I need help with my fragment shader

Questions
#1

i’m trying to convert the rgb to YCbCr for better color manipulation, but i can’t seem to figure it out.

const float Kr = 0.299;
const float Kg = 0.587;
const float Kb = 0.114;

void main()
{
	lowp vec4 tex = texture2D(texture_sampler, var_texcoord0.xy);
	vec4 tempfrag = tex * var_color;

	vec3 newcol=RGBtoYCBCR( vec3(tempfrag.x,tempfrag.y,tempfrag.z) );
}

vec3 RGBtoYCBCR(vec3 rgbcolor)
{
	float y=0.0;
	float Cb=0.0;
	float Cr=0.0;
	float r=rgbcolor.x;
	float g=rgbcolor.y;
	float b=rgbcolor.z;

	y=r*Kr+g*Kg+b*Kb;
	Cb=-0.5*(Kr/(1.0-Kb))*r -0.5*(Kg/(1.0-Kb))*g + 0.5*b  ;
	Cr=0.5*r -0.5*(Kg/(1.0-Kr))*g -0.5*(Kb/(1.0-Kr))*b; ;
return vec3(y,Cb,Cr);
}

it just spits some errors out, and i don’t really get why. i don’t see anywhere in my code that i’m converting a const float to a vec3.

Compatability issue: _generated_1951c3df.fpc2333632367242982588.glsl:          "precision mediump int; precision highp float;" 
_generated_1951c3df.fpc2333632367242982588.glsl:25: error: 'RGBtoYCBCR' : no matching overloaded function found
_generated_1951c3df.fpc2333632367242982588.glsl:25: error: '=' :  cannot convert from ' const float' to ' temp highp 3-component vector of float'
#2

wait, can fragment constants even be used (changed) within the GUI?

#3

Yes, it should be possible. You can send constants to your shader in the render.draw() call. Also note that you can use multiple materials in a GUI node nowadays.

#4

You can send constants to your shader in the render.draw() call.

ok. i notice that the function renders all things with the material tag, is there a way to render one node at a time, since i’ll need them to have different parameters?
if not i can go with the lazy approach and just make a separate material for each (i know there will only be a small amount of nodes i need to do this on).

#5

Why don’t you use fragment paramenters instead of constants? that way you can change them on a sprite basis in a script. (If I understand correctly what you are trying to do…)

#6

that way you can change them on a sprite basis in a script

because i’m not using sprites, i’m using gui nodes

1 Like