<!
//  LightClusterGrid.slh
//
//  Created by Sam Gateau on 9/8/16.
//  Copyright 2013 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
!>
<@if not RENDER_LIGHT_CLUSTER_GRID_SLH@>
<@def RENDER_LIGHT_CLUSTER_GRID_SLH@>

<@include render-utils/ShaderConstants.h@>

struct FrustumGrid {
    float frustumNear;
    float rangeNear;
    float rangeFar;
    float frustumFar;
    ivec3 dims;
    float spare;
    mat4 eyeToGridProj;
    mat4 worldToEyeMat;
    mat4 eyeToWorldMat;
};

LAYOUT_STD140(binding=RENDER_UTILS_BUFFER_LIGHT_CLUSTER_FRUSTUM_GRID) uniform frustumGridBuffer {
    FrustumGrid frustumGrid;
};

float projection_getNear(mat4 projection) {
    float planeC = projection[2][3] + projection[2][2];
    float planeD = projection[3][2];
    return planeD / planeC;
}
float projection_getFar(mat4 projection) {
    //float planeA = projection[0][3] - projection[0][2]; All Zeros
    //float planeB = projection[1][3] - projection[1][2]; All Zeros
    float planeC = projection[2][3] - projection[2][2];
    float planeD = /*projection[3][3]*/ -projection[3][2];
    return planeD / planeC;
}

// glsl / C++ compatible source as interface for FrustrumGrid
<@include LightClusterGrid_shared.slh@>

// end of hybrid include

<@if GLPROFILE == MAC_GL @>
#define GRID_NUM_ELEMENTS 4096
#define GRID_INDEX_TYPE ivec4
#define GRID_FETCH_BUFFER(i) i / 4][i % 4
<@else@>
#define GRID_NUM_ELEMENTS 4096
#define GRID_INDEX_TYPE ivec4
#define GRID_FETCH_BUFFER(i) i / 4][i % 4

<!#define GRID_NUM_ELEMENTS 16384
#define GRID_INDEX_TYPE int
#define GRID_FETCH_BUFFER(i) i!>
<@endif@>

LAYOUT_STD140(binding=RENDER_UTILS_BUFFER_LIGHT_CLUSTER_GRID) uniform clusterGridBuffer {
    GRID_INDEX_TYPE _clusterGridTable[GRID_NUM_ELEMENTS];
};

LAYOUT_STD140(binding=RENDER_UTILS_BUFFER_LIGHT_CLUSTER_CONTENT) uniform clusterContentBuffer {
    GRID_INDEX_TYPE _clusterGridContent[GRID_NUM_ELEMENTS];
};

ivec3 clusterGrid_getCluster(int index) {
    int clusterDesc = _clusterGridTable[GRID_FETCH_BUFFER(index)];
    int numPointLights = 0xFF & (clusterDesc >> 16);
    int numSpotLights = 0xFF & (clusterDesc >> 24);
    int contentOffset = 0xFFFF & (clusterDesc);
    return ivec3(numPointLights, numSpotLights, contentOffset);
}

int clusterGrid_getClusterLightId(int index, int offset) {
    int elementIndex = offset + index;
    /*
    int element = _clusterGridContent[GRID_FETCH_BUFFER(elementIndex)];
    return element;
    */
    int element = _clusterGridContent[GRID_FETCH_BUFFER((elementIndex >> 1))];
    return (element >> (16 * int((elementIndex & 0x00000001) == 1))) & 0x0000FFFF;
}


<@func fetchClusterInfo(fragWorldPos)@>

    // From frag world pos find the cluster
    vec4 clusterEyePos = frustumGrid_worldToEye(<$fragWorldPos$>);
    ivec3 clusterPos = frustumGrid_eyeToClusterPos(clusterEyePos.xyz);

    ivec3 cluster = clusterGrid_getCluster(frustumGrid_clusterToIndex(clusterPos));
    int numLights = cluster.x + cluster.y;
    ivec3 dims = frustumGrid.dims.xyz;

<@endfunc@>

bool hasLocalLights(int numLights, ivec3 clusterPos, ivec3 dims) {
    return numLights>0 
        && all(greaterThanEqual(clusterPos, ivec3(0))) 
        && all(lessThan(clusterPos.xy, dims.xy))
        && clusterPos.z <= dims.z;
}

<@endif@>