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Topic: negative alpha value in fill() (Read 282 times) |
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dlb
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negative alpha value in fill()
« on: Aug 2nd, 2003, 10:48am » |
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When there is used negative alpha value in fill(), like fill(255, 0, 0, -50); then as supposed nothing apears, but when for example I'm duplicating ellipse in the same place with let's say the same parameters, then after some time shows up black ellipses making somthing similar to cloud. I used pattern sketch by REAS to prove this. try this code when moving mouse fast in practicaly one place and be patient, it will appear after some time.
I'm working on windows platform with 0056.
Edit:
The same goes to relatively small alpha values, like 0.5, and using value 5 after long mouse moving, "cloud" was far from real red color, it was like red+gray but not pure red, as it should be if ellipse has duplicated itself in one place about 200 times.
Code:
int maxSpeed;
void setup()
{
size(200, 200);
noBackground();
noStroke();
fill(102, 102, 102);
rect(0, 0, width, height);
fill(255, 0, 0, -50); // notice negative alpha value here
ellipseMode(CENTER_DIAMETER);
}
void loop()
{
if((pmouseX != 0) && (pmouseY != 0)) {
variableEllipse(mouseX, mouseY, pmouseX, pmouseY);
}
}
void variableEllipse(int x, int y, int px, int py)
{
float speed = abs(x-px) + abs(y-py);
//stroke(speed); // I commented stroke() out, so that it's easier to see black ellipse
ellipse(x, y, speed, speed);
}
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| « Last Edit: Aug 2nd, 2003, 10:57am by dlb » |
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