#version 130

#define MAX_SHADOWS 2

varying vec4 v_ShadowProjVector[MAX_SHADOWS];

uniform sampler2DShadow u_ShadowmapTexture[MAX_SHADOWS];
# define qfShadow2D(t,v) float(shadow2D(t,v))

uniform float u_ShadowAlpha;
uniform float u_ShadowProjDistance[MAX_SHADOWS];
uniform vec4 u_ShadowmapTextureParams[MAX_SHADOWS];

void main(void)
{
    float finalcolor = 1.0;

    for (int i = 0; i < MAX_SHADOWS; i++)
    {
        vec3 shadowmaptc = vec3(v_ShadowProjVector[i].xyz / v_ShadowProjVector[i].w);

        // this keeps shadows from appearing on surfaces behind frustum's nearplane
        float d = step(v_ShadowProjVector[i].w, 0.0);

        //shadowmaptc = (shadowmaptc + vec3 (1.0)) * vec3 (0.5);
        shadowmaptc.xy = shadowmaptc.xy * u_ShadowmapTextureParams[i].xy; // .x - texture width
        shadowmaptc.z = clamp(shadowmaptc.z, 0.0, 1.0);
        shadowmaptc.xy = vec2(clamp(shadowmaptc.x, 0.0, u_ShadowmapTextureParams[i].x), clamp(shadowmaptc.y, 0.0, u_ShadowmapTextureParams[i].y));

        vec2 ShadowMap_TextureScale = u_ShadowmapTextureParams[i].zw;

        float f;

        f = qfShadow2D(u_ShadowmapTexture[i], vec3(shadowmaptc.xy * ShadowMap_TextureScale, shadowmaptc.z));
       
        finalcolor *= clamp(max(max(f, d), u_ShadowAlpha), 0.0, 1.0);
    }

    gl_FragColor = vec4(vec3(finalcolor),1.0);
}