[WS2801] Stuck in animation for LED strip

Projects General Guidance
1

Hello,

I am experimenting with WS2801 type LED-strips.
Having LEDs lit in specific colors works fine. However, I am stuck in making animations.

I want to light up specific sections (called 'strands' in my code).
Virtually I split the LED strip up to 14 sections of 9 LEDs per section.

I want section 1 (or 0 however you like to call it) to fade on to 100% brightness, with speed which could be defined in a variable. Right now, I use a delay(1), and the fading is to slow now.
Also, I guess I should not use delay. Why? Because I dont want to wait for section one to lit up completely. I want section 2 starting to fade short before section 1 is finished, so I gives an almost smooth transition.

And after all sections have been lit up, wait for 2 full seconds, and start to fade out in the exact same way.

Short: The sections should fade in one section at a time from left to right, and 2 seconds after they all lit up, start fade out from left to right, one section at a time. (With being able to start next section transition while the active one is not completely finished yet)

My actual code:

// Initialize libraries
#include "Adafruit_WS2801.h"
#include "SPI.h"

#define NUM_LEDS 128
#define STRANDS 14

#define DATA_PIN 5
#define CLOCK_PIN 6

// Initialize LED strip
Adafruit_WS2801 strip = Adafruit_WS2801(NUM_LEDS, DATA_PIN, CLOCK_PIN);

// Variables
int ledsPerStrain = 0;

// Initialize
void setup(){
	ledsPerStrain = (NUM_LEDS/STRANDS); // Current outcome: 9 LEDs per strand
	bootSequence();
}

// Run application
void loop() {
	runAnimation(0, 0, 255, 1);
}

void bootSequence(){
	strip.begin(); // Initialize strip
	strip.show(); // Empty strip

	// TODO: Create boot sequence (self-test) animation
}

void runAnimation(uint8_t red, uint8_t green, uint8_t blue, uint8_t wait) {
	unsigned long currentMillis = millis();

	//
	// Turn on all strands
	//
	for(uint8_t s=0; s < STRANDS; s++){
		for(uint8_t b=0; b <255; b++) {
			for(uint8_t i=(s*ledsPerStrain); i < ((s*ledsPerStrain)+ledsPerStrain); i++) {
				strip.setPixelColor(i, red*b/255, green*b/255, blue*b/255);
			}
			strip.show();
			delay(wait);
		}
	}
	delay(2000); // Wait 2 seconds after everything is lit

	//
	// Turn off all strands
	//
	for(uint8_t s=0; s < STRANDS; s++){
		for(uint8_t b=0; b <255; b--) {
			for(uint8_t i=(s*ledsPerStrain); i < ((s*ledsPerStrain)+ledsPerStrain); i++) {
				strip.setPixelColor(i, red*b/255, green*b/255, blue*b/255);
			}
			strip.show();
			delay(wait);
		}
	}
	delay(2000); // Wait 2 seconds after everything went dark
};

// Create a 24 bit color value from R,G,B
uint32_t Color(byte r, byte g, byte b){
	uint32_t c;
	c = r;
	c <<= 8;
	c |= g;
	c <<= 8;
	c |= b;
	return c;
}
2

Anyone?