CODEWITHSUNDEEP
openglglslfractals
lhahn
lhahn

Reputation: 1241

Mandelbrot Set in a fragment shader version 330

I am trying to to make a Mandelbrot set on the fragment shader. I initially build a rectangle, and use the gl_FragCoords to calculate the algorithm. Here is the code:

#version 330 core

uniform float MaxIterations;

out vec4 pixelColor;

void main()
{
    float   real  = gl_FragCoord.x;
    float   imag  = gl_FragCoord.y;
    float   Creal = real;  
    float   Cimag = imag;  

    float r2 = 0.0;

    for (float iter = 0.0; iter < MaxIterations && r2 < 4.0; ++iter)
    {
        float tempreal = real;

        real = (tempreal * tempreal) - (imag * imag) + Creal;
        imag = 2.0 * tempreal * imag + Cimag;
        r2   = (real * real) + (imag * imag);
    }

    vec3 color;

    if (r2 < 4.0)
        color = vec3(0.0f, 0.0f, 0.0f);
    else
        color = vec3(1.0f, 1.0f, 1.0f);

    pixelColor = vec4(color, 1.0);
}

This code is actually kind of simplified and adapted version of what I found on the internet. I just assume the y axis as the imaginary and the x axis as the real part. Then I calculate the iterations until a max value passed by an uniform. It should show a black and white rectangle (white outside of the set, and black inside), but I just get a white rectangle. Does anybody knows what is wrong?

EDIT: to add a little bit more detail. Here is the vertices I used for the rectangle

GLfloat vertices[] = {
        0.9f, 0.9f,     
        0.9f, -0.9f,    
        -0.9f, -0.9f, 
        -0.9f, 0.9f 
    };

and here is the vertex shader:

#version 330 core

layout (location = 0) in vec2 position;

void main() {
    gl_Position = vec4(position, 0.0f, 1.0f);
}

Upvotes: 2

Views: 2605

Answers (1)

bofjas
bofjas

Reputation: 1206

Isn't the pixel coordinates somewhat large input values for a mandlebrot set? Try creating a new output from the vertex shader representing the vertex coordinates and use that as a input in the fragment shader:

layout (location = 0) in vec2 position;
out vec2 coord;

void main() {
    gl_Position = vec4(position, 0.0f, 1.0f);
    coord = position.xy
}

And in the fragment shader:

#version 330 core

uniform float MaxIterations;

out vec4 pixelColor;
in vec2 coord;

void main()
{
    float   real  = coord.x;
    float   imag  = coord.y;

(...)

Upvotes: 2

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