Color blending

Programming Questions

piponium

in Programming Questions • 2 years ago

hello!

I'm trying to figure out how to achieve a "blend to white" or a "blend to black" effect.

For example I have many particles flying around the screen and leaving very faint, almost transparent, purple trails behind. Instead of having the pixels show opaque purple after enough overlapping, I want them to veer to white, or to black, depending on the background colour. (Maybe they could simply veer to the inverse colour of the background?)

I've been messing around with various alpha blend settings and even tried an OPENGL hack with no success.

Your help is greatly appreciated! Thanks!

Replies(3)

nardove

Re: Color blending

2 years ago

If I understand right you just want to change the color gradually to white or black, so you can simply change the RGB values of the color to increment (go white) or decrement (go black), check out this post I comment about how to do this, you can also use the lerpColor() method or toxiclibs ColorUtils to achieve the same effect.

cedrickie..

Re: Color blending

2 years ago

sounds like a problem of the rederer to me. what renderer do you use? is your sketch 3d or 2d ?

piponium

Re: Color blending

2 years ago

Hey guys

What I'm looking for (I think) is a type of alpha blending which will make colour rich areas white or black, depending on the background.

Here is my code to make things clearer.

import processing.opengl.*;
import javax.media.opengl.GL;
GL gl;
float[] x, y, lx, ly, vx, vy;
int num = 65;
void setup() {
size(800, 494, OPENGL);
gl=((PGraphicsOpenGL)g).gl; //opengl hack
colorMode(HSB, 1.0);
smooth();
background(0);
x = new float[num]; y = new float[num];
lx = new float[num]; ly = new float[num];
vx = new float[num]; vy = new float[num];
for (int i=0; i<num; i++) {
x[i] = width/2; y[i] = height/2;
}
}
void draw() {
float f = 0.95;
float k1 = 0.01;
float k2 = 0.54;
stroke(0.73, 1.0, 1.0, 0.06);
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE); // this takes care of the blending
//blend(0, 0, width, height, 0, 0, width, height, BLEND);
for (int i=0; i<num; i++) {
lx[i] = x[i];
ly[i] = y[i];
if (i == 0) {
vx[i] += k1*(mouseX-x[i]);
vy[i] += k1*(mouseY-y[i]);
vx[i] *= f;
vy[i] *= f;
} else {
vx[i] = k2*(x[i-1]-x[i]);
vy[i] = k2*(y[i-1]-y[i]);
}
x[i] += vx[i];
y[i] += vy[i];
line(lx[i], ly[i], x[i], y[i]);
}
}

If you run the code you'll see that "denser" areas turn pink. I want them to turn white.

The openGL trick I am using was posted here on the Processing Wiki and its the closest thing I have found to what I am looking for. But it only goes as far as bright pink, not pure white.

I've seen this effect here and there but I can't seem to find any examples. I'll post an example as soon as I find one.

Any ideas?

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