gpumathlib_textures.cpp

这是在GPU上进行高速数字计算的数学库函数

/*******************************************************************************
**
** The header file for the gpumathlib class
** The Jahshaka Project
** Copyright (C) 2000-2004 The Jahshaka Project.
** Released under the GNU General Public License
**
*******************************************************************************/

#include "gpumathlib.h"


// build permuation/gradient table for noise
void initVertexNoiseConstants(int table_size, int*& permutation_table, float4*& gradient_table, int gradient_size)
{
    int 					i;
    int 					random_index;
    int						temp;

    permutation_table = new int[gradient_size];			// permutation table
    gradient_table = new float4[gradient_size];  			// gradient table

    // initalize random gradients
    for(i = 0; i < table_size; i++)
    {
        permutation_table[i] = i;

        gradient_table[i].x = sfrand();
        gradient_table[i].y = sfrand();
        gradient_table[i].z = sfrand();

        normalize3f(gradient_table[i].x, gradient_table[i].y, gradient_table[i].z);
    }

    // initialize permutation table (random shuffle)
    for(i = 0; i < table_size; i++)
    {
        random_index = (rand() >> 4) % table_size;
        temp = permutation_table[i];
        permutation_table[i] = permutation_table[random_index];
        permutation_table[random_index] = temp;

        gradient_table[i].w = (float)permutation_table[i];

        gradient_table[(2 * table_size) - 1 - i].x = gradient_table[i].x;
        gradient_table[(2 * table_size) - 1 - i].y = gradient_table[i].y;
        gradient_table[(2 * table_size) - 1 - i].z = gradient_table[i].z;
        gradient_table[(2 * table_size) - 1 - i].w = gradient_table[i].w;
    }
}

void create_random_texture( int width, int height, GLuint & random_texture )
{
    GLubyte* texels = new GLubyte[width * height * 4];

    int 						random;

    for( GLint y = 0; y < height; y++ )
    {
        for( GLint x = 0; x < width; x++ )
        {
            random = rand();
            texels[ (y * width * 4) + (x * 4) + 0 ] = random % 256;		// red
            texels[ (y * width * 4) + (x * 4) + 1 ] = random % 256;		// green
            texels[ (y * width * 4) + (x * 4) + 2 ] = random % 256;		// blue
            texels[ y*width*4 + x*4 + 3 ] = 255;						// alpha
        }
    }

    random_texture = 0;
    glGenTextures( 1, &random_texture );
    glBindTexture( GL_TEXTURE_2D, random_texture );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, texels );

    delete texels;
}


void create_contrast_texture( int width, int height, double density, double exponent,GLuint & contrast_texture )
{
    /* A white texture is generated. Afterwards black sprinkles are added.
    * These are shifted towards the 0 value of the y axis to archieve sort of a gradient.
    */
    GLubyte* texels = new GLubyte[width * height * 4];

    int 							x;
    int 							y;

    for( y = 0; y < height; y++ )
    {
        for( x = 0; x < width; x++ )
        {
            texels[ (y * width * 4) + (x * 4) + 0 ] = 255;				// red
            texels[ (y * width * 4) + (x * 4) + 1 ] = 255;				// green
            texels[ (y * width * 4) + (x * 4) + 2 ] = 255;				// blue
            texels[ (y * width * 4) + (x * 4) + 3 ] = 255;				// alpha
        }
    }

    for( int i = 0; i < (width * height); i++ )
    {
        x = (int)( ((double)rand()/(double)RAND_MAX) * (double)(width - 1.0) );
        y = (int)( (pow((double)rand() / (double)RAND_MAX, fabs(exponent))) * (double)(height - 1.0) );

        texels[ (y * width * 4) + (4 * x) + 0 ] = 0;
        texels[ (y * width * 4) + (4 * x) + 1 ] = 0;
        texels[ (y * width * 4) + (4 * x) + 2 ] = 0;
    }

    contrast_texture = 0;
    glGenTextures( 1, &contrast_texture );
    glBindTexture( GL_TEXTURE_2D, contrast_texture );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, texels );

    delete texels;
}