Today I wrote a simple example in shadertoy about how to apply a rotation using rotation matrices with sin and cos for a uv,
see wikipedia.
For uv I used already defined uv. I created a stripe using the modulo function to make rotation visible and completed the rotation with the iTime variable defined in shadertoy to rotate it continuously.
Here is the created source code:
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
//set the uv to a proper size on the center of screen
vec2 uv = (fragCoord - 0.5 * iResolution.xy) / min(iResolution.x, iResolution.y);
// set rotation angle value
float rot = radians(0.0);
// this set rotation by time and
rot = iTime;a
// algebra formula for rotation by matrix , https://en.wikipedia.org/wiki/Rotation_matrix
mat2 m = mat2(cos(rot), -sin(rot), sin(rot), cos(rot));
// rotation of uv with matrix algebra formula where is set the rotation angle
uv = m* uv;
// define float by function module from 1.0 and uv.x - uv.y
float d = mod(uv.x - uv.y, 1.0);
// color for fragColor is value of fload d by module function
vec4 col = vec4(vec3(d), 1.0);
fragColor = vec4(col);
}
Here is an example share from my shadertoy account.
