void *tx = RiCreateTexture(0, 0, 0, 256, 256, 0);

     int k = 0;
     unsigned char *p = new unsigned char[256 * 256 * 3];
     for(int i = 0; i < 256; i++)
     {
         for(int j = 0; j < 256; j++)
         {
             int c = ((((i&0x8)==0)^((j&0x8))==0))*255;
             p[k++] = c;
             p[k++] = c;
             p[k++] = c;
         }
     }

     RiTextureSetPixels(tx, p);
     RiEntityTexture(model, tx, 0);