Create a 3D space

I have written a code that animates 2d dots moving in a certain direction. I tried to create a 3rd dimension using spherical coordinates, and for that I used two times the psychtoolbox function Screen(‘DrawDots’)that takes only 2D coordinates - so I used it first for X and Y and then for X and Z, but it does not give a proper 3D perception. Therefore I used moglDrawDots3D instead, as it takes 3d coordinates XYZ, but the dots appear and disappear instead of moving all in a given direction. I have no clue on the cause. I am very new to Matlab and animations, I'd be very grateful to get your feedback and insight. I tried to explain my code step by step below for the sake of clarity. Thank you in advance for your help!

InitializeMatlabOpenGL;

dots.nDots = 100; % number of dots

dots.color = [255,255,255]; % color of the dots

dots.size = 10; % size of dots (pixels)

dots.center = [0,0,0]; % center of the field of dots (x,y,z)

dots.apertureSize = [12,12,60]; % size of rectangular aperture [w,h,depth] in degrees

First, I defined a random position within the aperture for each of the dots. 'dots.x' and 'dots.y' will hold the x and y positions for each dot.

dots.x = (rand(1,dots.nDots))*dots.apertureSize(1) + dots.center(1); %'rand(dots.nDots,1)' generates a vector dots.nDots long of random numbers between 0 and 1.

dots.y = (rand(1,dots.nDots))*dots.apertureSize(2) + dots.center(2); % To change that range to fit the aperture we multiply them by the aperture size, and add the center offset.

dots.z = (rand(1,dots.nDots))*dots.apertureSize(3) + dots.center(3);

Then I converted these dot positions from a visual angle into pixel coordinates using a created function 'angle2pix'

tmp = Screen('Resolution',0); % (1) Screen's 'Resolution' function determine the screen resolution.

display.resolution = [tmp.width,tmp.height];

display.width = 30; % (2) Width of the screen in cm (with a ruler).

display.dist = 50; % (3) Distance of the screen from the observer in cm.

% This generates pixel positions, but they're centered at [0,0], which is the top left corner

pixpos.x = angle2pix(display,dots.x); % Convert the x position of the dots from visual angle to pixel.

pixpos.y = angle2pix(display,dots.y); % Convert the y position of the dots from visual angle to pixel.

pixpos.z = angle2pix(display,dots.z); % Convert the z position of the dots from visual angle to pixel.

I defined some timing and motion parameters for the animation

dots.speed = 3; %degrees/second

dots.duration = 5; %seconds

dots.theta_deg = 30; %degrees

dots.phi_deg = 100; %degrees

dots.theta_rad = dots.theta_deg * pi /180; % direction converted to radians

dots.phi_rad = dots.phi_deg * pi /180; % direction converted to radians

I calculated the distance travelled by the dot, by determining the x,y and z positions using spherical coordinates and then their derivate.

dx = dots.speed* sin(-dots.phi_rad-dots.theta_rad)/display.frameRate;

dy = -dots.speed* cos(dots.phi_rad + dots.theta_rad)/display.frameRate;

dz = -dots.speed*cos(dots.theta_rad)/display.frameRate;

The total number of frames for the animation is determined by the duration (seconds) multiplied by the frame rate (frames/second). The function secs2frames performs the calculation

nFrames = secs2frames(display,dots.duration);

I try to fit the dots within the aperture by calculating the left, right top, bottom and depth(forward and backward) of the aperture (in degrees)

l = dots.center(1)-dots.apertureSize(1)/2;

r = dots.center(1)+dots.apertureSize(1)/2;

b = dots.center(2)-dots.apertureSize(2)/2;

t = dots.center(2)+dots.apertureSize(2)/2;

d_forward = dots.center(3)- dots.apertureSize(3)/2;

d_backward = dots.center(3)+ dots.apertureSize(3)/2;

New random starting positions

dots.x = (rand(1,dots.nDots))*dots.apertureSize(1) + dots.center(1);

dots.y = (rand(1,dots.nDots))*dots.apertureSize(2) + dots.center(2);

dots.z = (rand(1,dots.nDots))*dots.apertureSize(3) + dots.center(3);

Make the dots move

try

for i=1:nFrames

%convert from degrees to screen pixels

pixpos.x = angle2pix(display,dots.x)+ display.resolution(1)/2;

pixpos.y = angle2pix(display,dots.y)+ display.resolution(2)/2;

pixpos.z = angle2pix(display,dots.z)+ display.resolution(2)/2;

I commented the function screen drawdots that I previously used.

% Screen('DrawDots',display.windowPtr,[pixpos.x;pixpos.y], dots.size, dots.color,[0,0],1);

% Screen('DrawDots',display.windowPtr,[pixpos.x;pixpos.z], dots.size, dots.color,[0,0],1);

I replaced Screen DrawDots with moglDrawDots3D

moglDrawDots3D(display.windowPtr, [pixpos.x;pixpos.y;pixpos.z],dots.size, dots.color, dots.center);

%update the dot position

dots.x = dots.x + dx;

dots.y = dots.y + dy;

dots.z = dots.z + dz;

%move the dots that are outside the aperture back on aperture

dots.x(dots.x<l) = dots.x(dots.x<l) + dots.apertureSize(1);

dots.x(dots.x>r) = dots.x(dots.x>r) - dots.apertureSize(1);

dots.y(dots.y<b) = dots.y(dots.y<b) + dots.apertureSize(2);

dots.y(dots.y>t) = dots.y(dots.y>t) - dots.apertureSize(2);

dots.z(dots.z<d_forward) = dots.z(dots.z<d_forward) + dots.apertureSize(3);

dots.z(dots.z>d_backward) = dots.z(dots.z>d_backward) -dots.apertureSize(3);

Screen('Flip',display.windowPtr);

end

catch ME

Screen('CloseAll');

rethrow(ME)

end

Screen('CloseAll');