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Thread: GLDirectOpengl for 2D graphics

  1. #1

    GLDirectOpengl for 2D graphics

    I have very fast 2D graphics working very nicely using the GLDirectOpengl, with anti-aliasing. I am drawing 800 000 pixels, and am getting very high frame rates, over 50 FPS.

    procedure TForm1.GLDirectOpenGL1Render(Sender: TObject;
    var rci: TRenderContextInfo);
    var
    i,j, x, y : Integer;
    glc : TGLCanvas;
    r : TRect;
    color : TColor;

    begin
    glc:=TGLCanvas.Create(glsceneviewer1.width,glscene viewer1.height);


    { for x:=0 to 1000 do
    for y:=0 to 800 do
    begin
    glc.PenColor:=clyellow;
    glc.PlotPixel(x,y);
    end;}

    glc.Free;
    end;


    I have a few questions:

    1. How would one do 2d Graphics using OpenGL and not glsscene? I like glscene, but am looking for something with minimal overhead.

    2. With the code above, and without using PlotPixel, is there any way to bitblt a bmp to the screen? Or do I need to create a polygon and put a texture onto it?

  2. #2
    A whole picture like bmp drawn as texture with quad is definitely 10000 times faster than plotting it in pixels.

  3. #3
    Quote Originally Posted by Ray
    How would one do 2d Graphics using OpenGL and not glsscene? I like glscene, but am looking for something with minimal overhead.
    ZenGL
    Quote Originally Posted by Ray
    Or do I need to create a polygon and put a texture onto it?
    Yes, this is the fastest way to draw image on the screen, but with any 2d engine you will not have to worry about this.

  4. #4
    Is there an example for doing the following with GLDirectOpengL:

    1. Draw some lines. - Done
    2. Draw some test. - Done
    3. Draw a bitmap or dib on the GLDirectOpengl surface.

    For the last one, I do not see any bitmap type functions in the unit for GLDirectOpengl. What would the code be to draw a simple bitmap? Or do I need to use all the 3D stuff.

  5. #5
    Ok, did it like this:

    //put a glplane onto the viewing area (orientate it so that it looks 2d) and assign a bitmap to it. Is there a faster way?

    procedure TForm1.SpeedButton2Click(Sender: TObject);
    var
    rbitmap : tbitmap;
    begin
    rbitmap:=tbitmap.Create;
    rbitmap.SetSize(200,200);
    // glplane1.Material.Texture.Image.AssignToBitmap(rbi tmap);
    glplane1.Material.Texture.Image.Assign(rbitmap);

    end;

  6. #6
    Okay I've been experimenting with this:

    procedure TForm1.GLDirectOpenGL1Render(Sender: TObject;
    var rci: TRenderContextInfo);
    var
    i,j, x, y : Integer;
    color : TColor;
    begin
    glc:=TGLCanvas.Create(glsceneviewer1.width,glscene viewer1.height);

    //method 1
    with glc do
    begin
    for x:=0 to 499 do
    for y:=0 to 499 do
    begin
    PenColor:=rgb(random(255),random(255),random(255)) ;
    plotpixel(x,y);
    end;
    end;



    glc.Free;

    //method 2
    for x:=0 to 499 do
    for y:=0 to 499 do
    begin
    testdib.Pixels[x,y]:=rgb(random(255),random(255),random(255));
    end;
    glplane1.Material.Texture.Image.Assign(testdib);
    end;

    I am drawing 2 blocks using different methods. Method 1 is to use the glcanvas. Method 2 is to use a glplane, draw the pixels on the dib and then copy them to the glplane's material. Writing to the DIB itself is very very fast and doesn't slow things sown much at all. The problem is trying to get the dib onto the plane.

    Method 1 by itself I get 50FPS.

    Method 2 by itself I get 15 FPS

    Method 2 without assigning the testdib to the plane's material, I get 60FPS.

    So I conclude that Method 2 has a bottleneck of glplane1.Material.Texture.Image.Assign(testdib);

    My questions are:

    1. Is there any way to get the tdib into the glplane faster than using assign?

    2. OR is there a completely different (and much faster) way of putting pixels on the screen than using the 2 methods above?

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