Things I learned :

• Shader is executed in the GPU which are tiny microprocessors running in parallel at the same time. That’s why it can be fast.

• Each thread in the GPU is blind and memoryless. (impossible to know the previous state)

• The final pixel color is assigned to the reserved global variable gl_FragColor.

• vec3 + float can be used to construct vec4: vec4(vec3(1.0,0.0,1.0),1.0);

• uniform: bridges between the CPU and the GPU

• Some of the built-in uniforms

uniform vec2 u_resolution;  // Canvas size (width,height)
uniform vec2 u_mouse;       // mouse position in screen pixels
uniform float u_time;       // Time in seconds since load

• Uniform are variables that globally applies to every pixel whereas Varying are different from pixel to pixel (or thread to thread)

• Bottom is 0 in Y coordinate.

Questions and comments :

• floating point suffix is not supported? 0.0f isn’t 1.0 double?

• 1. what is the default precision for float? (or any type)

• below7. Try commenting out line 6? -> line 6 doesn’t exist

• ofRect is deprecated.

Development environment setup

For now, I decided to use openFrameworks in Pd (using the Ofelia external) to load/run shader code.

Tags

#make20 #20daysITP