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Shadron Cogwheels Tutorial
#include <math_constants>
#include <multisample>
glsl struct Cogwheel {
vec2 center;
float r;
int teeth;
float toothSize;
float toothShape;
float rAxle;
int spokes;
float rotation;
float angularVel;
};
param vec2 center = vec2(0.5, 0.4);
param float r = 0.3;
param int teeth = 12;
param float toothSize = 0.03;
param float toothShape = 0.5;
param float rAxle = 0.05;
param int spokes = 6;
param float rotation = 0.0;
param float angularVel = 1.0;
param vec2 attachDirection = vec2(0.5, 1.0);
param int teeth2 = 6;
glsl float cogwheelSolid(Cogwheel c, float r, float a) {
return 1.0;
}
glsl float cogwheelSpokes(Cogwheel c, float r, float a) {
float spokes = 1.0 - step(c.toothSize + c.rAxle, abs(r*cos(0.5*float(c.spokes)*a)));
float rim = step(c.r - 3.0*c.toothSize, r);
return max(spokes, rim);
}
template <DESIGN>
glsl float sampleCogwheel(Cogwheel c, vec2 pos, float time) {
pos -= c.center;
float r = length(pos);
float a = atan(pos.x, pos.y) - (c.rotation + c.angularVel*time);
float phase = fract(0.5/PI * float(c.teeth) * a);
float toothHeight = 4.0 * abs(phase - 0.5) - 1.0;
float radius = c.r + c.toothSize * clamp(toothHeight / c.toothShape, -1.0, +1.0);
float body = 1.0 - step(radius, r);
float axle = step(c.rAxle, r);
float inside = DESIGN(c, r, a);
return min(min(body, axle), inside);
}
glsl Cogwheel attachCogwheel(Cogwheel A, vec2 direction, int teeth) {
Cogwheel B = A;
B.teeth = teeth;
float ratio = float(A.teeth)/float(B.teeth);
B.r = A.r/ratio;
B.angularVel = -ratio*A.angularVel;
B.center = A.center + (A.r+B.r)*normalize(direction);
float omega = atan(direction.x, direction.y);
B.rotation = PI + PI/float(B.teeth) - ratio*A.rotation + omega + ratio*omega;
return B;
}
glsl vec4 preview(vec2 pos) {
Cogwheel c;
c.center = center;
c.r = r;
c.teeth = teeth;
c.toothSize = toothSize;
c.toothShape = toothShape;
c.rAxle = rAxle;
c.spokes = spokes;
c.rotation = rotation;
c.angularVel = angularVel;
float sample1 = sampleCogwheel<cogwheelSpokes>(c, pos, shadron_Time);
c = attachCogwheel(c, attachDirection, teeth2);
float sample2 = sampleCogwheel<cogwheelSpokes>(c, pos, shadron_Time);
float sample = max(sample1, sample2);
return vec4(0.0, 0.0, 0.0, sample);
}
animation Preview = glsl(multisample<preview, 4>, 512, 512);
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