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/*
 * Copyright (c) 2009-2021 jMonkeyEngine
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */
package com.jme3.util.mikktspace;

/**
 *
 * @author Nehon
 */
public interface MikkTSpaceContext {

    /**
     * Returns the number of faces (triangles/quads) on the mesh to be
     * processed.
     *
     * @return the count (≥0)
     */
    public int getNumFaces();

    /**
     * Returns the number of vertices on face number iFace iFace is a number in
     * the range {0, 1, ..., getNumFaces()-1}
     *
     * @param face which face (≥0, <numFaces)
     * @return the count (≥0)
     */
    public int getNumVerticesOfFace(int face);

    /**
     * returns the position/normal/texcoord of the referenced face of vertex
     * number iVert. iVert is in the range {0,1,2} for triangles and {0,1,2,3}
     * for quads.
     *
     * @param posOut storage for the results (modified)
     * @param face which face (≥0, <numFaces)
     * @param vert which vertex in the face (≥0, <numVertices)
     */
    public void getPosition(float posOut[], int face, int vert);

    public void getNormal(float normOut[], int face, int vert);

    public void getTexCoord(float texOut[], int face, int vert);

    /**
     * The callback setTSpaceBasic() is sufficient for basic normal mapping.
     * This function is used to return the tangent and sign to the application.
     * tangent is a unit length vector. For normal maps it is sufficient to use
     * the following simplified version of the bitangent which is generated at
     * pixel/vertex level.
     *
     * bitangent = fSign * cross(vN, tangent);
     *
     * Note that the results are returned unindexed. It is possible to generate
     * a new index list But averaging/overwriting tangent spaces by using an
     * already existing index list WILL produce INCORRECT results. DO NOT! use
     * an already existing index list.
     *
     * @param tangent the desired tangent vector (unaffected)
     * @param sign the desired sign
     * @param face which face (≥0, <numFaces)
     * @param vert which vertex in the face (≥0, <numVertices)
     */
    public void setTSpaceBasic(float tangent[], float sign, int face, int vert);

    /**
     * This function is used to return tangent space results to the application.
     * tangent and biTangent are unit length vectors and fMagS and fMagT are
     * their true magnitudes which can be used for relief mapping effects.
     *
     * biTangent is the "real" bitangent and thus may not be perpendicular to
     * tangent. However, both are perpendicular to the vertex normal. For normal
     * maps it is sufficient to use the following simplified version of the
     * bitangent which is generated at pixel/vertex level.
     *
     *      * fSign = bIsOrientationPreserving ? 1.0f : (-1.0f);
     * bitangent = fSign * cross(vN, tangent);
     * 
     *
     * Note that the results are returned unindexed. It is possible to generate
     * a new index list. But averaging/overwriting tangent spaces by using an
     * already existing index list WILL produce INCORRECT results. DO NOT! use
     * an already existing index list.
     *
     * @param tangent the desired tangent vector (unaffected)
     * @param biTangent the desired bitangent vector (unaffected)
     * @param magS true magnitude of S
     * @param magT true magnitude of T
     * @param isOrientationPreserving true→preserves, false→doesn't
     * preserve
     * @param face which face (≥0, <numFaces)
     * @param vert which vertex in the face (≥0, <numVertices)
     */
    void setTSpace(float tangent[], float biTangent[], float magS, float magT,
            boolean isOrientationPreserving, int face, int vert);
}