source: downloads/Samples/Water/src/WaterMesh.cpp @ 3

/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2006 Torus Knot Software Ltd
Also see acknowledgements in Readme.html

You may use this sample code for anything you like, it is not covered by the
LGPL like the rest of the engine.
-----------------------------------------------------------------------------
*/


#include "WaterMesh.h"

#define ANIMATIONS_PER_SECOND 100.0f

WaterMesh::WaterMesh(const String& meshName, Real planeSize, int complexity)
{
        int x,y,b; // I prefer to initialize for() variables inside it, but VC doesn't like it ;(

        this->meshName = meshName ;
        this->complexity =  complexity ;
        numFaces = 2 * complexity * complexity;
        numVertices = (complexity + 1) * (complexity + 1) ;
        lastTimeStamp = 0 ;
        lastAnimationTimeStamp = 0;
        lastFrameTime = 0 ;

        // initialize algorithm parameters
        PARAM_C = 0.3f ; // ripple speed
        PARAM_D = 0.4f ; // distance
        PARAM_U = 0.05f ; // viscosity
        PARAM_T = 0.13f ; // time
        useFakeNormals = false ;

        // allocate space for normal calculation
        vNormals = new Vector3[numVertices];

        // create mesh and submesh
        mesh = MeshManager::getSingleton().createManual(meshName,
        ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
        subMesh = mesh->createSubMesh();
        subMesh->useSharedVertices=false;

        // Vertex buffers
        subMesh->vertexData = new VertexData();
        subMesh->vertexData->vertexStart = 0;
        subMesh->vertexData->vertexCount = numVertices;

        VertexDeclaration* vdecl = subMesh->vertexData->vertexDeclaration;
        VertexBufferBinding* vbind = subMesh->vertexData->vertexBufferBinding;


        vdecl->addElement(0, 0, VET_FLOAT3, VES_POSITION);
        vdecl->addElement(1, 0, VET_FLOAT3, VES_NORMAL);
        vdecl->addElement(2, 0, VET_FLOAT2, VES_TEXTURE_COORDINATES);

        // Prepare buffer for positions - todo: first attempt, slow
        posVertexBuffer =
         HardwareBufferManager::getSingleton().createVertexBuffer(
            3*sizeof(float),
                        numVertices,
                        HardwareBuffer::HBU_DYNAMIC_WRITE_ONLY_DISCARDABLE);
        vbind->setBinding(0, posVertexBuffer);

        // Prepare buffer for normals - write only
        normVertexBuffer =
         HardwareBufferManager::getSingleton().createVertexBuffer(
            3*sizeof(float),
                        numVertices,
                        HardwareBuffer::HBU_DYNAMIC_WRITE_ONLY_DISCARDABLE);
        vbind->setBinding(1, normVertexBuffer);

        // Prepare texture coords buffer - static one
        // todo: optimize to write directly into buffer
        float *texcoordsBufData = new float[numVertices*2];
        for(y=0;y<=complexity;y++) {
                for(x=0;x<=complexity;x++) {
                        texcoordsBufData[2*(y*(complexity+1)+x)+0] = (float)x / complexity ;
                        texcoordsBufData[2*(y*(complexity+1)+x)+1] = 1.0f - ((float)y / (complexity)) ;
                }
        }
        texcoordsVertexBuffer =
         HardwareBufferManager::getSingleton().createVertexBuffer(
            2*sizeof(float),
                        numVertices,
                        HardwareBuffer::HBU_STATIC_WRITE_ONLY);
        texcoordsVertexBuffer->writeData(0,
                texcoordsVertexBuffer->getSizeInBytes(),
                texcoordsBufData,
                true); // true?
        delete [] texcoordsBufData;
    vbind->setBinding(2, texcoordsVertexBuffer);

        // Prepare buffer for indices
        indexBuffer =
                HardwareBufferManager::getSingleton().createIndexBuffer(
                        HardwareIndexBuffer::IT_16BIT,
                        3*numFaces,
                        HardwareBuffer::HBU_STATIC, true);
        unsigned short *faceVertexIndices = (unsigned short*)
                indexBuffer->lock(0, numFaces*3*2, HardwareBuffer::HBL_DISCARD);
        for(y=0 ; y<complexity ; y++) {
                for(int x=0 ; x<complexity ; x++) {
                        unsigned short *twoface = faceVertexIndices + (y*complexity+x)*2*3;
                        int p0 = y*(complexity+1) + x ;
                        int p1 = y*(complexity+1) + x + 1 ;
                        int p2 = (y+1)*(complexity+1) + x ;
                        int p3 = (y+1)*(complexity+1) + x + 1 ;
                        twoface[0]=p2; //first tri
                        twoface[1]=p1;
                        twoface[2]=p0;
                        twoface[3]=p2; //second tri
                        twoface[4]=p3;
                        twoface[5]=p1;
                }
        }
        indexBuffer->unlock();
        // Set index buffer for this submesh
        subMesh->indexData->indexBuffer = indexBuffer;
        subMesh->indexData->indexStart = 0;
        subMesh->indexData->indexCount = 3*numFaces;

        /*      prepare vertex positions
         *      note - we use 3 vertex buffers, since algorighm uses two last phases
         *      to calculate the next one
         */
        for(b=0;b<3;b++) {
                vertexBuffers[b] = new float[numVertices * 3] ;
                for(y=0;y<=complexity;y++) {
                        for(x=0;x<=complexity;x++) {
                                int numPoint = y*(complexity+1) + x ;
                                float* vertex = vertexBuffers[b] + 3*numPoint ;
                                vertex[0]=(float)(x) / (float)(complexity) * (float) planeSize ;
                                vertex[1]= 0 ; // rand() % 30 ;
                                vertex[2]=(float)(y) / (float)(complexity) * (float) planeSize ;
                        }
                }
        }

        AxisAlignedBox meshBounds(0,0,0,
                planeSize,0, planeSize);
        mesh->_setBounds(meshBounds);

        currentBuffNumber = 0 ;
        posVertexBuffer->writeData(0,
                posVertexBuffer->getSizeInBytes(), // size
                vertexBuffers[currentBuffNumber], // source
                true); // discard?

    mesh->load();
    mesh->touch();
}
/* ========================================================================= */
WaterMesh::~WaterMesh ()
{
        delete[] vertexBuffers[0];
        delete[] vertexBuffers[1];
        delete[] vertexBuffers[2];

        delete[] vNormals;
}
/* ========================================================================= */
void WaterMesh::push(Real x, Real y, Real depth, bool absolute)
{
        float *buf = vertexBuffers[currentBuffNumber]+1 ;
        // scale pressure according to time passed
        depth = depth * lastFrameTime * ANIMATIONS_PER_SECOND ;
#define _PREP(addx,addy) { \
        float *vertex=buf+3*((int)(y+addy)*(complexity+1)+(int)(x+addx)) ; \
        float diffy = y - floor(y+addy); \
        float diffx = x - floor(x+addx); \
        float dist=sqrt(diffy*diffy + diffx*diffx) ; \
        float power = 1 - dist ; \
        if (power<0)  \
                power = 0; \
        if (absolute) \
                *vertex = depth*power ;  \
        else \
                *vertex += depth*power ;  \
} /* #define */
        _PREP(0,0);
        _PREP(0,1);
        _PREP(1,0);
        _PREP(1,1);
#undef _PREP
}
/* ========================================================================= */
Real WaterMesh::getHeight(Real x, Real y)
{
#define hat(_x,_y) buf[3*((int)_y*(complexity+1)+(int)(_x))]
        float *buf = vertexBuffers[currentBuffNumber] ;
        Real xa = floor(x);
        Real xb = xa + 1 ;
        Real ya = floor(y);
        Real yb = ya + 1 ;
        Real yaxavg = hat(xa,ya) * (1.0f-fabs(xa-x)) + hat(xb,ya) * (1.0f-fabs(xb-x));
        Real ybxavg = hat(xa,yb) * (1.0f-fabs(xa-x)) + hat(xb,yb) * (1.0f-fabs(xb-x));
        Real yavg = yaxavg * (1.0f-fabs(ya-y)) + ybxavg * (1.0f-fabs(yb-y)) ;
        return yavg ;
}
/* ========================================================================= */
void WaterMesh::calculateFakeNormals()
{
        int x,y;
        float *buf = vertexBuffers[currentBuffNumber] + 1;
        float *pNormals = (float*) normVertexBuffer->lock(
                0,normVertexBuffer->getSizeInBytes(), HardwareBuffer::HBL_DISCARD);
        for(y=1;y<complexity;y++) {
                float *nrow = pNormals + 3*y*(complexity+1);
                float *row = buf + 3*y*(complexity+1) ;
                float *rowup = buf + 3*(y-1)*(complexity+1) ;
                float *rowdown = buf + 3*(y+1)*(complexity+1) ;
                for(x=1;x<complexity;x++) {
                        Real xdiff = row[3*x+3] - row[3*x-3] ;
                        Real ydiff = rowup[3*x] - rowdown[3*x-3] ;
                        Vector3 norm(xdiff,30,ydiff);
                        norm.normalise();
                        nrow[3*x+0] = norm.x;
                        nrow[3*x+1] = norm.y;
                        nrow[3*x+2] = norm.z;
                }
        }
        normVertexBuffer->unlock();
}
/* ========================================================================= */
void WaterMesh::calculateNormals()
{
        int i,x,y;
        float *buf = vertexBuffers[currentBuffNumber] + 1;
        // zero normals
        for(i=0;i<numVertices;i++) {
                vNormals[i] = Vector3::ZERO;
        }
        // first, calculate normals for faces, add them to proper vertices
        buf = vertexBuffers[currentBuffNumber] ;
        unsigned short* vinds = (unsigned short*) indexBuffer->lock(
                0, indexBuffer->getSizeInBytes(), HardwareBuffer::HBL_READ_ONLY);
        float *pNormals = (float*) normVertexBuffer->lock(
                0, normVertexBuffer->getSizeInBytes(), HardwareBuffer::HBL_DISCARD);
        for(i=0;i<numFaces;i++) {
                int p0 = vinds[3*i] ;
                int p1 = vinds[3*i+1] ;
                int p2 = vinds[3*i+2] ;
                Vector3 v0(buf[3*p0], buf[3*p0+1], buf[3*p0+2]);
                Vector3 v1(buf[3*p1], buf[3*p1+1], buf[3*p1+2]);
                Vector3 v2(buf[3*p2], buf[3*p2+1], buf[3*p2+2]);
                Vector3 diff1 = v2 - v1 ;
                Vector3 diff2 = v0 - v1 ;
                Vector3 fn = diff1.crossProduct(diff2);
                vNormals[p0] += fn ;
                vNormals[p1] += fn ;
                vNormals[p2] += fn ;
        }
        // now normalize vertex normals
        for(y=0;y<=complexity;y++) {
                for(x=0;x<=complexity;x++) {
                        int numPoint = y*(complexity+1) + x ;
                        Vector3 n = vNormals[numPoint] ;
                        n.normalise() ;
                        float* normal = pNormals + 3*numPoint ;
                        normal[0]=n.x;
                        normal[1]=n.y;
                        normal[2]=n.z;
                }
        }
        indexBuffer->unlock();
        normVertexBuffer->unlock();
}
/* ========================================================================= */
void WaterMesh::updateMesh(Real timeSinceLastFrame)
{
        int x, y ;

        lastFrameTime = timeSinceLastFrame ;
        lastTimeStamp += timeSinceLastFrame ;

        // do rendering to get ANIMATIONS_PER_SECOND
        while(lastAnimationTimeStamp <= lastTimeStamp) {

                // switch buffer numbers
                currentBuffNumber = (currentBuffNumber + 1) % 3 ;
                float *buf = vertexBuffers[currentBuffNumber] + 1 ; // +1 for Y coordinate
                float *buf1 = vertexBuffers[(currentBuffNumber+2)%3] + 1 ;
                float *buf2 = vertexBuffers[(currentBuffNumber+1)%3] + 1;

                /* we use an algorithm from
                 * http://collective.valve-erc.com/index.php?go=water_simulation
                 * The params could be dynamically changed every frame ofcourse
                 */
                double C = PARAM_C; // ripple speed
                double D = PARAM_D; // distance
                double U = PARAM_U; // viscosity
                double T = PARAM_T; // time
                Real TERM1 = ( 4.0f - 8.0f*C*C*T*T/(D*D) ) / (U*T+2) ;
                Real TERM2 = ( U*T-2.0f ) / (U*T+2.0f) ;
                Real TERM3 = ( 2.0f * C*C*T*T/(D*D) ) / (U*T+2) ;
                for(y=1;y<complexity;y++) { // don't do anything with border values
                        float *row = buf + 3*y*(complexity+1) ;
                        float *row1 = buf1 + 3*y*(complexity+1) ;
                        float *row1up = buf1 + 3*(y-1)*(complexity+1) ;
                        float *row1down = buf1 + 3*(y+1)*(complexity+1) ;
                        float *row2 = buf2 + 3*y*(complexity+1) ;
                        for(x=1;x<complexity;x++) {
                                row[3*x] = TERM1 * row1[3*x]
                                        + TERM2 * row2[3*x]
                                        + TERM3 * ( row1[3*x-3] + row1[3*x+3] + row1up[3*x]+row1down[3*x] ) ;
                        }
                }

                lastAnimationTimeStamp += (1.0f / ANIMATIONS_PER_SECOND);
        }

        if (useFakeNormals) {
                calculateFakeNormals();
        } else {
                calculateNormals();
        }

        // set vertex buffer
        posVertexBuffer->writeData(0,
                posVertexBuffer->getSizeInBytes(), // size
                vertexBuffers[currentBuffNumber], // source
                true); // discard?
}