Capehill (82.128.191.210) @ 30 Jun 2005, 05:23.11

Thu, 30 Jun 2005 17:23:11 +0200
By: Capehill (82.128.191.210)
After wondering why it's so slow, I optimized the loop a bit:

--

        for ( y = 0; y < height; y++ )
        {
            // Calculate modulo outside the inner loop
            const Uint32 y_offset = y * image->pitch;

            // Uint32 _cos = (y + iter) % height;
            Uint32 _cos = y + iter;
            while ( _cos >= height )
             _cos -= height;

            // Source pixel's base address
            Uint8* src = (Uint8*)image->pixels + y_offset;

            for ( x = 0; x < width; x++ )
            {
                //Uint32 _sin = (x + iter) % width;
                Uint32 _sin = x + iter;
                while ( _sin >= width )
                 _sin -= width;

                // Calculate wave effect. It depends on wave height and sin/cos
functions
                Sint32 _x = x + ( sin_lut[ _sin ] );
                Sint32 _y = y + ( cos_lut[ _cos ] );

                // Check dimensions
                if ( _x < 0 )
                 _x = width + _x;
                else if ( _x >= width )
                    _x = _x - width;

                if ( _y < 0 )
                 _y = height + _y;
                else if ( _y >= height )
                    _y = _y - height;

                // Destinations pixel's base address
                Uint8* dest = (Uint8*)screen->pixels + _x * d_bpp + _y *
screen->pitch;

                // Red
                *(dest + dr) = *( src + sr );

                // Green
                *(dest + dg) = *( src + sg );

                // Blue
                *(dest + db) = *( src + sb );

                src += s_bpp;

            } // x

        } // y  
--

Also MAX_X & MAX_Y multiplications were move to main() where sin_lut and
cos_lut are initialized.

Optimizations give > 30% better performance.
waveeffect.lha demo/misc - Comments

Capehill (82.128.191.210) @ 30 Jun 2005, 05:23.11
