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    • By tj8146
      I am using immediate mode for OpenGL and I am creating a 2D top down car game. I am trying to configure my game loop in order to get my car-like physics working on a square shape. I have working code but it is not doing as I want it to. I am not sure as to whether it is my game loop that is incorrect or my code for the square is incorrect, or maybe both! Could someone help because I have been trying to work this out for over a day now
      I have attached my .cpp file if you wish to run it for yourself.. 
      WinMain code:
      /******************* WIN32 FUNCTIONS ***************************/ int WINAPI WinMain( HINSTANCE hInstance, // Instance HINSTANCE hPrevInstance, // Previous Instance LPSTR lpCmdLine, // Command Line Parameters int nCmdShow) // Window Show State { MSG msg; // Windows Message Structure bool done=false; // Bool Variable To Exit Loop Car car; car.x = 220; car.y = 140; car.dx = 0; car.dy = 0; car.ang = 0; AllocConsole(); FILE *stream; freopen_s(&stream, "CONOUT$", "w", stdout); // Create Our OpenGL Window if (!CreateGLWindow("OpenGL Win32 Example",screenWidth,screenHeight)) { return 0; // Quit If Window Was Not Created } while(!done) // Loop That Runs While done=FALSE { if (PeekMessage(&msg,NULL,0,0,PM_REMOVE)) // Is There A Message Waiting? { if (msg.message==WM_QUIT) // Have We Received A Quit Message? { done=true; // If So done=TRUE break; } else // If Not, Deal With Window Messages { TranslateMessage(&msg); // Translate The Message DispatchMessage(&msg); // Dispatch The Message } } else // If There Are No Messages { if(keys[VK_ESCAPE]) done = true; void processKeys(Car& car); //process keyboard while (game_is_running) { loops = 0; while (GetTickCount() > next_game_tick && loops < MAX_FRAMESKIP) { update(car); // update variables next_game_tick += SKIP_TICKS; loops++; } display(car); // Draw The Scene SwapBuffers(hDC); // Swap Buffers (Double Buffering) } } } // Shutdown KillGLWindow(); // Kill The Window return (int)(msg.wParam); // Exit The Program } //WIN32 Processes function - useful for responding to user inputs or other events. LRESULT CALLBACK WndProc( HWND hWnd, // Handle For This Window UINT uMsg, // Message For This Window WPARAM wParam, // Additional Message Information LPARAM lParam) // Additional Message Information { switch (uMsg) // Check For Windows Messages { case WM_CLOSE: // Did We Receive A Close Message? { PostQuitMessage(0); // Send A Quit Message return 0; // Jump Back } break; case WM_SIZE: // Resize The OpenGL Window { reshape(LOWORD(lParam),HIWORD(lParam)); // LoWord=Width, HiWord=Height return 0; // Jump Back } break; case WM_LBUTTONDOWN: { mouse_x = LOWORD(lParam); mouse_y = screenHeight - HIWORD(lParam); LeftPressed = true; } break; case WM_LBUTTONUP: { LeftPressed = false; } break; case WM_MOUSEMOVE: { mouse_x = LOWORD(lParam); mouse_y = screenHeight - HIWORD(lParam); } break; case WM_KEYDOWN: // Is A Key Being Held Down? { keys[wParam] = true; // If So, Mark It As TRUE return 0; // Jump Back } break; case WM_KEYUP: // Has A Key Been Released? { keys[wParam] = false; // If So, Mark It As FALSE return 0; // Jump Back } break; } // Pass All Unhandled Messages To DefWindowProc return DefWindowProc(hWnd,uMsg,wParam,lParam); }  
      C++ and OpenGL code:
      int mouse_x=0, mouse_y=0; bool LeftPressed = false; int screenWidth=1080, screenHeight=960; bool keys[256]; float radiansFromDegrees(float deg) { return deg * (M_PI / 180.0f); } float degreesFromRadians(float rad) { return rad / (M_PI / 180.0f); } bool game_is_running = true; const int TICKS_PER_SECOND = 50; const int SKIP_TICKS = 1000 / TICKS_PER_SECOND; const int MAX_FRAMESKIP = 10; DWORD next_game_tick = GetTickCount(); int loops; typedef struct { float x, y; float dx, dy; float ang; }Car; //OPENGL FUNCTION PROTOTYPES void display(const Car& car); //called in winmain to draw everything to the screen void reshape(int width, int height); //called when the window is resized void init(); //called in winmain when the program starts. void processKeys(Car& car); //called in winmain to process keyboard input void update(Car& car); //called in winmain to update variables /************* START OF OPENGL FUNCTIONS ****************/ void display(const Car& car) { const float w = 50.0f; const float h = 50.0f; glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); glTranslatef(100, 100, 0); glBegin(GL_POLYGON); glVertex2f(car.x, car.y); glVertex2f(car.x + w, car.y); glVertex2f(car.x + w, car.y + h); glVertex2f(car.x, car.y + h); glEnd(); glFlush(); } void reshape(int width, int height) // Resize the OpenGL window { screenWidth = width; screenHeight = height; // to ensure the mouse coordinates match // we will use these values to set the coordinate system glViewport(0, 0, width, height); // Reset the current viewport glMatrixMode(GL_PROJECTION); // select the projection matrix stack glLoadIdentity(); // reset the top of the projection matrix to an identity matrix gluOrtho2D(0, screenWidth, 0, screenHeight); // set the coordinate system for the window glMatrixMode(GL_MODELVIEW); // Select the modelview matrix stack glLoadIdentity(); // Reset the top of the modelview matrix to an identity matrix } void init() { glClearColor(1.0, 1.0, 0.0, 0.0); //sets the clear colour to yellow //glClear(GL_COLOR_BUFFER_BIT) in the display function //will clear the buffer to this colour. } void processKeys(Car& car) { if (keys[VK_UP]) { float cdx = sinf(radiansFromDegrees(car.ang)); float cdy = -cosf(radiansFromDegrees(car.ang)); car.dx += cdx; car.dy += cdy; } if (keys[VK_DOWN]) { float cdx = sinf(radiansFromDegrees(car.ang)); float cdy = -cosf(radiansFromDegrees(car.ang)); car.dx += -cdx; car.dy += -cdy; } if (keys[VK_LEFT]) { car.ang -= 2; } if (keys[VK_RIGHT]) { car.ang += 2; } } void update(Car& car) { car.x += car.dx*next_game_tick; }  
      game.cpp
    • By tj8146
      I am using immediate mode for OpenGL and I am creating a 2D top down car game. I am trying to configure my game loop in order to get my car-like physics working on a square shape. I have working code but it is not doing as I want it to. I am not sure as to whether it is my game loop that is incorrect or my code for the square is incorrect, or maybe both! Could someone help because I have been trying to work this out for over a day now
      I have attached my .cpp file if you wish to run it for yourself.. 
       
      This is my C++ and OpenGL code:
      int mouse_x=0, mouse_y=0; bool LeftPressed = false; int screenWidth=1080, screenHeight=960; bool keys[256]; float radiansFromDegrees(float deg) { return deg * (M_PI / 180.0f); } float degreesFromRadians(float rad) { return rad / (M_PI / 180.0f); } bool game_is_running = true; const int TICKS_PER_SECOND = 50; const int SKIP_TICKS = 1000 / TICKS_PER_SECOND; const int MAX_FRAMESKIP = 10; DWORD next_game_tick = GetTickCount(); int loops; typedef struct { float x, y; float dx, dy; float ang; }Car; //OPENGL FUNCTION PROTOTYPES void display(const Car& car); //called in winmain to draw everything to the screen void reshape(int width, int height); //called when the window is resized void init(); //called in winmain when the program starts. void processKeys(Car& car); //called in winmain to process keyboard input void update(Car& car); //called in winmain to update variables /************* START OF OPENGL FUNCTIONS ****************/ void display(const Car& car) { const float w = 50.0f; const float h = 50.0f; glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); glTranslatef(100, 100, 0); glBegin(GL_POLYGON); glVertex2f(car.x, car.y); glVertex2f(car.x + w, car.y); glVertex2f(car.x + w, car.y + h); glVertex2f(car.x, car.y + h); glEnd(); glFlush(); } void reshape(int width, int height) // Resize the OpenGL window { screenWidth = width; screenHeight = height; // to ensure the mouse coordinates match // we will use these values to set the coordinate system glViewport(0, 0, width, height); // Reset the current viewport glMatrixMode(GL_PROJECTION); // select the projection matrix stack glLoadIdentity(); // reset the top of the projection matrix to an identity matrix gluOrtho2D(0, screenWidth, 0, screenHeight); // set the coordinate system for the window glMatrixMode(GL_MODELVIEW); // Select the modelview matrix stack glLoadIdentity(); // Reset the top of the modelview matrix to an identity matrix } void init() { glClearColor(1.0, 1.0, 0.0, 0.0); //sets the clear colour to yellow //glClear(GL_COLOR_BUFFER_BIT) in the display function //will clear the buffer to this colour. } void processKeys(Car& car) { if (keys[VK_UP]) { float cdx = sinf(radiansFromDegrees(car.ang)); float cdy = -cosf(radiansFromDegrees(car.ang)); car.dx += cdx; car.dy += cdy; } if (keys[VK_DOWN]) { float cdx = sinf(radiansFromDegrees(car.ang)); float cdy = -cosf(radiansFromDegrees(car.ang)); car.dx += -cdx; car.dy += -cdy; } if (keys[VK_LEFT]) { car.ang -= 2; } if (keys[VK_RIGHT]) { car.ang += 2; } } void update(Car& car) { car.x += car.dx*next_game_tick; } My WinMain code:
      /******************* WIN32 FUNCTIONS ***************************/ int WINAPI WinMain( HINSTANCE hInstance, // Instance HINSTANCE hPrevInstance, // Previous Instance LPSTR lpCmdLine, // Command Line Parameters int nCmdShow) // Window Show State { MSG msg; // Windows Message Structure bool done=false; // Bool Variable To Exit Loop Car car; car.x = 220; car.y = 140; car.dx = 0; car.dy = 0; car.ang = 0; AllocConsole(); FILE *stream; freopen_s(&stream, "CONOUT$", "w", stdout); // Create Our OpenGL Window if (!CreateGLWindow("OpenGL Win32 Example",screenWidth,screenHeight)) { return 0; // Quit If Window Was Not Created } while(!done) // Loop That Runs While done=FALSE { if (PeekMessage(&msg,NULL,0,0,PM_REMOVE)) // Is There A Message Waiting? { if (msg.message==WM_QUIT) // Have We Received A Quit Message? { done=true; // If So done=TRUE break; } else // If Not, Deal With Window Messages { TranslateMessage(&msg); // Translate The Message DispatchMessage(&msg); // Dispatch The Message } } else // If There Are No Messages { if(keys[VK_ESCAPE]) done = true; void processKeys(Car& car); //process keyboard while (game_is_running) { loops = 0; while (GetTickCount() > next_game_tick && loops < MAX_FRAMESKIP) { update(car); // update variables next_game_tick += SKIP_TICKS; loops++; } display(car); // Draw The Scene SwapBuffers(hDC); // Swap Buffers (Double Buffering) } } } // Shutdown KillGLWindow(); // Kill The Window return (int)(msg.wParam); // Exit The Program } //WIN32 Processes function - useful for responding to user inputs or other events. LRESULT CALLBACK WndProc( HWND hWnd, // Handle For This Window UINT uMsg, // Message For This Window WPARAM wParam, // Additional Message Information LPARAM lParam) // Additional Message Information { switch (uMsg) // Check For Windows Messages { case WM_CLOSE: // Did We Receive A Close Message? { PostQuitMessage(0); // Send A Quit Message return 0; // Jump Back } break; case WM_SIZE: // Resize The OpenGL Window { reshape(LOWORD(lParam),HIWORD(lParam)); // LoWord=Width, HiWord=Height return 0; // Jump Back } break; case WM_LBUTTONDOWN: { mouse_x = LOWORD(lParam); mouse_y = screenHeight - HIWORD(lParam); LeftPressed = true; } break; case WM_LBUTTONUP: { LeftPressed = false; } break; case WM_MOUSEMOVE: { mouse_x = LOWORD(lParam); mouse_y = screenHeight - HIWORD(lParam); } break; case WM_KEYDOWN: // Is A Key Being Held Down? { keys[wParam] = true; // If So, Mark It As TRUE return 0; // Jump Back } break; case WM_KEYUP: // Has A Key Been Released? { keys[wParam] = false; // If So, Mark It As FALSE return 0; // Jump Back } break; } // Pass All Unhandled Messages To DefWindowProc return DefWindowProc(hWnd,uMsg,wParam,lParam); }  
      game.cpp
    • By lxjk
      Hi guys,
      There are many ways to do light culling in tile-based shading. I've been playing with this idea for a while, and just want to throw it out there.
      Because tile frustums are general small compared to light radius, I tried using cone test to reduce false positives introduced by commonly used sphere-frustum test.
      On top of that, I use distance to camera rather than depth for near/far test (aka. sliced by spheres).
      This method can be naturally extended to clustered light culling as well.
      The following image shows the general ideas

       
      Performance-wise I get around 15% improvement over sphere-frustum test. You can also see how a single light performs as the following: from left to right (1) standard rendering of a point light; then tiles passed the test of (2) sphere-frustum test; (3) cone test; (4) spherical-sliced cone test
       

       
      I put the details in my blog post (https://lxjk.github.io/2018/03/25/Improve-Tile-based-Light-Culling-with-Spherical-sliced-Cone.html), GLSL source code included!
       
      Eric
    • By Fadey Duh
      Good evening everyone!

      I was wondering if there is something equivalent of  GL_NV_blend_equation_advanced for AMD?
      Basically I'm trying to find more compatible version of it.

      Thank you!
    • By Jens Eckervogt
      Hello guys, 
       
      Please tell me! 
      How do I know? Why does wavefront not show for me?
      I already checked I have non errors yet.
      using OpenTK; using System.Collections.Generic; using System.IO; using System.Text; namespace Tutorial_08.net.sourceskyboxer { public class WaveFrontLoader { private static List<Vector3> inPositions; private static List<Vector2> inTexcoords; private static List<Vector3> inNormals; private static List<float> positions; private static List<float> texcoords; private static List<int> indices; public static RawModel LoadObjModel(string filename, Loader loader) { inPositions = new List<Vector3>(); inTexcoords = new List<Vector2>(); inNormals = new List<Vector3>(); positions = new List<float>(); texcoords = new List<float>(); indices = new List<int>(); int nextIdx = 0; using (var reader = new StreamReader(File.Open("Contents/" + filename + ".obj", FileMode.Open), Encoding.UTF8)) { string line = reader.ReadLine(); int i = reader.Read(); while (true) { string[] currentLine = line.Split(); if (currentLine[0] == "v") { Vector3 pos = new Vector3(float.Parse(currentLine[1]), float.Parse(currentLine[2]), float.Parse(currentLine[3])); inPositions.Add(pos); if (currentLine[1] == "t") { Vector2 tex = new Vector2(float.Parse(currentLine[1]), float.Parse(currentLine[2])); inTexcoords.Add(tex); } if (currentLine[1] == "n") { Vector3 nom = new Vector3(float.Parse(currentLine[1]), float.Parse(currentLine[2]), float.Parse(currentLine[3])); inNormals.Add(nom); } } if (currentLine[0] == "f") { Vector3 pos = inPositions[0]; positions.Add(pos.X); positions.Add(pos.Y); positions.Add(pos.Z); Vector2 tc = inTexcoords[0]; texcoords.Add(tc.X); texcoords.Add(tc.Y); indices.Add(nextIdx); ++nextIdx; } reader.Close(); return loader.loadToVAO(positions.ToArray(), texcoords.ToArray(), indices.ToArray()); } } } } } And It have tried other method but it can't show for me.  I am mad now. Because any OpenTK developers won't help me.
      Please help me how do I fix.

      And my download (mega.nz) should it is original but I tried no success...
      - Add blend source and png file here I have tried tried,.....  
       
      PS: Why is our community not active? I wait very longer. Stop to lie me!
      Thanks !
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OpenGL 2D rotations

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Hi all. Just registered! I'm starting out with GLUT and OpenGL and have been playing around. Wrote my own little version of Pong and now I'm moving on to 'Asteroids' But I've got a problem. I'm using the 2D view (gluOrtho2D) but don't know how to rotate something (ie. the spaceship) in 2D. I've rotated things in 3D before whilst learning some of the stuff, but glRotate doesn't seem to work in 2D. Is there a specific command to do this? And if not, how can I go about it? Is there some forumla I can use to calculate new x,y co-ords of a shape based on how much I want to rotate it by? Thanks. [Edited by - BigDogUK on May 27, 2005 3:10:44 AM]

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You could certainly do the calculations yourself. However, AFAIK working with 2d graphics in OpenGL ortho mode is basically just like drawing graphics to the xy plane in 3d. All rotations take place about the z axis, so your rotate calls look like this:

glRotate(angle, 0, 0, 1);

I believe there's a glVertex2(), but no glTranslate2(). So your translation calls will just be:

glTranslate(x, y, 0);

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Ahh, ok. My ship rotates now, but I'm not sure how to set the origin of rotation. It seems to be rotating around 0,0 on my 2D view and fiddling with the:

glRotatef(angle, x, y, 1)

x and y doesn't seem to help. One question. How do the float values correspond to places on a say 800x600 2D view. I'm having trouble working out where things are going to appear which is why I switched to 2DOrtho since it seemed to let me use real co-ords within the window. Ie. 400, 300 is the centre.

Here's my draw code, bit of a mess at the moment since I don't fully understand the viewports, matrix modes etc. Any guidance would be welcome :)

void renderGame(void) {

glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glViewport(0, 0, 760, 480);
glLoadIdentity();
gluOrtho2D(0, 760, 0, 480);
glPushMatrix();
glColor3f(0.0,0.0,0.0); // set bg colour
glBegin(GL_QUADS); // background
glVertex2i(0, 0); // top l
glVertex2i(550, 0); // top r
glVertex2i(550, 400); // bottom r
glVertex2i(0, 400); // bottom l
glEnd();
glColor3f(1.0,1.0,1.0); // set spaceship colour
glRotatef(craftangle, 0, 0, 1);
glBegin(GL_LINE_LOOP); // spacecraft
glVertex2i(260+craftx, 200+crafty); // bottom l
glVertex2i(267+craftx, 224+crafty); // middle
glVertex2i(274+craftx, 200+crafty); // bottom r
glEnd();

glutSwapBuffers();
glPopMatrix();

}

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This:

glRotatef(angle, x, y, 1);

Isn't what you want, but you're doing it correctly in the code below. A couple of other things... You probably need to add glMatrixMode(MODELVIEW) somewhere. And you shouldn't be including your ship's position in the glVertex() calls - use glTranslate() instead. Also, your ship triangle (I assume that's what it is) is currently not centered at the origin. For both those reasons the ship will not behave onscreen as you expect.

Here's your code with a few edits:

glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glViewport(0, 0, 760, 480);
glLoadIdentity();
gluOrtho2D(0, 760, 0, 480);
glPushMatrix(); // Is this doing anything?
glMatrixMode(GL_MODELVIEW); // Added
glLoadIdentity(); // Added
glColor3f(0.0,0.0,0.0); // set bg colour
glBegin(GL_QUADS); // background
glVertex2i(0, 0); // top l
glVertex2i(550, 0); // top r
glVertex2i(550, 400); // bottom r
glVertex2i(0, 400); // bottom l
glEnd();
glColor3f(1.0,1.0,1.0); // set spaceship colour
glTranslatef(ship.x, ship.y, 0); // Added
glRotatef(craftangle, 0, 0, 1);

// You can make this basic shape whatever you want - I
// made it a triangle pointing down the +x axis.
glBegin(GL_LINE_LOOP); // spacecraft
glVertex2i(200, 0); // bottom l
glVertex2i(-200, 200); // middle
glVertex2i(-200, -200); // bottom r
glEnd();

glutSwapBuffers();
glPopMatrix();

Anyway, you might give that a try and see if it behaves any differently.

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Thanks! You've been a great help. I altered my code to your suggestions and it now spins properly on the spot. But I've got one last problem.

At the moment, the spacecraft spins around fine on the spot at the centre where it starts. But when I accelerate it off in a direction and try and rotate it, it still uses the same 0,0 co-ords so the rotation is off again! It's as though its attached to a peice of string connected to 0,0.

Do I need to technically keep it at 0,0 and move view or something? Or is there someway to update the origin it rotates around? Here's my current code:

void renderGame(void) {

glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glViewport(0, 0, 550, 400);
glLoadIdentity();
gluOrtho2D(-225, 225, -200, 200);
glMatrixMode(GL_MODELVIEW); // Added
glLoadIdentity(); // Added
glColor3f(0.0,0.0,0.0); // set bg colour
glBegin(GL_QUADS); // background
glVertex2i(0, 0); // top l
glVertex2i(550, 0); // top r
glVertex2i(550, 400); // bottom r
glVertex2i(0, 400); // bottom l
glEnd();
glColor3f(1.0,1.0,1.0); // set spaceship colour

glRotatef(craftangle, 0, 0, 1);
glTranslatef(craftx, crafty, 0); // Added

glBegin(GL_LINE_LOOP); // spacecraft
glVertex2i(7, -12); // bottom l
glVertex2i(0, 12); // middle
glVertex2i(-7, -12); // bottom r
glEnd();

glutSwapBuffers();
glPopMatrix();

}

Thanks again, Oh and just for the record. I'm not actually altering the craft-x. Does this matter? I'm just altering craft-y to accelerate the craft in the direction it is pointing.

[Edited by - BigDogUK on May 26, 2005 3:14:33 AM]

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Have to leave for work in a moment, but very quickly, you need to put the glTranslate() line before glRotate(), not after. Also, you need to adjust both your ship x and y coordinates, i.e. in world space. You probably need something like this:

ship.y += cos(angle) * speed;
ship.x += sin(angle) * speed; // Or maybe -sin(angle)

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Ok. Thanks!

Been playing around with that and can't seem to get it to move in any logical direction!!! I've tried a few things and I've locked it so the angle is always between 0-360 and the angle of the ship does correspond to the correct rotation.

But it's behaving REALLY erratically. For one, it seems to completetly change direction just by adding or taking one degree from the angle. And it sure as hell isn't moving in the right direction :(

Can anyone have a quick look at my source?

http://www.zen77439.zen.co.uk/other/CurrentAsteroids.cpp

There it is! I don't seem to be doing anything strange and I've tried cleaning up the mix of floats and ints but it doesn't seem to help...

Thanks

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Quote:
But it's behaving REALLY erratically. For one, it seems to completetly change direction just by adding or taking one degree from the angle. And it sure as hell isn't moving in the right direction :(
C++ trig functions take their arguments in radians, not degrees - I suspect that's where your problem lies. You can convert your angles from degrees to radians before submitting them to trig functions by multiplying by pi/180.

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Ahh, I suspected something was off with the angles because I was checking the output of the formula through cout and they were really weird. Sin 90 giving 0.44545 or something. But my knowledge of Maths isn't quite at that level. Getting on to that at A-level hopefully.

Just reworked it and the spaceship moves perfectly! Thanks for all your help :)

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