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General / Lighting shader creates a bright point at the source origin.

« on: August 02, 2021, 07:03:46 pm »

I was attempting to create a lighting shader, but am having issues where there is a bright point at the center of the source (I think its because there isn't enough of a gradient). I could be missing a setting or my shader could be poorly implemented, but I'm not sure how to fix this.

Any help would be greatly appreciated.

Here is my shader
------------------------

uniform vec2 size;
uniform vec2 origin;

void main() {

    float light_strength = 1000.0;
    vec2 frag_location =  gl_FragCoord.xy;

    // Flip over the x axis
    frag_location.y = size.y - frag_location.y;

    // Get the distance from the fragment to the source
    float abs_distance = length(origin - frag_location);

    // Calculate the attenuation based on the distance
    // 1.0 / (1.0 + 1.0*d + 1.0*d^2)
    float attenuation = 1.0 / (1.0 + (1.0 * abs_distance) + (1.0 * pow(abs_distance, 2.0))) * light_strength;

    // Create a base color
    vec4 light_color = vec4(1.0, 1.0, 1.0, 1.0);

    // Change the color based on the attenuation
    vec4 color = vec4(attenuation, attenuation, attenuation, 1.0) * light_color;

    gl_FragColor = color;
}

And some example implementation code
------------------------------------------------------

    //libs: -lsfml-graphics -lsfml-system -lsfml-window

#include <SFML/Graphics.hpp>

#define width 600
#define height 600

int main() {

    sf::RenderWindow window;
    sf::Shader shader;
    sf::RenderStates states;

    window.create(sf::VideoMode(width, height), "");

    // Create a shape to fill the screen
    sf::RectangleShape fill_color(sf::Vector2f(0, 0));
    fill_color.setSize(sf::Vector2f(width, height));
    fill_color.setFillColor(sf::Color::White);

    // Shader gets compiled by whatever SFML uses for it
    shader.loadFromFile("shaders/lighting.frag", sf::Shader::Fragment);

    // Set some origin point
    shader.setUniform("size", sf::Vector2f(width, height));
    shader.setUniform("origin", sf::Vector2f(300, 300));
    states = &shader;

    while (window.isOpen()) {

        if (sf::Keyboard::isKeyPressed(sf::Keyboard::Escape)) {
            window.close();
        }

        // Draws
        window.clear();
        window.draw(fill_color, states);
        window.display();
    }
}