/*

     File: RippleModel.m

 Abstract: Ripple model class that simulates the ripple effect.

  Version: 1.0

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#import "RippleModel.h"

@interface RippleModel () {

    unsigned int screenWidth;

    unsigned int screenHeight;

    unsigned int poolWidth;

    unsigned int poolHeight;

    unsigned int touchRadius;

    unsigned int meshFactor;

    float texCoordFactorS;

    float texCoordOffsetS;

    float texCoordFactorT;

    float texCoordOffsetT;

    // ripple coefficients

    float *rippleCoeff;

    // ripple simulation buffers

    float *rippleSource;

    float *rippleDest;

    // data passed to GL

    GLfloat *rippleVertices;

    GLfloat *rippleTexCoords;

    GLushort *rippleIndicies;    

}

@end

@implementation RippleModel

- (void)initRippleMap

{

    // +2 for padding the border

    memset(rippleSource, 0, (poolWidth+2)*(poolHeight+2)*sizeof(float));

    memset(rippleDest, 0, (poolWidth+2)*(poolHeight+2)*sizeof(float));

}

- (void)initRippleCoeff

{

    for (int y=0; y<=2*touchRadius; y++)

    {

        for (int x=0; x<=2*touchRadius; x++)

        {        

            float distance = sqrt((x-touchRadius)*(x-touchRadius)+(y-touchRadius)*(y-touchRadius));

            if (distance <= touchRadius)

            {

                float factor = (distance/touchRadius);

                // goes from -512 -> 0

                rippleCoeff[y*(touchRadius*2+1)+x] = -(cos(factor*M_PI)+1.f) * 256.f;

            }

            else 

            {

                rippleCoeff[y*(touchRadius*2+1)+x] = 0.f;   

            }

        }

    }    

}

- (void)initMesh

{

    for (int i=0; i<poolHeight; i++)

    {

        for (int j=0; j<poolWidth; j++)

        {

            rippleVertices[(i*poolWidth+j)*2+0] = -1.f + j*(2.f/(poolWidth-1));

            rippleVertices[(i*poolWidth+j)*2+1] = 1.f - i*(2.f/(poolHeight-1));

            rippleTexCoords[(i*poolWidth+j)*2+0] = (float)i/(poolHeight-1) * texCoordFactorS + texCoordOffsetS;

            rippleTexCoords[(i*poolWidth+j)*2+1] = (1.f - (float)j/(poolWidth-1)) * texCoordFactorT + texCoordFactorT;

        }            

    }

    unsigned int index = 0;

    for (int i=0; i<poolHeight-1; i++)

    {

        for (int j=0; j<poolWidth; j++)

        {

            if (i%2 == 0)

            {

                // emit extra index to create degenerate triangle

                if (j == 0)

                {

                    rippleIndicies[index] = i*poolWidth+j;

                    index++;                    

                }

                rippleIndicies[index] = i*poolWidth+j;

                index++;

                rippleIndicies[index] = (i+1)*poolWidth+j;

                index++;

                // emit extra index to create degenerate triangle

                if (j == (poolWidth-1))

                {

                    rippleIndicies[index] = (i+1)*poolWidth+j;

                    index++;                    

                }

            }

            else

            {

                // emit extra index to create degenerate triangle

                if (j == 0)

                {

                    rippleIndicies[index] = (i+1)*poolWidth+j;

                    index++;

                }

                rippleIndicies[index] = (i+1)*poolWidth+j;

                index++;

                rippleIndicies[index] = i*poolWidth+j;

                index++;

                // emit extra index to create degenerate triangle

                if (j == (poolWidth-1))

                {

                    rippleIndicies[index] = i*poolWidth+j;

                    index++;

                }

            }

        }

    }

}

- (GLfloat *)getVertices

{

    return rippleVertices;

}

- (GLfloat *)getTexCoords

{

    return rippleTexCoords;

}

- (GLushort *)getIndices

{

    return rippleIndicies;

}

- (unsigned int)getVertexSize

{

    return poolWidth*poolHeight*2*sizeof(GLfloat);

}

- (unsigned int)getIndexSize

{

    return (poolHeight-1)*(poolWidth*2+2)*sizeof(GLushort);

}

- (unsigned int)getIndexCount

{

    return [self getIndexSize]/sizeof(*rippleIndicies);

}

- (void)freeBuffers

{

    free(rippleCoeff);

    free(rippleSource);

    free(rippleDest);

    free(rippleVertices);

    free(rippleTexCoords);

    free(rippleIndicies);    

}

- (id)initWithScreenWidth:(unsigned int)width

             screenHeight:(unsigned int)height

               meshFactor:(unsigned int)factor

              touchRadius:(unsigned int)radius

             textureWidth:(unsigned int)texWidth

            textureHeight:(unsigned int)texHeight

{

    self = [super init];

    if (self)

    {

        screenWidth = width;

        screenHeight = height;

        meshFactor = factor;

        poolWidth = width/meshFactor;

        poolHeight = height/meshFactor;

        touchRadius = radius;

        if ((float)screenHeight/screenWidth < (float)texWidth/texHeight)

        {            

            texCoordFactorS = (float)(texHeight*screenHeight)/(screenWidth*texWidth);            

            texCoordOffsetS = (1.f - texCoordFactorS)/2.f;

            texCoordFactorT = 1.f;

            texCoordOffsetT = 0.f;

        }

        else

        {

            texCoordFactorS = 1.f;

            texCoordOffsetS = 0.f;            

            texCoordFactorT = (float)(screenWidth*texWidth)/(texHeight*screenHeight);

            texCoordOffsetT = (1.f - texCoordFactorT)/2.f;

        }

        rippleCoeff = (float *)malloc((touchRadius*2+1)*(touchRadius*2+1)*sizeof(float));

        // +2 for padding the border

        rippleSource = (float *)malloc((poolWidth+2)*(poolHeight+2)*sizeof(float));

        rippleDest = (float *)malloc((poolWidth+2)*(poolHeight+2)*sizeof(float));

        rippleVertices = (GLfloat *)malloc(poolWidth*poolHeight*2*sizeof(GLfloat));

        rippleTexCoords = (GLfloat *)malloc(poolWidth*poolHeight*2*sizeof(GLfloat));

        rippleIndicies = (GLushort *)malloc((poolHeight-1)*(poolWidth*2+2)*sizeof(GLushort));

        if (!rippleCoeff || !rippleSource || !rippleDest || 

            !rippleVertices || !rippleTexCoords || !rippleIndicies)

        {

            [self freeBuffers];

            return nil;

        }

        [self initRippleMap];

        [self initRippleCoeff];

        [self initMesh];

    }

    return self;

}

- (void)runSimulation

{

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    // first pass for simulation buffers...

    dispatch_apply(poolHeight, queue, ^(size_t y) {

        for (int x=0; x<poolWidth; x++)

        {

            // * - denotes current pixel

            //

            //       a 

            //     c * d

            //       b 

            // +1 to both x/y values because the border is padded

            float a = rippleSource[(y)*(poolWidth+2) + x+1];

            float b = rippleSource[(y+2)*(poolWidth+2) + x+1];

            float c = rippleSource[(y+1)*(poolWidth+2) + x];

            float d = rippleSource[(y+1)*(poolWidth+2) + x+2];

            float result = (a + b + c + d)/2.f - rippleDest[(y+1)*(poolWidth+2) + x+1];

            result -= result/32.f;

            rippleDest[(y+1)*(poolWidth+2) + x+1] = result;

        }            

    });

    // second pass for modifying texture coord

    dispatch_apply(poolHeight, queue, ^(size_t y) {

        for (int x=0; x<poolWidth; x++)

        {

            // * - denotes current pixel

            //

            //       a

            //     c * d

            //       b

            // +1 to both x/y values because the border is padded

            float a = rippleDest[(y)*(poolWidth+2) + x+1];

            float b = rippleDest[(y+2)*(poolWidth+2) + x+1];

            float c = rippleDest[(y+1)*(poolWidth+2) + x];

            float d = rippleDest[(y+1)*(poolWidth+2) + x+2];

            float s_offset = ((b - a) / 2048.f);

            float t_offset = ((c - d) / 2048.f);

            // clamp

            s_offset = (s_offset < -0.5f) ? -0.5f : s_offset;

            t_offset = (t_offset < -0.5f) ? -0.5f : t_offset;

            s_offset = (s_offset > 0.5f) ? 0.5f : s_offset;

            t_offset = (t_offset > 0.5f) ? 0.5f : t_offset;

            float s_tc = (float)y/(poolHeight-1) * texCoordFactorS + texCoordOffsetS;

            float t_tc = (1.f - (float)x/(poolWidth-1)) * texCoordFactorT + texCoordOffsetT;

            rippleTexCoords[(y*poolWidth+x)*2+0] = s_tc + s_offset;

            rippleTexCoords[(y*poolWidth+x)*2+1] = t_tc + t_offset;

        }

    });

    float *pTmp = rippleDest;

    rippleDest = rippleSource;

    rippleSource = pTmp;    

}

- (void)initiateRippleAtLocation:(CGPoint)location

{

    unsigned int xIndex = (unsigned int)((location.x / screenWidth) * poolWidth);

    unsigned int yIndex = (unsigned int)((location.y / screenHeight) * poolHeight);

    for (int y=(int)yIndex-(int)touchRadius; y<=(int)yIndex+(int)touchRadius; y++)

    {

        for (int x=(int)xIndex-(int)touchRadius; x<=(int)xIndex+(int)touchRadius; x++)

        {        

            if (x>=0 && x<poolWidth &&

                y>=0 && y<poolHeight)

            {

                // +1 to both x/y values because the border is padded

                rippleSource[(poolWidth+2)*(y+1)+x+1] += rippleCoeff[(y-(yIndex-touchRadius))*(touchRadius*2+1)+x-(xIndex-touchRadius)];   

            }

        }

    }    

}

- (void)dealloc

{

    [self freeBuffers];

}

@end