GRRLib Forum / How to copy what's on the screen to use it later?

Crayon · 2008-07-04 07:39:59

Hi, if in my game I want to copy what's on the screen to use it later. I need to copy the buffer xfb[fb]?

Is there a function to do that, I know memcpy would work, but is there a GX function?

RedShade · 2008-07-07 19:13:02

The xfb is sort of a lower resolution image, and is on the CPU's side. To copy parts of an image, you would use the following functions on GX:

Code:

GX_SetTexCopySrc(u16 left,u16 top,u16 wd,u16 ht);//This sets the location on the efb you want to copy from
GX_SetTexCopyDst(u16 wd,u16 ht,u32 fmt,u8 mipmap);//This is what kind of texture you want to copy from 
//format is close to the texture initializer if you know what that is.
// To make it the same format as what you are using in GRRLIB, you would set this to (width,height, GX_TF_RGBA8,GX_FALSE)

//Next, make a buffer to hold the texture:
u8 * newTexture = memalign(32, GX_GetTexBufferSize(width,height,GX_TF_RGBA8,GX_FALSE,1));

GX_CopyTex(newTexture, boolClear);//do you want to clear the buffer after copying the image portion?

Last edited by RedShade (2008-07-07 19:14:04)

Crayon · 2008-07-08 06:16:44

I tried this function:

Code:

/**
 * Make a snapshot of the sreen in a texture.
 * @return A texture representing the screen.
 */
u8 *GRRLIB_Screen2Texture() {
    void *my_texture;

    GX_SetTexCopySrc(0, 0, 640, 480);
    GX_SetTexCopyDst(640, 480, GX_TF_RGBA8, GX_FALSE);
    my_texture = memalign(32, 640 * 480 * 4); // GX_GetTexBufferSize(640, 480, GX_TF_RGBA8, GX_FALSE, 1)
    GX_CopyTex(my_texture, GX_FALSE);
    return my_texture;
}

It's almost working, the only problem I have is when I put back the texture on screen. There is weird pixels on the top of the screen. They appear while drawing on top of the texture (when I move the cursor or when the button is changing state).

This is my code to copy the screen to a texture:

Code:

u8 *CopiedImg;
CopiedImg = GRRLIB_Screen2Texture();

This my code to put it back on the screen:

Code:

GRRLIB_DrawImg(0, 0, 640, 480, CopiedImg, 0, 1, 1, 255);

The libOGC Documentation is not accurate on some function arguments:
http://libogc.devkitpro.org/

For example:

Code:

/*! 
 * \fn void GX_SetTexCopyDst(u16 wd,u16 ht,u32 fmt,u8 mipmap)
 * \brief Copies the embedded framebuffer(XFB) to the texture image buffer <b><i>dest</i></b> in main memory. This is useful
 *        when creating textures using the Graphics Processor(CP).
 *        If the <b><i>clear</i></b> flag is set to GX_TRUE, the EFB will be cleared to the current color(see GX_SetCopyClear()) 
 *        during the copy operation.
 *
 * \param[in] wd pointer to the image buffer in main memory. <b><i>dest</i></b> should be 32B aligned.
 * \param[in] ht flag that indicates framebuffer should be cleared if GX_TRUE.
 * \param[in] fmt \ref texfmt
 * \param[in] mipmap 
 *
 * \return none
 */

I'm so close to make this work, if you have an hint I would appreciate it a lot.

Thanks!

Crayon · 2008-07-08 16:31:49

This is what I get at the top of my screen:

I cut the rest of the screenshot because all the rest is ok???

RedShade · 2008-07-08 23:28:21

Something is writing over your the texture, either from an incomplete draw to EFB, or between the copy of the texture and the drawing back onto the EFB :-/...

What settings are confusing? It's similar to :
GX_InitTexObj (GXTexObj *obj, void *img_ptr, u16 wd, u16 ht, u8 fmt, u8 wrap_s, u8 wrap_t, u8 mipmap)

except you don't set wrapping or texobj

have you tried it on smaller code segments? *The kind of thing that can be pasted here to look over, or on pastie or something to try out.

Last edited by RedShade (2008-07-08 23:29:14)

Crayon · 2008-07-09 00:16:34

Right now I'm not at home, so this is the information that I can provide. I will do some test tonight.

I'm working in C++ project, so CopiedImg is private attribute declare as u8 *. These are all the places where CopiedImg is being used:

This for my HOME page (when the HOME button is pressed). I only want draw the game screen once and to add an effect on it. CopiedImg will be used has a background image, buttons and other stuff will be draw over it:

Code:

    if(CopiedImg == NULL)
    {
        GameScreen(); // Draw the game screen
        GRRLIB_Rectangle(0, 0, 640, 480, 0xCC000000, 1); // Make the screen look disable
        CopiedImg = GRRLIB_Screen2Texture();
    }
    else
    {    // Put the copied texture on screen
        GRRLIB_DrawImg(0, 0, 640, 480, CopiedImg, 0, 1, 1, 255);
    }

    // Buttons are drawn on screen
    ExitButton[0].Paint();
    ExitButton[1].Paint();
    ExitButton[2].Paint();

When I change screen (going back in the game) this code is called, I don't know if it's proper way to free a texture:

Code:

    if(CopiedImg)
    {
        free(CopiedImg);
        CopiedImg = NULL;
    }

In my constructor I have:

Code:

    CopiedImg = NULL;

In my destructor I have:

Code:

    if(CopiedImg)
        free(CopiedImg);

Crayon · 2008-07-09 06:44:56

OK just a small update, I was able to make it work correctly by loading a 640x480 texture to CopiedImg before using it.

So my code in the constructor is now:

Code:

    CopiedImg = GRRLIB_LoadTexture(splash);

splash is the image I'm using for my intro screen. I don't know what is going on in GRRLIB_LoadTexture, but it is now initializing correctly.

I still want to understand the problem, so if someone has a idea on how to solve it, well post it here...

RedShade · 2008-07-09 19:19:58

Don't think that does anything but shift the memory around a little. You are still having a pointer that is doing:
CopiedImage -> 0;
CopiedImage -> points to splash
CopiedImage -> points to screen capture
so the logic goes:
u32 ptr = 0;
//ptr = 1; //uncommenting this line changes the result?
ptr = 2;

I believe free(ptr) is the correct way to free memalign-ed memory

I don't know if GX_DrawDone() would help in the copying of the texture or not :-/

Crayon · 2008-11-22 20:52:07

I think that the DCFlushRange line fixed the problem, I saw that in the snes9x-gx code.
So the function should look like this:

Code:

u8 *GRRLIB_Screen2Texture() {
    void *my_texture;

    GX_SetTexCopySrc(0, 0, 640, 480);
    GX_SetTexCopyDst(640, 480, GX_TF_RGBA8, GX_FALSE);
    my_texture = memalign(32, 640 * 480 * 4); // GX_GetTexBufferSize(640, 480, GX_TF_RGBA8, GX_FALSE, 1)
    GX_CopyTex(my_texture, GX_FALSE);
    GX_PixModeSync();
    DCFlushRange(my_texture, 640 * 480 * 4);
    return my_texture;
}

sammystag · 2008-12-03 16:35:32

Hi,

This function looks like just what I need, but there seems to be a bug with it (or else with GRRLIB_DrawImg) or I am misunderstanding something.

I am using this function to copy the screen buffer before rendering it so that I can re-use it - looking at the tic-tac-toe source, this seems to be correct.

If I use this function in a loop, my graphics fall off the bottom of the screen so it seems that the screen image is being rendered slightly lower down when re-draw it.

The following program demonstrates the problem. It draws a rectangle and then when you press "A" it goes into a loop which should just keep redrawing the screen as is, but in fact the rectangle falls off the bottom.

Code:

#include <wiiuse/wpad.h>
#include "GRRLIB/GRRLIB.h"

Mtx GXmodelView2D;


u8 *GRRLIB_Screen2Texture() {
    void *my_texture;

    GX_SetTexCopySrc(0, 0, 640, 480);
    GX_SetTexCopyDst(640, 480, GX_TF_RGBA8, GX_FALSE);
    my_texture = memalign(32, 640 * 480 * 4); // GX_GetTexBufferSize(640, 480, GX_TF_RGBA8, GX_FALSE, 1)
    GX_CopyTex(my_texture, GX_FALSE);
    GX_PixModeSync();
    DCFlushRange(my_texture, 640 * 480 * 4);
    return my_texture;
}


int main(){
    VIDEO_Init();
    WPAD_Init();

    GRRLIB_InitVideo();
    GRRLIB_Start();

    GRRLIB_FillScreen(0xFF000000);
    GRRLIB_Rectangle(100,100,200,100,0xFFFFFFFF,1);
    
    // copy the soon to be rendered screen to an image
    u8 *copiedImg = GRRLIB_Screen2Texture();
    
    GRRLIB_Render();

    // just wait for A to be pressed
    bool aPressed = false;
    while(!aPressed){
        WPAD_ScanPads();
        u32 wpaddown = WPAD_ButtonsDown(0);
        aPressed = (wpaddown & WPAD_BUTTON_A);

    }

    // loop copying and redrawing until A pressed again
    aPressed = false;
    while(!aPressed){
    
        // draw the previously copied screen image
        GRRLIB_DrawImg(0, 0, 640, 480, copiedImg, 0, 1, 1, 255);
        
        // free the memory
        free(copiedImg);
        
        // copy the updated screen
        copiedImg = GRRLIB_Screen2Texture();
        
        //render the screen
        GRRLIB_Render();

        // exit when we press A
        WPAD_ScanPads();
        u32 wpaddown = WPAD_ButtonsDown(0);
        aPressed = (wpaddown & WPAD_BUTTON_A);

    }
    
    free(copiedImg);
    return 0;
}

Thanks,

SammyStag

Crayon · 2008-12-03 20:22:44

Yes your right, since I was not using it in a loop I never felt like finding a solution for that issue. Anyway I suck with GX functions. Hopefully someone will find a solution.

Meanwhile, you could try to use this:

Code:

GRRLIB_DrawImg(0, -1, 640, 479, copiedImg, 0, 1, 1, 255);

Right now I could not test it (not at home).

sammystag · 2008-12-04 16:26:07

Thanks for the reply, unfortunately this doesn't seem to fix it.

I tried a few other values and strange things happen. For example

Code:

GRRLIB_DrawImg(0, -20, 640, 460, copiedImg, 0, 1, 1, 255);

has the image stretch out to the top and bottom of the screen and then horizontally as it becomes ghost like. I wasn't sure if the 4th argument should remain at 480, but that didn't seem to make any difference.

NoNameNo · 2008-12-05 09:28:29

as i already said a lot of times, be sure to use the latest libogc !!! old version produce "VOODOO gx effects". catch the svn version and tell us if it resolv your stuff.

sammystag · 2008-12-07 13:51:56

I've tried this again with the new libogc 1.7.0 release and am still getting the same results.

#1 2008-07-04 07:39:59

How to copy what's on the screen to use it later?

#2 2008-07-07 19:13:02

Re: How to copy what's on the screen to use it later?

Code:

#3 2008-07-08 06:16:44

Re: How to copy what's on the screen to use it later?

Code:

Code:

Code:

Code:

#4 2008-07-08 16:31:49

Re: How to copy what's on the screen to use it later?

#5 2008-07-08 23:28:21

Re: How to copy what's on the screen to use it later?

#6 2008-07-09 00:16:34

Re: How to copy what's on the screen to use it later?

Code:

Code:

Code:

Code:

#7 2008-07-09 06:44:56

Re: How to copy what's on the screen to use it later?

Code:

#8 2008-07-09 19:19:58

Re: How to copy what's on the screen to use it later?

#9 2008-11-22 20:52:07

Re: How to copy what's on the screen to use it later?

Code:

#10 2008-12-03 16:35:32

Re: How to copy what's on the screen to use it later?

Code:

#11 2008-12-03 20:22:44

Re: How to copy what's on the screen to use it later?

Code:

#12 2008-12-04 16:26:07

Re: How to copy what's on the screen to use it later?

Code:

#13 2008-12-05 09:28:29

Re: How to copy what's on the screen to use it later?

#14 2008-12-07 13:51:56

Re: How to copy what's on the screen to use it later?

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