 - Drovor - Tue May 12, 2009 4:42 pm
I'm new to 3d programming and I'm having some trouble ordering the OpenGL calls properly. I'm hoping I'm doing something obviously wrong with the camera, but I haven't been able to figure it out.
I have implemented 3D picking using the algorithm in the picking demo where I render a 1 pixel viewport around the cursor and check if it changes after each polygon is drawn (genius idea!).
It works 100% when the camera has z<0, but when I start to move my camera around (specifically along the z-axis through the x/y plane) it fails.
Here is all the relevant code (I think!)
Here is my picking code, I'm moving the camera along the Z-axis and when z<0 it works 100%, but when z>0 it doesn't. I think because I'm setting up my camera wrong.
I have implemented 3D picking using the algorithm in the picking demo where I render a 1 pixel viewport around the cursor and check if it changes after each polygon is drawn (genius idea!).
It works 100% when the camera has z<0, but when I start to move my camera around (specifically along the z-axis through the x/y plane) it fails.
Here is all the relevant code (I think!)
| Code: |
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// main loop while (1) { // snip: touch/key handling // these just call glLight light0.set(); light1.set(); glViewport(0,0,255,191); // set the viewport to fullscreen glMatrixMode(GL_PROJECTION); glLoadIdentity(); // this just calls gluPerspective... cam.Perspective() //change cull mode / enable lights glPolyFmt(POLY_ALPHA(31) | POLY_CULL_FRONT | light0.getPolyFmtFlag() | light1.getPolyFmtFlag() | POLY_ID(1)); // Set the current matrix to be the model matrix glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // gluLookAt, location (0,0, variable-z), looking at origin, y=up cam.render(); // draws a grid of quads, essentially a bunch of 3D tiles ug->draw() // This only half works if( held & KEY_TOUCH) ug->pickPoint(touchXY.px, touchXY.py, cam); swiWaitForVBlank(); } |
Here is my picking code, I'm moving the camera along the Z-axis and when z<0 it works 100%, but when z>0 it doesn't. I think because I'm setting up my camera wrong.
| Code: |
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bool UndergroundDrawGrid::pickPoint(int x, int y, Camera &cam) { // This flag makes it so "startCheck" and "endCheck" are called // before and after every polygon is drawn pickMode = true; int viewport[]={0,0,255,191}; // used later for gluPickMatrix() glViewport(0,192,0,192); // set the viewport to fullscreen glMatrixMode(GL_PROJECTION); glLoadIdentity(); // render only what is below the cursor gluPickMatrix(x,(191-y),4,4,viewport); // same perspective as the earlier call cam.Perspective(); glMatrixMode(GL_MODELVIEW); // where do I setup the camera?? It doesn't work at all if I put either of these 2 calls in. // glLoadIdentity(); // cam.render(); // de-select the previously selected object. if (picked) picked->picked = false; // "pickMode" flags will do the magic // using the same draw() function it enables startCheck() and endCheck() to be // called before/after each polygon and save the object which is picked // to "picked" draw(); // if it was hit, mark the new object as picked. // also will mark the old one if a new one wasn't set. if (picked) picked->picked = true; pickMode = false; return endCheck(); } // These are pretty much lifted straight from the picking demo: void UndergroundDrawGrid::startCheck() { while(PosTestBusy()); // wait for the position test to finish while(GFX_BUSY); // wait for all the polygons from the last object to be drawn PosTest_Asynch(0,0,0); // start a position test at the current translated position polyCount = GFX_POLYGON_RAM_USAGE; // save the polygon count } bool UndergroundDrawGrid::endCheck() { while(GFX_BUSY); // wait for all the polygons to get drawn while(PosTestBusy()); // wait for the position test to finish if(GFX_POLYGON_RAM_USAGE>polyCount) // if a polygon was drawn { { // this is currently the closest object under the cursor! closeW=PosTestWresult(); return true; } } return false; } |