Bouncing Pumpkin

Eric Ludlam
/
Bouncing Pumpkin

on 9 Nov 2023

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Bounce Anything that fits in a unit sphere by remixing this!

Just be sure to parent your objects to TX, the transform objects that moves and bounces the pumpkin.

function drawframe(f)
    if f==1
        clf
        TX = hgtransform('tag','bounce');
        %% PUMPKIN
        bumps=10; bdepth=.1; bdepth2=.02; dimple=.2; width_r=1; height_r=.8;
        [ Xs, Ys, Zs ] = sphere(199);
        Rxy=(0-(1-mod(linspace(0,bumps*2,200),2)).^2)*bdepth + (0-(1-mod(linspace(0,bumps*4,200),2)).^2)*bdepth2;
        Rz = (0-linspace(1,-1,200)'.^4)*dimple;
        Xp = (width_r+Rxy).*Xs;
        Yp = (width_r+Rxy).*Ys;
        Zp = (height_r+Rz).*Zs.*(Rxy+1);
        Cp = hypot(hypot(Xp,Yp),width_r.*Zs.*(Rxy+1));
        %% STEM
        sheight=.5; scurve=.4;
        srad = [ 1.5 1 repelem(.7, 6) ] .* [ repmat([.1 .06],1,bumps) .1 ]';
        [theta, phi] = meshgrid(linspace(0,pi/2,size(srad,2)),linspace(0,2*pi,size(srad,1)));
        Xs = (scurve-cos(phi).*srad).*cos(theta)-scurve;
        Zs = (sheight-cos(phi).*srad).*sin(theta) + height_r-max(0,dimple*.9);
        Ys = -sin(phi).*srad;
        surf(Xp,Yp,Zp,Cp,'parent',TX);
        shading interp
        colormap([ linspace(.94, 1, 256); linspace(.37, .46, 256); linspace(0, .1, 256) ]');
        surface(Xs,Ys,Zs,[],'FaceColor', '#008000', 'EdgeColor','none', 'Parent',TX);
        material([ .6, .9, .3, 2, .5 ])
        lighting g
        %% Axes setup
        axis([-2 2 -2 2 1.75 7.8])
        daspect([1 1 1])
        view(3)
        set(gca,'clipping','off','visible','off','xdir','r');
        light('position',[ 0 -10 5],'style','local');
        %% Motion Context
        ctxt.Z = 9;
        ctxt.Q = 0;
        ctxt.Zv = 0;
        ctxt.B = 0;
        setappdata(gcf,'ctxt',ctxt);
    else
        TX = findobj('tag','bounce');
    end
    ctxt = getappdata(gcf,'ctxt');
    %% Compute cheap-o velocity, bounce, and squish
    ctxt.Zv=ctxt.Zv+.032; % Cheap Gravity
    ctxt.Z=ctxt.Z-ctxt.Zv; % Motion
    if ctxt.Z<0 % bounce!
        ctxt.Z=ctxt.Zv+ctxt.Z; % Push up by amount pushed below
        ctxt.Zv = -ctxt.Zv;
        ctxt.Q = 1;
    end
    
    ctxt.B = ctxt.B + 1/4;
    bounce=cospi(ctxt.B);
    ctxt.Q=max(ctxt.Q-.036,0); % Q tracks the magnitude of squish
    bscale = (ctxt.Q*bounce)/2;
    %% Create transform to move and squish the pumpkin
    set(TX, 'Matrix', makehgtform('translate',[0 0 ctxt.Z], 'scale', [1+bscale 1+bscale 1-bscale]));
    
    setappdata(gcf,'ctxt',ctxt);
end