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21

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on March 10, 2025, 04:24:00 PM »

I found out the following by myself : 

a) if i have declared my points as integer values like "mydata dq 100" or whatever, I should not load them like "movsd xmm0, qword [mydata]" but with  "cvtsi2sd xmm0, qword [mydata]"

b) if I really work with my data as integer, they will get after a few rotation-calculations very fast unexact by the truncation/rounding.  After a 360 degree-rotation in 360 steps I will have no more a cube, but some totally other formation. ;-)    => Will have to do this with floating-point (also the storing of the coordinates)

22

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on March 06, 2025, 10:33:37 PM »

So, I am trying my luck with sdl2.  A llittle cube defined by 8 points and the lines between it...  Moving works, but the rotating stuff isn't working, it calculates wrong values.
Because of the sinus and cosinus, I had to go with sse2, but something seems to be wrong.

I have my data like this :

section .data
xs    dq 0,0,0,0,0,0,0,0,0,0,0,0
ys  dq 0,0,0,0,0,0,0,0,0,0,0,0
points resq 24
tempx dq 0
tempy dq 0
tempz dq 0



                              ; reminder 960 x 720 window, haelfte 480 / 360
point dq    -100, -100, 300,
dq         100, -100, 300,
dq         -100, 100, 300,
dq         100, 100, 300,
dq         -100, -100, 500,
dq         100, -100, 500,
dq         -100, 100, 500,
dq         100, 100, 500   


yaussen dq 700                                 ; war erst 900 und 400
yscreen dq 100                                 ; reminder 960 x 720 window, haelfte 480 / 360

cos1 dq 0.9998477                     ; 0.9998477*x - 0.0174524*z;
sin1 dq 0.0174524

...the point-table will be written to the points-array.  Works, shifting to left, right, up, down, and in the depth worksall, but than comes a try of rotation ...

roty1:
   push rcx
   push r15
   mov rcx, 0
   nochmal8:                           ; tempx:= 0.9998477*x - 0.0174524*z
   movsd xmm0, qword [points+rcx*8]         ; load  x coordinate in xmm0
   movsd xmm1, qword [cos1]               ; load cos 1 from table in xmm1
   mulsd xmm0, xmm1                     ; multiply xmm0 and xmm1, store in xmm0
   movsd xmm2, qword [points+rcx*8+16]        ; load  z coordinate in xmm2
   movsd xmm3, qword [sin1]               ; load sin 1 from table in xmm3
   mulsd xmm2, xmm3                     ; multiply xmm2 and xmm3, store in xmm2
   subsd xmm0, xmm2                     ; subtract xmm2 from xmm0, store in xmm0
   mov r15, 0
   cvtsd2si r15, xmm0                     ; convert xmm0 to integer and store in r15
   mov qword [tempx], r15                  ; store tempx

                                    ; tempz:= 0.0174524*x + 0.9998477*z
   movsd xmm0, qword [points+rcx*8]         ; load  x coordinate in xmm0
   movsd xmm1, qword [sin1]               ; load sin 1 from table
   mulsd xmm0, xmm1                     ; multiply and store in xmm0
   movsd xmm2, qword [points+rcx*8+16]        ; load  z coordinate
   movsd xmm3, qword [cos1]               ; load cos 1 from table
   mulsd xmm2, xmm3                     ; multiply and store in xmm2
   addsd xmm0, xmm2                     ; add xmm0 and xmm2, store in xmm0
   mov r15, 0
   cvtsd2si r15, xmm0                     ; convet xmm0 to integer and store in r15
   mov qword [tempz], r15                  ; store tempz
   
   mov r15, 0
   mov   r15, [tempx]
   mov [points+rcx*8], r15                  ; write the new x coordinate to table
   mov r15, 0
   mov   r15, [tempz]
   mov [points+rcx*8+16], r15               ; same for z coordinate
   

   inc rcx
   inc rcx
   inc rcx
   cmp rcx, 24                           ; eight point in the cube, each with three coordinates...
   jne nochmal8

   pop r15
   pop rcx
ret

Rotation by y.
If I let calculate the stuff in Excel, I have good valuaes, but the conversion in Assembly-Code does not get me the right values.

Does anybody see obvious failures in the code?

Thanks in advance, Andy from the nightly sleeping Germany

23

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on February 25, 2025, 05:10:06 PM »

I will test it "as last option" with breakpoints, but I think, it might be easier for me to comment out the sdl and graphic stuff, so I have only the calculating part working.  I just want to control my calculated coordinates by hand.  This should work.

(If i get it to work I surely will be here in some days to ask you for faster and better calculating algorithms. ;-) )

 

24

Other Discussion / Re: framebuffer problem

« Last post by fredericopissarra on February 23, 2025, 06:44:20 PM »

Ah, now i remember : sdl2 is using multithreading so Debugging (at least with my knowledge and radare2) is not working. Seems, that i have to create a  few macros for Output of Registers, while doing calculating stuff to find the Point of Errors.

Here works perfectly:

Code: [Select]

/* test.c */
#include <stdio.h>
#include <pthread.h>

unsigned int count = -1;

static void *thread( void *p )
{
  while ( count-- );

  return NULL;
}

int main( void )
{
  pthread_t tid;

  pthread_create( &tid, NULL, thread, NULL );
  getchar();
  pthread_join( tid, NULL );

  return 0;
}


Code: [Select]

$ cc -g -pthread -o test test.c
$ gdb test
GNU gdb (Ubuntu 15.0.50.20240403-0ubuntu1) 15.0.50.20240403-git
...
Reading symbols from test...
(gdb) list
1 #include <stdio.h>
2 #include <pthread.h>
3
4 unsigned int count = -1;
5
6 void *thread( void *p )
7 {
8   while ( count-- );
9
10   return NULL;
(gdb) b 8
Breakpoint 1 at 0x11b5: file test.c, line 8.
(gdb) r
Starting program: /mnt/vol2/work/tmp/test
Downloading separate debug info for system-supplied DSO at 0x7ffff7fc3000
[Thread debugging using libthread_db enabled]                                                                                               
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff7bff6c0 (LWP 67336)]
[Switching to Thread 0x7ffff7bff6c0 (LWP 67336)]

Thread 2 "test" hit Breakpoint 1, thread (p=0x0) at test.c:8
8   while ( count-- );
(gdb) p count
$1 = 4294967295
(gdb) quit
A debugging session is active.

Inferior 1 [process 67332] will be killed.

Quit anyway? (y or n) y
$

25

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on February 22, 2025, 07:54:31 PM »

Ah, now i remember : sdl2 is using multithreading so Debugging (at least with my knowledge and radare2) is not working. Seems, that i have to create a  few macros for Output of Registers, while doing calculating stuff to find the Point of Errors.

26

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on February 20, 2025, 07:18:35 PM »

OK...  Thanks you Frederico!  I think, I will do my stuff at sdl2, It is already installed in my system.

27

Other Discussion / Re: framebuffer problem

« Last post by fredericopissarra on February 19, 2025, 11:10:33 PM »

Do you know If one of both framebuffer / sdl is faster as the other?

fbdev don't offer any acceleration support, not even in 2D like Bit Block Transfers (Bitblt)... SDL (2 and 3) does.

28

Other Discussion / Re: framebuffer problem

« Last post by andyz74 on February 19, 2025, 05:53:36 PM »

OK. I will check the Video drivers, If I manage to find Out how. 😂

Do you know If one of both framebuffer / sdl is faster as the other?

29

Other Discussion / Re: framebuffer problem

« Last post by fredericopissarra on February 19, 2025, 12:18:30 PM »

You have to make sure that your video drivers support /dev/fb? and make sure it is enabled in kernel configs, AND if it is accessible to your user...

It is better to use SDL2 (or 3, it is available now!).

30

Other Discussion / framebuffer problem

« Last post by andyz74 on February 18, 2025, 05:51:12 PM »

Hello and good evening!

I've done a little experimenting in doing easy graphic-stuff by writing direct to framebuffer /dev/fb0  (Debian Linux 64bit here)
Mainly in Free Pascal, before testing in Assembly.
While getting lots of garbage as output I also tested code, where I think it HAS to be good and HAS to work, I also got garbage.
( https://github.com/xmdi/SCHIZONE/tree/main/ex/ex020_framebuffer )   
If I test it on my Laptop (also Debian), it works, but not here on my beloved Desktopcomputer.

Now to my questions :
1) Is there anything I have to configure on my framebuffer in my Linux, and
2) Is it worth the time, or should I better invest time in SDL2 for doing graphics stuff?

Greetz, Andy