/*
Using Texture Subloading As an Alternative For Drawpixels
By Jaya Kanajan, SGI

H1. Introduction:

DCC applications often rely heavily on glDrawPixels in order to transfer their
generated images to the screen, such as during the playback of video clips.
glDrawPixels performance varies substantially in range across commodity
graphics implementations. However, texture download performance is often well
optimized due to it's use by many popular games. As a result, it can be
preferable for ISVs to use texture subloading to achieve the same effect. By
using texture subloading, various effects that were unavailable with
glDrawPixels can be achieved. For example, sequence switching effects like
fading in and out are made simpler using textures and geometry (think
multitexture for fading). The ability to allow the user to dynamically adjust
the window size without needing to scale the data is very useful. Being able to
dynamically switch back and forth between ranges of frames by using texture
objects avoids the overhead of redownloading data that is necessary if using
glDrawPixels.

H1. Details
In the following example, the buffers (to be thought of as generated or decoded
image buffers) are subloaded repeatedly to measure texture download
performance. Please note that textures widths and heights have to be 2^n and
have maximum size restrictions which are not imposed on Drawpixels. If your
data is not natively of a 2^n size, it is possible to zero-pad and adjust
texcoords appropriately. Or preferably, you could texsubimage the arbitaryly
sized image. 

H1. Conclusion
There are tradeoffs and benefits to using texture subloading over Drawpixels.
When chosen for the right reasons, texture subloading creates room for lots of
creative effects that would have been difficult to achieve with Drawpixels. 

H1. Example Application

texsub.c
===============================================================================
/*
 * jaya
 * for raw texture subload performance
 */

#include <stdio.h>
#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <sys/time.h>
#include <GL/glut.h>
#include <math.h>

long long now() {
    struct timeval tv;
    struct timezone tz;
    gettimeofday(&tv, &tz);
    return ((long long)tv.tv_sec) * 1e9 + ((long long)tv.tv_usec)*1e3;
}

GLenum texinternalformat,buftype,buformat;
GLubyte *buf,*buf2;
GLuint x,y,w,h,bsize,numiter,texName;
long long before,after;


void reshape(int w, int h) {
  glViewport(0,0,w,h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0,1,0,1,-1,+1);
}

static void init(void) {
  int i;
  GLubyte *obuf,*obuf2;
  
  buf = (GLubyte *) malloc(bsize*sizeof(GLubyte));
  buf2 = (GLubyte *) malloc(bsize*sizeof(GLubyte));

  obuf=buf;obuf2 =buf2;
  for (i=0; i < bsize; i++) {
    *(buf++) = 50;
    *(buf2++) = 90;
  }
  buf=obuf; buf2=obuf2;

  glClearColor(0,0,0,0);
  glShadeModel(GL_FLAT);
  glDisable(GL_DEPTH_TEST);
  glPixelStorei(GL_UNPACK_ALIGNMENT,1);
  glGenTextures(1,&texName);
  glBindTexture(GL_TEXTURE_2D, texName);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_REPLACE);
  glTexImage2D(GL_TEXTURE_2D,0,texinternalformat,w,h,0,buformat,buftype,buf);
  glEnable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, texName);
  glBegin(GL_QUADS);
  glTexCoord2f(0,0); glVertex3f(-2,-1,0);
  glTexCoord2f(0,1); glVertex3f(-2,1,0);
  glTexCoord2f(1,1); glVertex3f(2,1,0);
  glTexCoord2f(1,0); glVertex3f(2,-1,0);
  glEnd();
  fprintf(stderr,"err=%x\n",glGetError());
}


void display(void) {

  int i;
  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, buformat, buftype, buf);
  glBindTexture(GL_TEXTURE_2D, texName);
    glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex2f(0,0);
    glTexCoord2f(0,1); glVertex2f(1,0);
    glTexCoord2f(1,1); glVertex2f(1,1);
    glTexCoord2f(1,0); glVertex2f(0,1);
  glEnd();
  glFinish();
  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h, buformat, buftype, buf2);
  glBindTexture(GL_TEXTURE_2D, texName);
    glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex2f(0,0);
    glTexCoord2f(0,1); glVertex2f(1,0);
    glTexCoord2f(1,1); glVertex2f(1,1);
    glTexCoord2f(1,0); glVertex2f(0,1);
  glEnd();
  glFinish();

  before = now();
  for(i=0;i<numiter;i++) {
    if (i%2) {
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h,
                      buformat, buftype, buf);
    } else {
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w, h,
                      buformat, buftype, buf2);
    }

    glBindTexture(GL_TEXTURE_2D, texName);
    glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex2f(0,0);
    glTexCoord2f(0,1); glVertex2f(1,0);
    glTexCoord2f(1,1); glVertex2f(1,1);
    glTexCoord2f(1,0); glVertex2f(0,1);
    glEnd();
    glFinish();
  }
  after = now();
  
 { /* short term hack */
  double seconds = (double)(after - before)/1000000000.0;
  double mbytes = (double)(w*h*4*100)/(1024.0*1024.0);
  double bw = mbytes/ seconds;
  fprintf(stderr, "Aggregate bandwidth:  %4.2lf MB/sec\n", bw);
 }
  fflush(NULL);
  exit(0);
}


int main(int argc, char **argv) {
	
	switch(argc) {
	case 1: default:
		x=0;y=0;w=1024;h=512;numiter=100;bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 2:
		x=atoi(argv[1]);y=0;w=256;h=256;numiter=100;bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 3:
		x=atoi(argv[1]);y=atoi(argv[2]);w=256;h=256;numiter=100;
		bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 4:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=256;
		numiter=100;
		bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 5:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=100;
		bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 6:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=atoi(argv[5]);
		bsize=w*h*4;
		texinternalformat=GL_RGBA; buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 7:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=atoi(argv[5]);
		bsize=atoi(argv[6]);
		texinternalformat=GL_RGBA; 
		buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 8:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=atoi(argv[5]);
		bsize=atoi(argv[6]);
		texinternalformat=strtoul(argv[7],NULL,0); 
		buftype=GL_UNSIGNED_BYTE;
		buformat=GL_RGBA;
		break;
	case 9:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=atoi(argv[5]);
		bsize=atoi(argv[6]);
		texinternalformat=strtoul(argv[7],NULL,0); 
		buftype=strtoul(argv[8],NULL,0);
		buformat=GL_RGBA;
		break;
	case 10:
		x=atoi(argv[1]);y=atoi(argv[2]);w=atoi(argv[3]);h=atoi(argv[4]);
		numiter=atoi(argv[5]);
		bsize=atoi(argv[6]);
		texinternalformat=strtoul(argv[7],NULL,0); 
		buftype=strtoul(argv[8],NULL,0);
		buformat=strtoul(argv[9],NULL,0);
		break;
	}	

	glutInitWindowSize(w, h);
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutCreateWindow(argv[0]);
	init();
	glutReshapeFunc(reshape);
	glutDisplayFunc(display);
	glutMainLoop();
	return 0;
}