Recent content by marmakoide

  1. M

    GP2X Fixed Vs. Float

    Ok. I see two reasons to have floating point faster than fixed point : 1) Your test function is optimised very cleverly by the compiler. If you test is something like : a = 3.141592 b = 6.666 c = a * b The compiler is able to precompute 3.141592 * 6.666 for the floating point version of this...
  2. M

    GP2X Fixed Vs. Float

    The cheese as nothing to do with confusion, that's a French frog that said that to you :P ! Indeed, yes, you right, at least recent GCC versions (4.x.x) are able to generate optimized code for the operations implying float constants.
  3. M

    GP2X Fixed Vs. Float

    Well, I think you don't use correctly fixed point. Doing software floating point operation is MUCH slower. Just compare the assembler code needed by an addition, a multiplication, or a square root ! And the difference is even greater when the fixed point usage is implicit like in the Bresenham...
  4. M

    Down With The Blitter

    Yeeeeeeaaaaaah, got it ! I was listening Born to be wild, I was reading the SDL code source, scratcing my head, and... voila ! Hardware accelerated rectangle blitting ! Now I'am yelling in my room, jumping around :D The point I missed : the blitter understand only PHYSICAL adress, not the mmu...
  5. M

    Down With The Blitter

    Excuse me, I'am not sure to understand what you mean. You said that in my init phase, I must set the register BLITTER_REG_RUN to 0 ? Or do I must perform a full dummy blit in my init phase ?
  6. M

    Down With The Blitter

    Hi all I'm trying to use the blitter to fill rectangle with a single color. By reading the harware optimised SDL, I do this way : 1) Magic to enable the blitter operations gp2x_mem_fd = open("/dev/mem", O_RDWR); blitter_regs_32 = (unsigned int*)mmap(0, 256, 3, MAP_SHARED, gp2x_mem_fd...
  7. M

    GP2X Optimizing A Routine For Speed

    To have fast rectangles, a call to the blitter is a must, it's faster than the fastest pixels-by-pixels algorithm. See the GP2X wiki and the harware optimised SDL to do that.
  8. M

    GP2X Planning My Software 3d Renderer

    Yes, raycasting is perfect for a 3d illusion (only 4 degrees of freedom, 5 with some works), not for true 3d (but it's possible, check the Ken Silverman Voxlap engine). But why fighting for true 3d when the illusion is good enought ? For a fast paced fps, I think it's okay.
  9. M

    GP2X Planning My Software 3d Renderer

    Well, before focusing on assembler, MMu hack and the blitter, focus on the algorithm. When using a vector instead of a linked list (for random index insertion as instance), even the most optimised vector on an overclocked CPU is slow. 'O(1) versus O(n)' or thing like this before anything. For a...
  10. M

    System Calls Reference Doc

    :D Got it ! I'am not that ignorant in computer science, but a real noob for the low level stuffs. Here it is my self answer, so that other newbies like me will find their way in less time than me. What I was searching is : the interrupts code used to call a given function of the Linux kernel...
  11. M

    System Calls Reference Doc

    Hi everybody I made for my personal use a little C library, in the spirit of the Rlyeh lib : no C standard lib, simple memory management withou mallocs. But I still need to speak a little bit with Linux. Currently, I ripped an assembler source code from Dzzz tutorials. Here it is the beast...
  12. M

    GP2X Jabber's Log-fire

    Finite state machines could enougth to control such LCD games, don't you think so ? You will a have a generic emulator of LCD games. An LCD game is a finite state machine with a picture file. My 2 cents.
  13. M

    Interrupt To Check Keys And Joystick

    Actually, I do like Squidge said : after each vblank, I grab the 0x1184 register. But I was quite afraid to miss buttons events, leading to poor game controls. Anyway, you true, 50 hz is not so bad sampling frequency, Keep It Simple Stupid... So I will keep this way.
  14. M

    Interrupt To Check Keys And Joystick

    Ok, after some further readings, it seems that catching the interrupts like in the good old DOS time (int 9 to be precise) is not possible under good OSs like Linux. So my question is now : * In the "without SDL" case, how do you handle the keyboard and joysticks event ?
  15. M

    Interrupt To Check Keys And Joystick

    Hi all ! I'am just beginning to get into the GP2X development, learning by making tiny demos. I want to bypass the SDL, to get a full freedom and speed (and also pain :P). My actual main problem is to get the events from the keys and the joystick. what I do now Direct read of the keys...
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