spg-project/resources/background.fs

#version 430

layout (binding = 0) uniform sampler2D depthSamp;

in vec4 varShadowPosition;

out vec4 color;

void main(void) {
    vec3 pos = varShadowPosition.xyz / varShadowPosition.w;
    float shadow = float(texture(depthSamp, pos.xy).r + 0.000001 > pos.z);
    shadow = shadow * 0.6 + 0.4;
    color = vec4(0.8, 0.8, 0.8, 1.0) * shadow;
}