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struct Ray {
vec3 origin;
vec3 direction;
};
bool intersectRaySphere(out vec3 intersection, in Ray ray, in vec3 center, in float radius) {
vec3 o = center - ray.origin;
float d2 = dot(ray.direction, ray.direction);
float r2 = radius * radius;
float l2 = dot(o, o);
float dp = dot(ray.direction, o);
float delta = dp * dp / d2 - l2 + r2;
if (delta < 0.0) {
return false;
}
float lambda = dp / d2 - sqrt(delta / d2);
intersection = ray.origin + lambda * ray.direction;
return true;
}
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
vec2 uv = fragCoord.xy / iResolution.xy;
fragColor = vec4(uv,0.5+0.5*sin(iTime),1.0);
vec2 f = 0.1 * iResolution.xx/iResolution.xy;
mat3 m = mat3(
1.0, 0.0, 0.0,
0.0, 0.0, 1.0,
0.0, 1.0, 0.0
);
Ray ray = Ray(
vec3(0.0, -0.6, 0.0),
m * vec3((uv*2.0-1.0) / f, -1.0)
);
vec3 intersection;
if (intersectRaySphere(intersection, ray, vec3(0.0), 0.5)) {
fragColor = vec4(0.0);
}
}
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