linear gradients

derive_color.metal

float4 derive_color(float2 pixel_pos, float2 start, float2 end, float4 start_color, float4 end_color) {
   float2 adjusted_end = end - start;
   float h = dot(pixel_pos - start, adjusted_end) / dot(adjusted_end, adjusted_end);
   return mix(start_color, end_color, h);
}