MNormalMapConverter.cpp

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// DESCRIPTION: 
//      Some utilities to do file format conversions and others ...
//

#include <maya/MStatus.h>
#include <math.h>
#include "MNormalMapConverter.h"


// Convert the heightfield texture to its corresponding normal map texture
//
bool MNormalMapConverter::convertToNormalMap(
                unsigned char* inImagePtr,
                unsigned int width,
                unsigned int height,
                OutFormatType outputPixelFormat,
                float bumpScale,
                unsigned char* outImagePtr )
{
        bool    isOK = true;
        
        // Firewall: The input image should not be a NULL pointer,
        //
        if( NULL == inImagePtr )        return false;
        
        // No output file specified: convert in place
        //
        if( NULL == outImagePtr )
        {
                convertToNormalMap_InPlace( inImagePtr, width, height, outputPixelFormat, bumpScale );
        }
        else
        {
                if( outputPixelFormat == RGBA ) {
                        //
                        // Not implemented yet
                        //
                        // similar to the convertToNormalMap_InPlace but we store
                        // the resulting texture in the outImagePtr and not
                        // in the inImagePtr texture
                        //
                }
                else if( outputPixelFormat == HILO ) {
                        // Not implemented yet
                }
                else {
                        isOK = false;
                }
        }

        return isOK;
}


// The heightfield texture inImage will be replaced from grey levels in RGBA
// to the normal map values as specified by the pixel format
//
bool MNormalMapConverter::convertToNormalMap_InPlace(
                unsigned char* inImagePtr,
                unsigned int width,
                unsigned int height,
                OutFormatType outputPixelFormat,
                float bumpScale )
{
        bool    isOK = true;

        if( outputPixelFormat == RGBA ) {

                bumpScale /= 255.0f;    // will be used on unsignedChar

                unsigned int widthMinus1  =  width - 1;
                unsigned int heightMinus1 = height - 1;
                unsigned int offset = (4 * width);      // = sizeof(rgba) * width

                // ==================
                // Process the texels
                // ==================

                // Get the current pointer to the starting texel at (0,0)
                //
                unsigned char* imagePtr = inImagePtr;

                // For each rows (except the last one)
                //
                unsigned int m, n;
                for( m=0; m<heightMinus1; m++ )
                {
                        // Process the texel in each column of this row
                        //
                        for( n=0; n<widthMinus1; n++ )
                        {
                                float deltaU = bumpScale * (float)(imagePtr[0] - imagePtr[4]);
                                float deltaV = bumpScale * (float)(imagePtr[0] - imagePtr[offset]);
                                
                                // Normalize (deltaU, deltaV, 1.)
                                float sqlen = deltaU*deltaU + deltaV*deltaV + 1.0f;
                                float rclen = 1.0f / sqrtf( sqlen );
                                
                                float nx = deltaU * rclen;
                                float ny = deltaV * rclen;
                                float nz = rclen;
                                
                                // Store the vector in red, green, blue
                                *(imagePtr++) = (unsigned char) ((nx + 1.0f) * 127.5f); 
                                *(imagePtr++) = (unsigned char) ((ny + 1.0f) * 127.5f); 
                                *(imagePtr++) = (unsigned char) ((nz + 1.0f) * 127.5f); 
                                
                                // reset the alpha
                                *(imagePtr++) = 255;
                        }
                        
                        // At the end of the row, just copy the last value. One
                        // could implement wraping instead.
                        *(imagePtr++) = imagePtr[-4];
                        *(imagePtr++) = imagePtr[-4];
                        *(imagePtr++) = imagePtr[-4];
                        *(imagePtr++) = 255;
                }

                // Fill in the last row (copy from the (last-1) row)
                // memcpy is the faster loop when memory is aligned.
                memcpy(imagePtr, imagePtr-offset, width*4);
        }
        else if( outputPixelFormat == HILO ) {
                // Not implemented yet
        }
        else {
                isOK = false;
        }

        return isOK;
}


bool MNormalMapConverter::convertToHeightMap(
        unsigned char* inImagePtr,
        unsigned int width,
        unsigned int height,
        OutFormatType outputPixelFormat,
        float heightScale,
        unsigned char* outImagePtr)
{
        // Not implemented yet
        //
        return false;
}