Firstly, don’t use magic numbers such as “0.0039215686274509803921568627451”.
Use:

float scale = 1.0 / 255.0;

Secondly are you aware that DitherByChance() returns values from the range of 0-255?
Reading from the texture in the shader gives you a value between 0 and 1.
Then you multiply that by 255.
For example, if the texture gave you 0.52 for red as per your example, you then do the following to it:

double rPercentChance = frac(oldColor.r / scale);

Which evaluates to the following:

double rPercentChance = frac(0.52 / 0.0039215686274509803921568627451);

Which evaluates to:

double rPercentChance = frac(132.59999999999999999999999999993);

Is this what you were expecting?
If so, why would you not just do:

double rPercentChance = frac(oldColor.r * 255.0);

instead?  Multiplication is faster than division.


L. Spiro

Firstly, don’t use magic numbers such as “0.0039215686274509803921568627451”.
Use:

float scale = 1.0 / 255.0;

Secondly are you aware that DitherByChance() returns values from the range of 0-255?
Reading from the texture in the shader gives you a value between 0 and 1.
Then you multiply that by 255.
For example, if the texture gave you 0.52 for read as per your example, you then do the following to it:

double rPercentChance = frac(oldColor.r / scale);

Which evaluates to the following:

double rPercentChance = frac(0.52 / 0.0039215686274509803921568627451);

Which evaluates to:

double rPercentChance = frac(132.59999999999999999999999999993);

Is this what you were expecting?
If so, why would you not just do:

double rPercentChance = frac(oldColor.r * 255.0);

instead?  Multiplication is faster than division.


L. Spiro

Firstly, don’t use magic numbers such as “0.0039215686274509803921568627451”.
Use:

float scale = 1.0 / 255.0;

Secondly are you aware that DitherByChance() returns values from the range of 0-255?
Reading from the texture in the shader gives you a value between 0 and 1.
Then you multiply that by 255.
For example, if the texture gave you 0.52 for read as per your example, you then do the following to it:

double rPercentChance = frac(oldColor.r / scale);

Which evaluates to the following:

double rPercentChance = frac(0.52 / 0.0039215686274509803921568627451);

Which evaluates to:

double rPercentChance = frac(132.59999999999999999999999999993);

Is this what you were expecting?


L. Spiro