OpenGL Fragment Shaders | How Do Fragment Shaders Work?

How are fragment shaders actually working?
More than one color on screen?
Why so difficult?

This series is based off of the free on-line book, "The Book Of Shaders", by Patricio Gonzalez Vivo and Jen Lowe.
https://thebookofshaders.com/
If you feel like donating, please donate to those two; a donation link is found on their website linked above.

Previous video: https://www.bitchute.com/video/jLw0jBL9znVv/

Editor used: https://patriciogonzalezvivo.github.io/glslEditor/

Code used:

1.

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;

void main() {
vec2 st = gl_FragCoord.xy/u_resolution;

if (st.x >= 0.500 && st.x <= 0.503 && st.y >= 0.500 && st.y <= 0.503) {
gl_FragColor = vec4(1.,1.0,1.0,1.0);
} else {
gl_FragColor = vec4(0.,0.0,0.0,1.0);
}
}

2.

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;

void main() {
vec2 st = gl_FragCoord.xy/u_resolution;
vec3 canvas = vec3(1.0);

canvas = mix(canvas, vec3(1.0,0.0,0.0), st.x);
gl_FragColor = vec4(canvas, 1.0);
}

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