Prioritizing prefabs in array for procedural generation

Question

I am trying to create procedural space background with a bunch of sprites of nebulas and stars. I have made few prefabs with different types of sprites attached to them. I have created an array through which game will loop and randomly place different stars on a background.

The question is. I want for example 90% of white stars in the background and 10% of others. I know I can create few loops for each prefab with a different maximum number, but it doesn't look very efficient. Is there any way to prioritize some array items while looping through an array?

Answer 1

Decide your total star count. Divide it into segments. For example, out of 100 total stars:

• 10 Blue Star Hard
• 30 White Star Medium
• 60 Red Star Soft

Code:

//can make enum StarColour
int BLUE = 0;
int WHITE = 1;
int RED = 2;

//can make enum StarFocus
int HARD = 0;
int MEDIUM = 1;
int SOFT = 2;

int i = 0;
for (i = 0; i < blueHardTotal; i++)
{
    PlaceStar(BLUE, HARD);
} 

for (i = blueHardTotal; i < blueHardTotal + whiteMediumTotal; i++)
{
    PlaceStar(WHITE, MEDIUM);
} 

for (i = whiteMediumTotal; i < whiteMediumTotal + redSoftTotal; i++)
{
    PlaceStar(RED, SOFT);
} 

This takes you through index [0] to [99] in segments. P.S. There is nothing inefficient about this; and if you make the Totals compile-time constants, then the compiler should unroll the loops, thereby avoiding all conditionals.

If you want a more elegant way:

int[,] totals; //index in here by colour and focus, e.g. totals[RED, SOFT]

int i = 0;
for (int c = 0; c < COLOUR_COUNT; c++)
{
    for (int f = 0; f < FOCUS_COUNT; f++)
    {
        int max = i + totals[c, f];
        while (i < max)
        {
            PlaceStar(c, f);
            i++;
        }
    }
}