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Thread: glDrawPixels() help

  1. #1
    Newbie Newbie
    Join Date
    Oct 2012
    Posts
    1

    glDrawPixels() help

    So, I am trying to use glDrawPixels() to draw points on the screen but can't get it to work properly. Right now it draws the points I want, but then repeats the points in the same position on the y-axis but translated over a few pixels on the x-axis repeatedly.


    I am creating a pixel buffer like so:

    Code :
    struct RGBType {	
    	float r;	
    	float g;	
    	float b;
    };
     
    RGBType *pixel_buffer = new RGBType[800 * 1200];

    Then filling in the rgb components I want to show up on the screen
    Code :
    pixel_buffer[800*y + x].r=0.5;		
    pixel_buffer[800*y + x].g=0.5;		
    pixel_buffer[800*y + x].b=0.5;

    and then calling drawpixels and swapping the buffers
    Code :
    glDrawPixels(window_width, window_height, GL_RGB, GL_FLOAT, pixel_buffer);
    glutSwapBuffers();
    delete[] pixel_buffer;

    All my other code is simply setting up a window with glut.

  2. #2
    Super Moderator OpenGL Guru
    Join Date
    Feb 2000
    Location
    Montreal, Canada
    Posts
    4,264
    Maybe you are using some other function that is causing the raster position to change. Call glRasterPos before calling glDrawPixels.
    ------------------------------
    Sig: http://glhlib.sourceforge.net
    an open source GLU replacement library. Much more modern than GLU.
    float matrix[16], inverse_matrix[16];
    glhLoadIdentityf2(matrix);
    glhTranslatef2(matrix, 0.0, 0.0, 5.0);
    glhRotateAboutXf2(matrix, angleInRadians);
    glhScalef2(matrix, 1.0, 1.0, -1.0);
    glhQuickInvertMatrixf2(matrix, inverse_matrix);
    glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
    glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);

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