in vec3 v_position;
out vec4 fragcolor;

const int SHADOW_VSM = 0;
const int SHADOW_CSM = 1;

uniform int shadow_technique;

void main() {
    if (shadow_technique == SHADOW_VSM) {
        float depth = length(v_position) / 200;

        float moment1 = depth;
        float moment2 = depth * depth;
        
        float dx = dFdx(depth);
        float dy = dFdy(depth);
        moment2 += 0.25*(dx*dx+dy*dy);
        fragcolor = vec4( moment1, moment2, 0.0, 1.0);
    }
    else if (shadow_technique == SHADOW_CSM) {
        fragcolor = vec4(vec3(gl_FragCoord.z), 1.0);
    }
}