Tetris block rotates wrong way?

This is a discussion on Tetris block rotates wrong way? within the Game Programming forums, part of the General Programming Boards category; This is how a normal block should rotate, right? Code: xx xx becomes x xx x but mine becomes Code: ...

  1. #1
    Registered User Kenoriga's Avatar
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    Singapore
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    Angry Tetris block rotates wrong way?

    This is how a normal block should rotate, right?
    Code:
     xx
    xx
    
    becomes
    
    x
    xx
     x
    but mine becomes
    Code:
     x
    xx
    x
    instead.

    This is the code
    Code:
    void display()
    {float xmov = 3.0f;
    float ymov = 3.0f;
    float anrot = 0.0f;
    float yrot = 0.0f;
    float xrot = 0.0f;
    
    
    	glClear(GL_COLOR_BUFFER_BIT);
    	
        
        glPushMatrix();
    	    glScalef(0.2f, 0.2f, 0.0f);
            glTranslatef(xmov, ymov, 0.0f);
            glRotatef(anrot, xrot, yrot, 1.0f);
    		glColor3f(0.5f, 0.5f, 1.0f);
    		
    		glBegin(GL_QUADS);          
                glVertex2f(-0.1f, -0.1f);
                glVertex2f(-0.1f, 0.0f);
                glVertex2f(0.0f, 0.0f);
                glVertex2f(0.0f, -0.1f);
            glEnd();
            
            glBegin(GL_QUADS);
                glVertex2f(-0.1f, 0.0f);
                glVertex2f(-0.1f, 0.1f);
                glVertex2f(0.0f, 0.1f);
                glVertex2f(0.0f, 0.0f);
            glEnd();
            
            glBegin(GL_QUADS);
                glVertex2f(0.0f, 0.0f);
                glVertex2f(0.0f, 0.2f);
                glVertex2f(0.1f, 0.2f);
                glVertex2f(0.1f, 0.0f);
            glEnd();
            
            
        glPopMatrix();
            
    	glFlush();
    
    }
    
    void idle()
    {   if (xmov < 0.0f)
        {xmov = 5.0f;}
        if (ymov < 0.0f)
        {ymov = 5.0f;}
    }
    
    LRESULT OpenGL::WndProc(HWND hwnd, UINT msg, 
    			WPARAM wParam, LPARAM lParam)
    {
    	switch(msg)
    	{
    
    	case WM_ACTIVATE :
    		{
    			active = HIWORD(wParam) ? false : true;
    
    			return 0;
    		}
    
    	case WM_CLOSE :
    		{
    			PostQuitMessage(0);
    			return 0;
    		}
    
    	case WM_SIZE :
    		{
    			width = LOWORD(lParam);
    			height = HIWORD(lParam);
    			
    			if (resize)
    				resize(LOWORD(lParam), HIWORD(lParam));
    
    			return 0;
    		}
    		
        case WM_KEYDOWN :
    		if (wParam == VK_RIGHT)
               {xmov += 0.1f;}
            if (wParam == VK_LEFT)
               {xmov -= 0.1f;}
            if (wParam == VK_UP)
               {ymov += 0.1f;}
            if (wParam == VK_DOWN)
               {ymov -= 0.1f;}
            if (wParam == VK_SPACE)
               {anrot += 180.0f;
                xrot += 45.0f;
                yrot += 45.0f;}
            }
    
    	return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    I don't think you need anymore of the code. If you need anymore, please tell me.

    I know this seems stupid to belong in Game Programming... >.<

    Thanks in advance!

  2. #2
    Registered User
    Join Date
    Nov 2005
    Posts
    545
    Perhaps the code that rotates it should just be reversed. it would make sense, sometimes things that you don't expect happen, maybe in your code you have got your directions mixed up.

  3. #3
    Registered User
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    Aug 2003
    Posts
    1,197
    ok try change glRotatef(anrot, xrot, yrot, 1.0f); to glRotatef(anrot, 0.0, 0.0, 1.0f); and change
    Code:
    if (wParam == VK_SPACE)
               {anrot += 180.0f;
                xrot += 45.0f;
                yrot += 45.0f;}
            }
    to

    Code:
    if (wParam == VK_SPACE)
               {
                    anrot += 90.0f;
               }
            }

  4. #4
    Super Moderator VirtualAce's Avatar
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    9,586
    Tetris uses 90 degree rotations as Shakti has pointed out. And unless this is 3D tetris, you are going about this the wrong way.

    It appears you are doing a 2D tetris. If so you should be using a different method to present the graphics.

    1. Tetris is a grid.
    2. Numbers on the grid represent colors or empty space.
    3. Blocks are composed of numbers representing colors and are built via offset tables.
    4. Your renderer simply scans an array from TOP to BOTTOM and draws blocks.
    5. Your board is setup so that pieces occupy the correct blocks to make them 'appear' as pieces
    6. TOP changes as the board changes.
    Last edited by VirtualAce; 01-15-2007 at 01:56 AM.

  5. #5
    Registered User Kenoriga's Avatar
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    Location
    Singapore
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    Whoop. Thanks for the help everyone! Shakti's solution worked!

    How come it doesn't work if I add 0.1f to xrot and yrot?

    Thanks again woohoo. I got stuck like almost one month... I feel so stupid now.

  6. #6
    Registered User
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    Aug 2003
    Posts
    1,197
    because you rotate around the wrong axis. xrot, yrot and zrot determines the vector around which you rotate the object. the z-axis goes in and out of the screen and is the only one you want to rotate around if you do 2D games. I suggest reading up on the function glRotatef to get a better understanding of how it works.

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