Rolling Shutter Effect Explained Even Cheaper (than Matt Parker)

[@rt]

Hi Guys
This is a video reply to a video reply by standupmaths, to a video by SmarterEveryDay.
I hope you enjoy

[@rt]

I cleaned up the software a little, mainly because I forgot the all important comparison propeller without the effect.
This is roughly 120x240 with a palette of 256 colours.

[firewalker]

No code? How do you expect us to criticize and correct you? 

Alexander.

[@rt]

It was definitely about making an animation rather than writing a program, but go for your life

First thing I’d do is roll the circle drawing into loops, then create an array of the four rotating points,
and roll the propeller blades into a loop as well.

Code: [Select]


void transferToScreen() {
   
    unsigned int  lrow;
    unsigned int  lcol;
    unsigned int  lpixelvalue;
   
    for (lrow = smlsizey-1; lrow > 0; lrow--) { // delete previous frame from bitmap
    for (lcol = 0; lcol < FDATA_HEIGHT; lcol++) {
    lpixelvalue = 0;firedata[lcol][lrow] = 0x00;
    imgdata[bmpindex] = (lpixelvalue >> 16) & 0xFF;
    imgdata[bmpindex+1] = (lpixelvalue >> 8) & 0xFF;
    imgdata[bmpindex+2] = lpixelvalue & 0xFF;
    bmpindex+=3;
    }}
   
    // do propeller rotation
    int increment = 6
    rotation = rotation + increment;
    if (rotation > (360-increment)) {rotation = 0;}
   
    ox = 75; oy = 80; // propeller blade a
    x = 75; y = 20; // 7
    pixelrotation();
    drawline(ox,oy,x,y);
    lcol = xnew; lrow = ynew;
    cx = xnew; cy = ynew; radius=5; drawcircle();
    cx = xnew; cy = ynew; radius=4; drawcircle();
    cx = xnew; cy = ynew; radius=3; drawcircle();
    cx = xnew; cy = ynew; radius=2; drawcircle();
    cx = xnew; cy = ynew; radius=1; drawcircle();
    firedata[lcol][lrow] = 0x2F; // prop edge a

    ox = 75; oy = 80; // propeller blade b
    x = 75; y = 140;
    pixelrotation();
    drawline(ox,oy,x,y);
    lcol = xnew; lrow = ynew;
    cx = xnew; cy = ynew; radius=5; drawcircle();
    cx = xnew; cy = ynew; radius=4; drawcircle();
    cx = xnew; cy = ynew; radius=3; drawcircle();
    cx = xnew; cy = ynew; radius=2; drawcircle();
    cx = xnew; cy = ynew; radius=1; drawcircle();
    firedata[lcol][lrow] = 0x3F; // prop edge b
   
    ox = 75; oy = 80; // propeller blade c
    x = 135; y = 80;
    pixelrotation();
    drawline(ox,oy,x,y);
    lcol = xnew; lrow = ynew;
    cx = xnew; cy = ynew; radius=5; drawcircle();
    cx = xnew; cy = ynew; radius=4; drawcircle();
    cx = xnew; cy = ynew; radius=3; drawcircle();
    cx = xnew; cy = ynew; radius=2; drawcircle();
    cx = xnew; cy = ynew; radius=1; drawcircle();
    firedata[lcol][lrow] = 0x2F; // prop edge c
   
    ox = 75; oy = 80; // propeller blade d
    x = 15; y = 80;
    pixelrotation();
    drawline(ox,oy,x,y);
    lcol = xnew; lrow = ynew;
    cx = xnew; cy = ynew; radius=5; drawcircle();
    cx = xnew; cy = ynew; radius=4; drawcircle();
    cx = xnew; cy = ynew; radius=3; drawcircle();
    cx = xnew; cy = ynew; radius=2; drawcircle();
    cx = xnew; cy = ynew; radius=1; drawcircle();
    firedata[lcol][lrow] = 0x3F; // prop edge d
   
    lcol = ox; lrow = oy;
    firedata[lcol][lrow] = 0x0F; // prop centre
   
    if (cycledir == 0) {
    pixcol++; pixcol++; // cycle colours
    if (pixcol > 0xFD) {cycledir = 1;}
    } else {
    pixcol--; pixcol--;
    if (pixcol < 0x2F) {cycledir = 0;}
    } // cycledir
   
    int doline = 0;
    while (doline < 145) { // copy line to shutter effect buffer
    lcol = shutterline; lrow = doline;
    shutdata[lcol][lrow] = firedata[lcol][lrow];
    doline++;
    } // doline
   
    shutterline--;
    if (shutterline < 0) {shutterline = 159;} // move rolling shutter
   
    if (shutenable == 719) {shutterline = 160;} // startup raster delay
    if (shutenable > 720) {
   
    doline = 0;
    int shuttercnt = 159;
    while(shuttercnt > shutterline) {
    doline = 0;
    while (doline < 145) { // write shutter effect buffer to screen
    lcol = shuttercnt; lrow = doline;
    firedata[lcol][lrow] = shutdata[lcol][lrow];
    doline++;
    } // doline
    shuttercnt--;
    } // shuttercnt
   
    doline = 0;
    while (doline < 285) { // moving indicator line
    lcol = shutterline - 1; lrow = doline;
    firedata[lcol][lrow] = 0xBE;
    doline++;
    } // doline
   
    } // shutenable
    shutenable++;
    if (shutenable > 9999) {shutenable = 9999;}
   
    bmpindex = 54;
    for (lrow = smlsizey-1; lrow > 0; lrow--) { // write current frame to bitmap image
    for (lcol = 0; lcol < FDATA_HEIGHT; lcol++) {
    lpixelvalue = palette[firedata[lcol][lrow]];
    imgdata[bmpindex] = (lpixelvalue >> 16) & 0xFF;
    imgdata[bmpindex+1] = (lpixelvalue >> 8) & 0xFF;
    imgdata[bmpindex+2] = lpixelvalue & 0xFF;
    bmpindex+=3;
    }}
}


[BravoV]

Hey @rt, whats the song's name for the 2nd video ?

[@rt]

Did you like it? Well guess what.... Now you’re a Twilight fan! Go team Edward!!!

Code: [Select]

    unsigned int  lrow;
    unsigned int  lcol;
    unsigned int  lpixelvalue;
    int innercnt = 0;
   
    for (lrow = smlsizey-1; lrow > 0; lrow--) { // delete previous frame from bitmap
    for (lcol = 0; lcol < FDATA_HEIGHT; lcol++) {
    lpixelvalue = 0;firedata[lcol][lrow] = 0x00;
    imgdata[bmpindex] = (lpixelvalue >> 16) & 0xFF;
    imgdata[bmpindex+1] = (lpixelvalue >> 8) & 0xFF;
    imgdata[bmpindex+2] = lpixelvalue & 0xFF;
    bmpindex+=3;
    }}
   
    int pointsx[4] = {75,75,135,15};
    int pointsy[4] = {20,140,80,80};
   
    // do propeller rotation
    int increment = 6; // must be evenly divisible by 360 at the moment
    rotation = rotation + increment;
    if (rotation > (360-increment)) {rotation = 0;}
   
    innercnt = 0;
    while (innercnt < 4) {
    ox = 75; oy = 80; // propeller blade
    x = pointsx[innercnt]; y = pointsy[innercnt];
    pixelrotation();
    drawline(ox,oy,x,y);
    lcol = xnew; lrow = ynew;
    cx = xnew; cy = ynew; radius=5; drawcircle();
    cx = xnew; cy = ynew; radius=4; drawcircle();
    cx = xnew; cy = ynew; radius=3; drawcircle();
    cx = xnew; cy = ynew; radius=2; drawcircle();
    cx = xnew; cy = ynew; radius=1; drawcircle();
    firedata[lcol][lrow] = 0x2F; // prop edge
    innercnt++;
    } // innercnt