Screen flicker

[grakoczy]

Hi,

Is there any way to avoid screen flickering when I cycle draw lines / erase screen? Both operations take a while and it's visible as flicker.
I've never really programmed 8 bit machines back in the 80's so I don't know the tricks.
There is are no screen tearing so I think it's not a vsync issue.
Here is how it looks so far.

3d.cube.RP6502.mp4

[rumbledethumps]

Double buffering.

[grakoczy]

Is this possible on RP6502?

[WojciechGw]

320x240 yes
640x480 no (due to XRAM size)

proof below
(blinking pixels in upper corners indicate buffer switching)

3dcube_doublebuffering+.mp4

[grakoczy]

Hi,
Looks great. How did you do that?

[WojciechGw]

First of all thank You very much for 3d transformation functions :)

Magic is done by drawing things to two different address spaces in XRAM and switching between them

0. clear inactive buffer
1. draw things to inactive buffer
2. switch to inactive buffer
3. goto 0.

I've made some changes to tonyvr's bitmap_graphics library and Your main.c
so all functions are double buffering friendly now

in bitmap_graphics_db.c

void switch_buffer(uint16_t buffer_data_address)
{
    xram0_struct_set(canvas_struct, vga_mode3_config_t, xram_data_ptr, buffer_data_address);
}

main.c in main loop

[...]
     buffers[0] = 0x0000;
     buffers[1] = 0x2580;
[...]
      // draw on inactive buffer
      erase_buffer(buffers[!active_buffer]);
      draw_cube(angleX, angleY, angleZ, WHITE, mode, buffers[!active_buffer]);
      switch_buffer(buffers[!active_buffer]);
      active_buffer = !active_buffer;
[...]

in main CMakeList.txt

add_executable(cube)
rp6502_executable(cube)
target_sources(cube PRIVATE
    src/colors.c
    src/bitmap_graphics_db.c
    src/main.c
)

all changed files in .zip
3dcube_DoubleBuffering.zip

Bon apetite !

[grakoczy]

Thanks!
Now it works great :)

--
Grzegorz

[WojciechGw]

my pleasure :)

double buffering capable resolutions

canvas_w	canvas_h	bpp	pixels	buffer size
640	360	1	230400	28800
320	240	2	76800	19200
320	240	1	76800	9600
320	180	4	57600	28800
320	180	2	57600	14400
320	180	1	57600	7200
240	124	8	29760	29760
240	124	4	29760	14880
240	124	2	29760	7440
240	124	1	29760	3720

sorry, just noticed garbage in main.c
You can delete

int16_t cube_vertices_c[8][3] = {
    {-4096, -4096, -4096}, {4096, -4096, -4096}, {4096, 4096, -4096}, {-4096, 4096, -4096},  // Back face
    {-4096, -4096,  4096}, {4096, -4096,  4096}, {4096, 4096,  4096}, {-4096, 4096,  4096}   // Front face
};

it was for testing purposes only

[WojciechGw]

continuing the topic,
take a look at this

3dcube.zip

source[3dcube].zip

[grakoczy]

Nice!
Merged to the repository: https://github.com/grakoczy/RP6502-3D-cube-llvm-mos

[vruumllc]

Great demo! I love it.